Command line (Unix)

Commands tips and examples:

Configuration

Conserver la configuration d'iptables lors des démarrages

# Sauvegarde de la configuration d'iptables dans un fichier
iptables-save > /etc/iptables.conf

# Création d'un fichier sh dans le dossier ...
echo "#!/bin/sh" > /etc/network/if-up.d/iptables

# ... qui restaurera les règles sauvegardé dans le fichier /etc/iptables.conf
echo "iptables-restore < /etc/iptables.conf" >> /etc/network/if-up.d/iptables
# Rendre executable le script bash
chmod +x /etc/network/if-up.d/iptables

Il est nécéssaire de relancer ce script à chaque modifications d'iptables

Gestion des services

(must be executable: chmod +x /etc/init.d/blah)

#! /bin/sh
# /etc/init.d/blah
## BEGIN INIT INFO
# Provides: blah
# Required-Start: $local_fs $syslog $remote_fs dbus
# Required-Stop: $local_fs $syslog $remote_fs
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Start blah
## END INIT INFO

# Some things that run always
touch /var/lock/blah

# Carry out specific functions when asked to by the system
case "$1" in
  start)
    echo "Starting script blah"
    echo "Could do more here"
    ;;
  stop)
    echo "Stopping script blah"
    echo "Could do more here"
    ;;
  *)
    echo "Usage: /etc/init.d/blah {start|stop}"
    exit 1
    ;;
esac

exit 0

Define when service have to be start or stop:

update-rc.d blah defaults

To remove from the startup sequence

update-rc.d -f blah remove

https://help.ubuntu.com/community/UbuntuBootupHowto
http://www.debian-administration.org/articles/28
man update-rc.d
http://en.wikipedia.org/wiki/Runlevel
http://www.debuntu.org/how-to-managing-services-with-update-rc-d/
List all runlevel for the service apache2: ls -l /etc/rc?.d/*apache2

User prompt

#!/bin/bash
echo "Yes,No?"
read answer
echo "You're answer: $answer"

http://www.tldp.org/LDP/Bash-Beginners-Guide/html/Bash-Beginners-Guide.html#sect_08_02_01

User management

# Set deadline for user password
chage -E 2005-12-31 user1

# Create a new group
groupadd [group]

# Delete a group
groupdel [group]

# Rename a group from moon to sun
groupmod -n moon sun

# Check correct syntax and file format of `/etc/group` and groups existence
grpck

# Log into a new group to change default group of newly created files
newgrp - [group]

# Change password
passwd
# Change a user password (only by root)
passwd user1

# Check correct syntax and file format of `/etc/passwd` and users existence
pwck

# Create a new user `user1` belongs `admin` group
useradd -c "User Linux" -g admin -d /home/user1 -s /bin/bash user1

# Create a new user
useradd user1

# Delete a user (`-r` eliminates home directory)
userdel -r user1

# Change user attributes as description, group and other
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1

# Show user rights on files
ls -l
# or, but show folders "." and ".."
ls -all

# User informations
id USERNAME

# Show last logs of users
lastlog

# Show last logged users
last

# Show current user
who -a

# Command history
~/.bash_history
~/.history
# for root user
/root/.bash_history

# Be sure no user can hide his command history (a = append only, i = immutable)
chattr +a /home/user/.bash_history
chattr +i /home/user/.profile
# See also
# http://www.akyl.net/securing-bashhistory-file-make-sure-your-linux-system-users-won%E2%80%99t-hide-or-delete-their-bashhistory
# http://zero202.free.fr/bash/html/ar01s01.html#id336074

# https://en.wikipedia.org/wiki/Chattr
chattr
chwon
chmod

Network

Note: ifconfig, route, mii-tool, nslookup commands are obsolete

# Show status of ethernet interface eth0
ethtool eth0
#Manually set ethernet interface speed
ethtool --change eth0 autoneg off speed 100 duplex full

# Show link status of `eth0`
mii-tool eth0

# Show configuration of an ethernet network card
ifconfig eth0
# Configure IP Address
ifconfig eth0 192.168.1.1 netmask 255.255.255.0
# Configure `eth0` in promiscuous mode to gather packets (sniffing)
ifconfig eth0 promisc
# Show status of wireless interface eth1
iwconfig eth1
# Manually set wireless interface speed
iwconfig eth1 rate 1Mb/s fixed

# List wireless networks in range
iwlist scan

# Disable an interface `eth0`
ifdown eth0
# Activate an interface `eth0`
ifup eth0

# List network interfaces and their status
ip link show
# Rename interface eth0 to wan
ip link set dev eth0 name wan
# Bring interface eth0 up (or down)
ip link set dev eth0 up
# List addresses for interfaces
ip addr show
# Add (or del) ip and mask (255.255.255.0)
ip addr add 1.2.3.4/24 brd + dev eth0
# List routing table
ip route show
# Set default gateway to 1.2.3.254
ip route add default via 1.2.3.254

# Show routing table
route -n
# Configure default gateway
route add -net 0/0 gw IP_Gateway
# Configure static route to reach network `192.168.0.0/16`
route add -net 192.168.0.0 netmask 255.255.0.0 gw 192.168.1.1
# Remove static route
route del 0/0 gw IP_gateway

# Lookup DNS ip address for name or vice versa
host example.com

# Machine name
hostname
# Lookup local ip address (equivalent to host `hostname`)
hostname -i

# Active interface `eth0` in dhcp mode
dhclient eth0

# List network services on a system and their PID
netstat -tupl
# List active network connections to/from system and their PID
netstat -tup
# Show routing table alike "route -n"
netstat -rn

# Show all HTTP traffic
tcpdump tcp port 80

# DNS record
dig example.com

# Lookup whois info for hostname or ip address
whois example.com

# Activate ip routing temporarily
echo "1" > /proc/sys/net/ipv4/ip_forward

# Reverse DNS
ping -a 8.8.8.8
nslookup -type=ptr 8.8.8.8
nslookup www.example.com

# Test if remote port is open
nc -vz example.com 80
nmap -p 80 example.com
telnet example.com 80
timeout 1 bash -c "</dev/tcp/example.com/80" && echo Port open || echo Port closed

/etc/hostname /etc/hosts

Configurer une passerelle réseau — Korben Wiki

Windows networking

Note: samba is the package that provides all this windows specific networking support

# Find windows machines. See also findsmb
smbtree

# Find the windows (netbios) name associated with ip address
nmblookup -A 1.2.3.4

# List shares on windows machine or samba server
smbclient -L windows_box
# Show remote shares of a windows host
smbclient -L ip_addr/hostname

# Mount a windows share
mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/share

# Send popup to windows machine (off by default in XP sp2)
echo 'message' | smbclient -M windows_box

# Mount a windows network share
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share

# Netbios name resolution
nbtscan ip_addr

# Netbios name resolution
nmblookup -A ip_addr

# Like wget can download files from a host windows via smb
smbget -Rr smb://ip_addr/share

HTTP

# Get headers
curl -s -D - https://example.com -o /dev/null
# Raw body
curl -s --ignore-content-length --raw https://example.com

# Get HTTP response
echo -en "GET /feed/ HTTP/1.1\r\nHost:example.com\r\nUser-Agent:Firefox\r\n\r\n" | nc infoheap.com 80
# Get the header Content-Type
echo -en "GET /feed/ HTTP/1.1\r\nHost:example.com\r\nUser-Agent:Firefox\r\n\r\n" | nc localhost 80 | head -n 30 | grep -a Content-Type
# Search if test is in first 1000 bytes (include header)
echo -en "GET /feed/ HTTP/1.1\r\nHost:example.com\r\nUser-Agent:Firefox\r\n\r\n" | nc localhost 80 | head -c1K | grep -a test
# Get body length
echo -e "GET / HTTP/1.1\r\nHost: example.com\r\nAccept-Encoding: gzip, deflate\r\n\r\n" | nc localhost 80 | sed ':a;N;$!ba;s/^.*\r\n\r\n//g' | wc -c
# Get body uncompressed length (should be gzipped)
echo -e "GET / HTTP/1.1\r\nHost: example.com\r\nAccept-Encoding: gzip, deflate\r\n\r\n" | nc 93.184.216.34 80 | sed ':a;N;$!ba;s/^.*\r\n\r\n//g' | gzip -d | wc -c

# Simple HTTP server
echo -e "GET / HTTP/1.1\r\nHost:example.com\r\nUser-Agent:Firefox\r\n\r\n" | nc example.com 80 > response.http
while true; do nc -l 8000 < response.http; done

# Create `.htpasswd` file
htpasswd -c /path/.htpasswd USERNAME

How to display request headers with command line curl - Stack Overflow

wget

Multi purpose download tool

# Store local browsable version of a page to the current dir
(cd dir/ && wget -nd -pHEKk http://www.pixelbeat.org/cmdline.html)

# Continue downloading a partially downloaded file (with the ability to stop the download and resume later)
wget -c http://www.example.com/large.file

# Download a set of files to the current directory
wget -r -nd -np -l1 -A '*.jpg' http://www.example.com/dir/

# FTP supports globbing directly
wget ftp://remote/file[1-9].iso/

# Process output directly
wget -q -O- http://www.pixelbeat.org/timeline.html | grep 'a href' | head

# Download url at 1AM to current dir
echo 'wget url' | at 01:00

# Do a low priority download (limit to 20KB/s in this case)
wget --limit-rate=20k url

# Check links in a file
wget -nv --spider --force-html -i bookmarks.html

# Efficiently update a local copy of a site (handy from cron)
wget -m http://www.example.com/
wget -m -U "" http://example.com/path/dir

SSH Tunnel

# Redirect local port to a remote machine
ssh -NfL 8080:127.0.0.1:0808 user@host

Set Up SSH Tunneling on a Linux / Unix / BSD Server To Bypass NAT - nixCraft

Backup external server

Use rsync if possible, or lftp, curl, wget, scp, sftp. See also unison, bacula or amanda

Copy files over SSH

scp /path/localfile user@host:/path/remotefile

scp /path/localfile user@host:/path/remotedir/

scp /path/localdir user@host:/path/remotedir

scp -i /home/username/.ssh/id_rsa -r -p username@www.mydomain.tld:/ /dst/dir

Copy files over SSH shell

# Copy content of a directory on remote directory via ssh
( cd /tmp/local/ && tar c . ) | ssh -C user@ip_addr 'cd /home/share/ && tar x -p'

# Copy a local directory on remote directory via ssh
( tar c /home ) | ssh -C user@ip_addr 'cd /home/backup-home && tar x -p'

Copy files with `sftp`

sftp -i /path/to/private/keyfile remote.host.tld

Copy files with `lftp`

/dst/dir.lftp:

set ftp:list-options -a
#set cmd:fail-exit true
# To use keyfile
# http://www.adminschoice.com/how-to-configure-ssh-without-password
# ssh-keygen -t rsa -f keyfile -N ""
#set sftp:connect-program "ssh -a -x -i <keyfile>"
open -u user,pass sftp://sftp.dc0.gpaas.net
mirror --verbose --delete --parallel=4 --only-newer --exclude ^snapshots/ --exclude ^vhosts/ --exclude ^lamp0/\.config --exclude ^lamp0/var/admin/gandi.cnf$ --exclude ^lamp0/var/admin/logrotate.conf$ --exclude ^lamp0/var/cron/admin/logrotate$ --exclude ^lamp0/var/cron/admin/phpsess$ --exclude ^lamp0/db/ --exclude ^lamp0/var/log/.+ --exclude ^lamp0/var/php/www/.+ "${SRC_DIR}" "${DST_DIR}"
exit

# For paths in variables used in sed, see https://stackoverflow.com/a/29613573/470117
SRC_DIR=/src/dir; DST_DIR=/dst/dir; sed -e "s#\${SRC_DIR}#$SRC_DIR#" -e "s#\${DST_DIR}#$DST_DIR#" /dst/dir.lftp | lftp -f /dev/stdin

lftp -u username,password ftphost << EOF
mirror -Re --use-cache /home/ /backup/
mirror -Re --use-cache /etc/ /backup/
mirror -Re --use-cache /var/www/ /backup/
quit 0
EOF

--exclude / -x use extended regular expression (see egrep) \.nfo. Folders path don't start with slash, but have a trailing slash: etc/bin/

Add --reverse to restore backup

For lftp –> Fatal error: Certificate verification: Not trusted:

mkdir -p /root/.lftp
echo "set ssl:verify-certificate no" >> /root/.lftp/rc

https://linux.die.net/man/1/lftp
http://mewbies.com/lftp_basic_usage_tutorial.htm
linux - Transfer files using lftp in bash script - Stack Overflow
Fastest segmented parallel sync of a remote directory over ssh | commandlinefu.com
~/.lftp.rc parameters detailed
Shell scripting and LFTP | A Pipe and a Keyboard
How to store lftp command result to a variable
calling lftp from a bash script; howto pass variables into the command syntax

Copy files from FTP with `wget`

Use a .wgetrc file to store configuration

/dst/dir.wget:

# Credentials
ftp_user=user
ftp_password=password
# Other commands
exclude_directories=/snapshots,/vhosts,/lamp0/.config,/lamp0/db,/lamp0/var/log,/lamp0/var/php/www
#reject=.listing
#cut_dirs=0
quiet=on
no_parent=on
mirror=on
add_hostdir=off
#retr_symlinks=on

cd /dst/dir
WGETRC=/dst/dir.wget wget ftp://www.mydomain.tld/
# Clean up obselete files
find . -name ".listing" -type f -exec bash -c 'cd $(dirname "{}"); find . -maxdepth 0 ! -name ".listing" -printf "%P\n" | fgrep -vf ".listing" | while read file; do rm $(basename "$file"); done;' \;
# find .-name ".listing" -type f  -exec bash -c 'cd $(dirname "{}"); find . -maxdepth 0 ! -name ".listing" -printf "%P\n" | fgrep -vf ".listing" | xargs -r rm' \;

Note: if you set password in URL don't forget to encode special chars: mypass#gh647 to mypass%23gh647

GNU Wget 1.20 Manual

Copy files with `rsync`

Network efficient file copier

Handling renamed files or directories in rsync - Server Fault

Use the --dry-run option for testing

# Synchronization between directories
rsync -rogpav --delete /home /tmp

# Rsync via SSH tunnel
rsync -rogpav -e ssh --delete /home ip_address:/tmp

# Synchronize a local directory with a remote directory via SSH and compression
rsync -az -e ssh --delete ip_addr:/home/public /home/local

# Synchronize a remote directory with a local directory via SSH and compression
rsync -az -e ssh --delete /home/local ip_addr:/home/public

# Copy as archive (oneway, for backup)
rsync -a username@www.mydomain.tld:/ /dst/dir

rsync -r -t -v /path/srcdir /path/destdir
rsync -r -t -v /path/srcdir remote:~/My\ documents
# Escape spaces, and keep special char interpreted at the destination. See "How to rsync over ssh when directory names have spaces - Unix & Linux Stack Exchange" https://unix.stackexchange.com/questions/104618/how-to-rsync-over-ssh-when-directory-names-have-spaces
DEST="~/My\ documents"; rsync -r -t -v /path/srcdir "remote:${DEST// /\\ }"

# Only get diffs. Do multiple times for troublesome downloads
rsync -P rsync://rsync.server.com/path/to/file file

# Locally copy with rate limit. It's like nice for I/O
rsync --bwlimit=1000 fromfile tofile

# Mirror web site (using compression and encryption)
rsync -az -e ssh --delete ~/public_html/ remote.com:'~/public_html'

# Synchronize current directory with remote one
rsync -auz -e ssh remote:/dir/ . && rsync -auz -e ssh . remote:/dir/
date=$(date +%Y%m%d-%H%M)
#[for loop over users]
older=( $backups/$user/*(N/om) )
rsync --archive --recursive \
	--fuzzy --partial --partial-dir=$backups/$user/.rsync-partial \
	--log-file=$tempfile --link-dest=${^older[1,20]} \
	--files-from=$configdir/I-$user \
	--exclude-from=$configdir/X-$user \
	$user@$from:/ $backups/$user/$date/

# Copy folder to folder (if mounted)
rsync -ah --progress --exclude='$RECYCLE.BIN' --exclude='$Recycle.Bin' --exclude='.AppleDB' --exclude='.AppleDesktop' --exclude='.AppleDouble' --exclude='.com.apple.timemachine.supported' --exclude='.dbfseventsd' --exclude='.DocumentRevisions-V100*' --exclude='.DS_Store' --exclude='.fseventsd' --exclude='.PKInstallSandboxManager' --exclude='.Spotlight*' --exclude='.SymAV*' --exclude='.symSchedScanLockxz' --exclude='.TemporaryItems' --exclude='.Trash*' --exclude='.vol' --exclude='.VolumeIcon.icns' --exclude='Desktop DB' --exclude='Desktop DF' --exclude='hiberfil.sys' --exclude='lost+found' --exclude='Network Trash Folder' --exclude='pagefile.sys' --exclude='Recycled' --exclude='RECYCLER' --exclude='System Volume Information' --exclude='Temporary Items' --exclude='Thumbs.db' /src/dir/ /dst/dir/

# With exlude list `--exclude-from=exclude-list.txt`:
cat > exclude-list.txt << 'EOF'
# https://alexkaloostian.com/2015/01/22/what-are-all-these-hidden-items-on-my-mac-part-1/
# http://superuser.com/questions/180582/what-are-desktop-db-or-desktop-df-files-on-external-hd
# http://forum.mac4ever.com/pourquoi-t73534.html#p997828
# http://netatalk.sourceforge.net/wiki/index.php/Special_Files_and_Folders
# Apple OS
.AppleDouble
.com.apple.timemachine.donotpresent
.com.apple.timemachine.supported
.Spotlight-V100
.DocumentRevisions-V100
.DS_Store
.Trash
.Trashes
.VolumeIcon.icns
._.Trashes
.fseventsd
.dbfseventsd
.metadata_never_index
.LSOverride
.MobileBackups
.TemporaryItems
.file
.hotfiles.btree
.quota.ops.user
.quota.user
.quota.ops.group
.quota.group
.vol
.PKInstallSandboxManager
.PKInstallSandboxManager-SystemSoftware
# Max OS6-9
Desktop DB
Desktop DF
# AFP
.AppleDB
.AppleDesktop
Temporary Items
Network Trash Folder
.apdisk
# Sherlock files Mac OS 8.5 to OSX 10.3
TheFindByContentFolder
TheVolumeSettingsFolder
.FBCIndex
.FBCSemaphoreFile
.FBCLockFolder
# http://apple.stackexchange.com/questions/14980/why-are-dot-underscore-files-created-and-how-can-i-avoid-them
# https://en.wikipedia.org/wiki/AppleSingle_and_AppleDouble_formats
# See also dot_clean command
#._*

# Linux
lost+found

# Windows
$RECYCLE.BIN
$Recycle.Bin
Thumbs.db
ehthumbs.db
ehthumbs_vista.db
pagefile.sys
hiberfil.sys
desktop.ini
Recycled
RECYCLER
System Volume Information

# Other
.SymAV*
.symSchedScanLockxz

# Package manager cache
node_modules
EOF

Resources for exclude metadata and system files:

https://github.com/github/gitignore
https://github.com/joeblau/gitignore.io/tree/master/data
https://gist.github.com/keithmorris/c652b2a4d88788e5416d
https://github.com/dotphiles/dotphiles/blob/master/git/gitignore
Rsync --exclude List for Mac OS X - Alan W. Smith
rsync on OS X says its complete but it's really not? : unix

Math

# Quick math (Calculate φ). See also bc
echo '(1 + sqrt(5))/2' | bc -l

# Calculate π the unix way
seq -f '4/%g' 1 2 99999 | paste -sd-+ | bc -l

# More complex (int) e.g. This shows max FastE packet rate
echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bc

# Python handles scientific notation
echo 'pad=20; min=64; print (100E6)/((pad+min)*8)' | python

# Plot FastE packet rate vs packet size
echo 'pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)' | gnuplot -persist

# Base conversion (decimal to hexadecimal)
echo 'obase=16; ibase=10; 64206' | bc

# Base conversion (hex to dec) ((shell arithmetic expansion))
echo $((0x2dec))

# Unit conversion (metric to imperial)
units -t '100m/9.58s' 'miles/hour'

# Unit conversion (SI to IEC prefixes)
units -t '500GB' 'GiB'

# Definition lookup
units -t '1 googol'

# Add a column of numbers. See also add and funcpy
seq 100 | (tr '\n' +; echo 0) | bc

Date and clock

# Display a calendar
cal -3

# Display a calendar for a particular month year
cal 9 1752

# System date
date

# Set system date and time `MonthDayhoursMinutesYear.Seconds`
date 041217002020.00

# save date changes on BIOS
clock -w

# What date is it this friday. See also day
date -d fri

# Exit a script unless it's the last day of the month
[ $(date -d '12:00 +1 day' +%d) = '01' ] || exit

# What day does xmas fall on, this year
date --date='25 Dec' +%A

# Convert seconds since the epoch (1970-01-01 UTC) to date
date --date='@2147483647'

# What time is it on west coast of US (use tzselect to find TZ)
TZ='America/Los_Angeles' date

# What's the local time for 9AM next Friday on west coast US
date --date='TZ="America/Los_Angeles" 09:00 next Fri'

Locale

# Print number with thousands grouping appropriate to locale
printf "%'d\n" 1234

# Use locale thousands grouping in ls. See also l
BLOCK_SIZE=\'1 ls -l

# Extract info from locale database
echo "I live in $(locale territory)"

# Lookup locale info for specific country. See also ccodes
LANG=en_IE.utf8 locale int_prefix

# List fields available in locale database
locale -kc $(locale | sed -n 's/\(LC_.\{4,\}\)=.*/\1/p') | less

Packages

RPM Packages ( Fedora, Red Hat and like):

# install a rpm package
rpm -ivh [package.rpm]

# install a rpm package ignoring dependencies requests
rpm -ivh --nodeeps [package.rpm]

# upgrade a rpm package without changing configuration files
rpm -U [package.rpm]

# upgrade a rpm package only if it is already installed
rpm -F [package.rpm]

# remove a rpm package
rpm -e [package]

# show all rpm packages installed on the system
rpm -qa

# show all rpm packages with the name "httpd"
rpm -qa | grep httpd

# obtain information on a specific package installed
rpm -qi [package]

# show rpm packages of a group software
rpm -qg "System Environment/Daemons"

# show list of files provided by a rpm package installed
rpm -ql [package]

# show list of configuration files provided by a rpm package installed
rpm -qc [package]

# show list of dependencies required for a rpm packet
rpm -q [package] --whatrequires

# show capability provided by a rpm package
rpm -q [package] --whatprovides

# show scripts started during installation / removal
rpm -q [package] --scripts

# show history of revisions of a rpm package
rpm -q [package] --changelog

# verify which rpm package belongs to a given file
rpm -qf /etc/httpd/conf/httpd.conf

# show list of files provided by a rpm package not yet installed
rpm -qp [package.rpm] -l

# import public-key digital signature
rpm --import /media/cdrom/RPM-GPG-KEY

# verify the integrity of a rpm package
rpm --checksig [package.rpm]

# verify integrity of all rpm packages installed
rpm -qa gpg-pubkey

# check file size, permissions, type, owner, group, MD5 checksum and last modification
rpm -V [package]

# check all rpm packages installed on the system - use with caution
rpm -Va

# verify a rpm package not yet installed
rpm -Vp [package.rpm]
- `rpm -ivh /usr/src/redhat/RPMS/`arch`/[package.rpm]`: install a package built from a rpm source

# extract executable file from a rpm package
rpm2cpio [package.rpm] | cpio --extract --make-directories *bin*

# build a rpm package from a rpm source
rpmbuild --rebuild [package.src.rpm]

# List all packages by installed size (Bytes) on rpm distros
rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n

YUM packages tool (Fedora, RedHat and alike):

# download and install a rpm package
yum -y install [package]

# That will install an RPM, and try to resolve all the dependencies for you using your repositories.
yum localinstall [package.rpm]

# update all rpm packages installed on the system
yum -y update

# upgrade a rpm package
yum update [package]

# remove a rpm package
yum remove [package]

# list all packages installed on the system
yum list

# find a package on rpm repository
yum search [package]

# clean up rpm cache erasing downloaded packages
yum clean [package]

# remove all files headers that the system uses to resolve dependency
yum clean headers

# remove from the cache packages and headers files
yum clean all

DEB packages (Debian, Ubuntu and like):

# install / upgrade a deb package
dpkg -i [package.deb]

# remove a deb package from the system
dpkg -r [package]

# show all deb packages installed on the system
dpkg -l

# show all deb packages with the name "httpd"
dpkg -l | grep httpd

# obtain information on a specific package installed on system
dpkg -s [package]

# show list of files provided by a package installed on system
dpkg -L [package]

# show list of files provided by a package not yet installed
dpkg --contents [package.deb]

# verify which package belongs to a given file
dpkg -S /bin/ping

# List all packages by installed size (KBytes) on deb distros
dpkg-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n

APT packages tool (Debian, Ubuntu and alike):

# returns list of packages which corresponds string "searched-packages"
apt-cache search [package]

# install / upgrade a deb package from cdrom
apt-cdrom install [package]

# install / upgrade a deb package
apt-get install [package]

# update the package list
apt-get update

# upgrade all of the installed packages
apt-get upgrade

# remove a deb package from system
apt-get remove [package]

# verify correct resolution of dependencies
apt-get check

# clean up cache from packages downloaded
apt-get clean

Pacman packages tool (Arch, Frugalware and alike):

# Install package `name` with dependencies
pacman -S name

# Delete package `name` and all files of it
pacman -R name

Monitoring and debugging

fuser
lsof
ls -l  /proc/[process id]/fd
ls -l  /proc/*/fd
for p in [0-9]*; do ls -l /proc/$p/fd ;done
strace ls
someexe > /dev/null & sudo dtruss -f -t open -p $!
inotifywait -m -r -e OPEN /path/to/traced/directory

# Displays status of RAM in megabytes
free -m

# Force closure of the process and finish it
kill -9 process_id

# force a process to reload configuration
kill -1 process_id

# Show history reboot
last reboot

# Display kernel loaded
lsmod

# Display a list of files opened by processes
lsof -p process_id

# Displays a list of open files in a given path system
lsof /home/user1

# Displays linux tasks
ps -eafw

# Displays linux tasks in a hierarchical mode
ps -e -o pid,args --forest

# Shows a tree system processes
pstree

# Monitoring reliability of a hard-disk through SMART
smartctl -A /dev/hda

# Check if SMART is active on a hard-disk
smartctl -i /dev/hda

# Display system calls made and received by a process
strace -c ls >/dev/null

# Display library calls
strace -f -e open ls >/dev/null

# Show events inherent to the process of booting kernel
tail /var/log/dmesg

# Show system events
tail /var/log/messages

# Display linux tasks using most cpu
top

# Display interrupts in real-time
watch -n1 'cat /proc/interrupts'

# Show shared libraries required by ssh program
ldd /usr/bin/ssh

# See also
auditctl
inotify

# Get process details for process ID 3117
/proc/3117

# Monitor messages in a log file
tail -f /var/log/messages

# Summarise/profile system calls made by command
strace -c ls >/dev/null

# Show file opens
echo exit | strace bash -li |& grep '^open'

# List system calls made by command
strace -f -e open ls >/dev/null

# Monitor what's written to stdout and stderr
strace -f -e trace=write -e write=1,2 ls >/dev/null

# List library calls made by command
ltrace -f -e getenv ls >/dev/null

# List opened files and ports
# http://en.wikipedia.org/wiki/Lsof
lsof

# List paths that process id has open
lsof -p $$

# List processes that have specified path open
lsof ~

# Show network traffic except ssh. See also tcpdump_not_me
tcpdump not port 22

# List processes in a hierarchy
ps -e -o pid,args --forest

# List processes by % cpu usage
ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'

# List processes by mem (KB) usage. See also ps_mem.py
ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS

# List all threads for a particular process
ps -C firefox-bin -L -o pid,tid,pcpu,state

# List elapsed wall time for particular process IDs
ps -p 1,$$ -o etime=

# Show system reboot history
last reboot

# Show amount of (remaining) RAM (-m displays in MB)
free -m

# Watch changeable data continuously
watch -n.1 'cat /proc/interrupts'

# Monitor udev events to help configure rules
udevadm monitor

# Active processes
ps -A

# Active processes - Tree processes
/bin/ps acxfwwwe

# Active processes - Live display
top

# List active network connections (TCP) with corresponding processes
netstat -ape

System

System information

Power management

Aka shutdown, restart and logout of a system

# shutdown system(2)
init 0

# leaving session
logout

# reboot(2)
reboot

# shutdown system(1)
shutdown -h now

# planned shutdown of the system at 16:30
shutdown -h 16:30 &

# cancel a planned shutdown of the system
shutdown -c

# reboot
shutdown -r now

# shutdown system
telinit 0

Interactive

Shell

Command-line interface (CLI), not for graphical user interface (GUI)

The default shell is defined for a specific user by the file /etc/passwd

# List available shells
cat /etc/shells

# Clear shell cache
hash -r

# Change shell
chsh
chsh --list-shells

In /etc/bashrc or ~/.bashrc

# If id command returns zero, you’ve root access.
if [ $(id -u) -eq 0 ];
then you are root, set red colour prompt
	PS1="\\[$(tput setaf 1)\\]\\u@\\h:\\w\\[$(tput sgr0)\\]"
else normal
	PS1="[\\u@\\h:\\w] $"
fi

Shells:

Bash (Unix shell) - Wikipedia - Bourne-Again shell
Bourne shell - Wikipedia
Z shell - Wikipedia

Shell config

# Display current shell prompt setting
echo $PS1
# Change current shell prompt setting
export PS1="..."
export PS1="\[\033[0m\]\[\033[0;30;47m\] \u\[\033[0m\]\[\033[0;30;47m\]@\h\[\033[0m\] \w\n\[\033[1;32m\] \@ \$ \[\033[0m\]"
export PS1="[${LOGNAME}@$(hostname)]"

Profile files, defined by (in order, but also if the shell is interactive and/or a login):

(global system) /etc/profile
(global system) /etc/bashrc
(user) ~/.bash_profile
(user) ~/.bash_login
(user) ~/.profile
(user) ~/.bashrc (not used by some OS like macOS for login shell, it's recommended to if [ -s ~/.bashrc ]; then source ~/.bashrc; fi in ~/.profile for that case)
(user) ~/.bash_logout au logout

(and /etc/bash.bashrc, /etc/bash.bashrc.local?)

To reload a configuration file (here the file ~/.bashrc)

source ~/.bashrc
# or use dot command:
. ~/.bashrc

initialisation at the session level (.bash_profile) and initialisation at each shell level (.bashrc)

By convention, the prompt ends with $ for users and by # for root

Command alias

# quick dir listing
alias l='ls -l --color=auto'

Programmable bash completions

See complete buildin command

Terminal history auto complete

In ~/.inputrc or /etc/inputrc:

# History auto complete with "start with" filter
"\e[5~": history-search-backward
"\e[6~": history-search-forward
set show-all-if-ambiguous on
set completion-ignore-case on

http://www.gnu.org/software/bash/manual/html_node/Readline-Init-File.html
https://stackoverflow.com/questions/1030182/how-do-i-change-bash-history-completion-to-complete-whats-already-on-the-line

On OSX Page up and Page down in Terminal are by default use to manipulat buffer instead to send key stroke

You can change it in Preferences → Settings → Keyboard:

Page down : \033[6~
Page up : \033[5~
End : \033OF (works in vi, vim, etc.) ou \033[4~, \033[F, \005
Home : \033OH (works in vi, vim, etc.) ou \033[1~, \033[H, \001

Use esc to type these strings (add \033 in input field) or past (via the context menu)

Shell variables

env

Colors and control sequences

For ls colors:

export CLICOLOR=1
export TERM=xterm-color
export LSCOLORS=DxFxcxdxBxegedbxHxacHd

key=effect;foreground colour;background colour separated by :.

Ex.: a symlink bright pink ln=01;95;40 give:

export LS_COLORS="di=01;33;40:ln=01;95;40"

To known color config:

man ls

#
# Dont forget to call ~/.bashrc in your ~/.profile script
#

export CLICOLOR=1
alias ll='ls -l'
alias la='ls -A'
alias vi='vim'
alias l='ls -CF'

function cyan_red_prompt {
	local CYAN="\[\033[0;36m\]"
	local GRAY="\[\033[0;37m\]"
	local RED="\[\033[0;31m\]"
	PS1="${CYAN}[\u@\h ${RED}\w${CYAN}]${GRAY} "
}

cyan_red_prompt

Mouse position and click

Aka mouse tracking escape sequences

Command arguments

usage() {
	cat <<EOT
Usage: ${basename $0} [-a value] [-h] value...

Options:
-h          Print this help
-a value    Print something
EOT
}

while getopts ":ha:" opt; do
	case $opt in
		a)
			echo "-a with value: $OPTARG"
			;;
		h)
			usage
			exit 0
			;;
		\?)
			echo "Invalid option: -$OPTARG" >&2
			usage
			exit 1
			;;
		:)
			echo "Option -$OPTARG requires an argument." >&2
			usage
			exit 1
			;;
	esac
done

shift $((OPTIND-1))

others=($@)

echo "${others[@]}"
echo "$@"

Command alias

alias NICKNAME='COMMAND -withargs'

A ajouter dans ~/.bashrc

Create cmd aliases in Windows | Displayobject

Shell script file

Note: take care editing bash scripts

Create a shell script file.sh the execute the following command to allow it to be executable:

chmod +x /path/to/file.sh

Start with the shebang #!/bin/sh, which indicate the script interpreter (sh, php, python, perl, node, etc.) or for portability, use env:

#!/usr/bin/env sh
echo Hello world!

Or detect the right interpreter with an additional line, here to use nodejs or node. : command in bash is noop.

#!/usr/bin/env sh
':' //; exec "$(command -v nodejs || command -v node)" "$0" "$@"

console.log('Hello world!');

To include shell script into an other:

# Relative to execution path:
#source /path/to/script.sh
# So use this instead:
source $(dirname $0)/script.sh
# Or:
CURRENT_DIR=`dirname $0`
$CURRENT_DIR/script.sh

Shell script syntax

Use $( ), and don't use `` anymore: Bash FAQ 82.

Avoid using UPPERCASE variable names. That namespace is generally reserved by the shell for special purposes (like PATH), so using it for your own variables is a bad idea.

Escape special char in argument:

command $'\t'

Wildcard files:

for file in *.ext1; do echo "${file} ${file/.ext1/.ext2}"; done

ls file_*{.png,.jpg}

File Wildcards

Brace expansion

sudo mv /path/file{,.old}
sudo ln {/path1,/path2}/file

Bash Reference Manual: Brace Expansion

Strings:

echo "The current user (\$USER) \"$USER\" use the shell (\$SHELL) \"$SHELL\""
echo 'The current user ($USER) "'"$USER"'" use the shell ($SHELL) "'"$SHELL"'"'

Shell parameter expansion:

# Remove trailing slash for all arguments `a/ b/c/ d /` output `a b/c d`
echo ${@%/}

# myvar=a/b/// output `a/b`
shopt extglob
echo ${myvar%%+(/)}

somevar=$(echo "$value" | sed 's:/*$::')
echo $somebar

dir=/a/b///
echo $(realpath -s --canonicalize-missing $dir)

# Construct command parts as an array
mycommand=(/some/command "$PATH_NAME")
# Print the command
printf '%s\n' "${mycommand[*]}"
# Execute command
"${mycommand[@]}"

Redirection

File pointer and file redirection

while read item; do
	echo $item
done < sql.res

Bash support process substitution:

cat <(echo "tmp file content")

Is similar to: echo hello > file; cat file; rm file

$(cat file) is same as $(< file)

cat <<< hello

diff <(cd dir1; ls) <(cd dir2; ls)

(
	echo open ip_address
	echo user username password
	echo put -O $today $file_gnome_curr
	echo bye
) | lftp -f /dev/stdin >> lftp.log 2>&1

Here-doc & here-string:

cat > /path/to/file <<EOF
Some thing.
Blahblah!
$somevar
EOF

cat > /path/to/file <<< "Some thing."

cat <<EOF
test1
test2
EOF

(cat <<'EOF'
file1
file2
EOF
) | while read -r file; do
	cp "from/$file" "to/$file";
done;

cat <<EOF >> greetings.txt
line 1
line 2
EOF

# Here-doc to var
# Use `IFS=` otherwise any leading and trailing spaces will be trimmed
# Use `<<'EOF'` instead `<<EOF` to ignore variables tokens
IFS= read -r -d '' MYVAR <<'EOF'
abc'asdf"
$(dont-execute-this)
foo"bar"''
EOF

How to assign a heredoc value to a variable in Bash? - Stack Overflow

File descriptors (fd) :

0 is stdin IN
1 is stdout OUT
2 is stderr ERROR

2>&1 redirects fd 2 to 1 (stderr to stdout)

# Empty a file (ex: clean a log file)
> /var/log/apache2/error.log

# Append to a file
echo "Appended text" >> /path/file

# Log all infos (and erros) of following commands to a file `/tmp/log.txt`
( /bin/ps acxfwwwe 2>&1; /usr/sbin/lsof -Pwln 2>&1; /bin/netstat -anpe 2>&1; /usr/bin/lastlog 2>&1; /usr/bin/last 2>&1; /usr/bin/who -a 2>&1 ) > /tmp/log.txt

man -P less\ +/^REDIRECTION bash
http://www.tldp.org/LDP/Bash-Beginners-Guide/html/Bash-Beginners-Guide.html#sect_08_02_03_02
In the bash shell, what is "2>&1"
/usr/include/unistd.h
http://en.wikipedia.org/wiki/File_descriptor
bash - How to pipe stderr, and not stdout? - Stack Overflow
Why stdout is faster than stderr? - Orhun's Blog

Pipe:

Pipeline (Unix) — Wikipedia

Network with redirection

Use instead specialized tools like netcat or socat

/dev/tcp/<host>/<port> and /dev/udp/<host>/<port>
{ echo -e "GET / HTTP/1.0\r\nHost: www.example.com\r\n\r" >&3; cat <&3 ; } 3<> /dev/tcp/www.example.com/80
bash - /dev/tcp listen instead of nc listen - Unix & Linux Stack Exchange - port listing is not possible
Bash Reference Manual
GitHub - caquino/redis-bash: REDIS-BASH - Bash library to access Redis - Example of what can be made with network redirection

Fork process

Execute in background

If a command is terminated by the control operator &, the shell executes the command in the background in a subshell

echo '' > .mycmd.pid
mycmd & echo "$!" >> .mycmd.pid
# ... later
cat .mycmd.pid | xargs -n 1 kill -9

Add a bin folder to global executables

Pour éviter de tapper le chemin entier vers les commandes / executables

PATH=$PATH:/path/bindir
export PATH

PATH=$PATH:/path/bindir command-use-path
PATH=$PATH:/path/bindir bash -c 'echo $PATH'
PATH=$PATH:/path/bindir bash -c 'command1 | command2'
(export PATH=$PATH:/path/bindir; command1 | command2)

Pour l'ajouter de façon permanente, l'écrire dans ~/.profile ou ~/.bashrc

Path (variable) - Wikipedia

Automatic error detection

Instead || exit 1 after each important command.

Why doesn't set -e (or set -o errexit, or trap ERR) do what I expected?

Dotfiles

mathiasbynens/dotfiles: .files, including ~/.macos — sensible hacker defaults for macOS

# Enter to directory `/home`
cd /home
# Go back one level
cd ..
# Go back two levels
cd ../..
# Go to $HOME directory
cd
# Go to home directory
cd ~user1
# Go to previous directory
cd -

# Get the current working directory
pwd

# Go to dir, execute command and return to current dir
(cd dir && command)

# Put current dir on stack so you can popd back to it
pushd .

Files and folders operations

File name:

Using sed or other external processes to do simple string operations like stripping extensions and prefixes is inefficient. Instead, use parameter expansions which are part of the shell (no external process means it will be faster). Some helpful articles on the subject are listed below:
Bash FAQ 73: Parameter expansions Bash FAQ 100: String manipulations

# Modify timestamp of a file or directory - (YYMMDDhhmm)
touch -t 0712250000 file1

# Create directories `dir1` and `dir2` (in same parent dir)
mkdir dir1 dir2

# Try to create a directory tree
mkdir -p /tmp/dir1/subdir1

# Extract music from m3u (ignore lines start with #, whitespace or are empty)
# Playlists entries could be relative
cd "/path/to/playlists"
cat "playlist1.m3u" "playlist1.m3u" "playlist3.m3u" | grep "^[^# \t]" | tr -s '\n' | while read -r line; do cp --parent -v "$line" /destination; done

# Get extensions of all files
find . -type f -printf "%f\n" | grep -o -E '(\.[^\.]*)$' | sort | uniq

# File checksum SHA256, used in chef cookbooks
openssl dgst -sha256 path/to/myfile
# File checksumMD5
openssl dgst -md5 path/to/myfile
# Read or write BSD-style checksum file
# https://unix.stackexchange.com/a/476480/60668
sha256sum -c SHA256SUMS path/to/myfile
sha256sum --tag path/to/myfile

# Encrypt a file with GNU Privacy Guard
gpg -c file1
# Decrypt a file with GNU Privacy Guard
gpg file1.gpg

# Create hardlink aka hardware link
# Note: It's not possible to create hardlink with a directory (due to the risk of loops in tree)
ln /path/to/source_file /path/to/target_file
ln -T /etc/apache2/sites-available/example.com /etc/apache2/sites-enabled/example.com

# Remove file link
unlink /etc/apache2/sites-enabled/websiteA.exemple

# Create a symbolic link to file or directory
ln -s file1 lnk1

File listing and searching

Find support shell pattern for -path and -ipath parameters:

*/file.ext
*.ext
*/file.*
"always run -type after -name in find commands, since calls to stat to get the type are expensive"
bash - How do I make find fail if -exec fails? - Ask Different

# Find all files that have been modified in the past 7 days
find . -type f -mtime -7

# Search binary files are not used in the last 100 days
find /usr/bin -type f -atime +100

# Find all JPEGs that have been modified more than 30 days ago
find . -name \*.jpg -mtime +30

# Move all JPEGs from the current folder (recursively) that are greater than 40k into the folder /tmp/2
find . -name \*.jpg -size +40k -exec mv {} /tmp/2 +

# search files and directories belonging to `user1`
find / -user user1

# List files by date. See also newest and find_mm_yyyy
ls -lrt

# Print in 9 columns to width of terminal
ls /usr/bin | pr -T9 -W$COLUMNS

# Search 'expr' in this dir and below. See also findrepo
find -name '*.[ch]' | xargs grep -E 'expr'

# Search all regular files for 'example' in this dir and below
find -type f -print0 | xargs -r0 grep -F 'example'

# Search all regular files for 'example' in this dir
find -maxdepth 1 -type f | xargs grep -F 'example'

# Process each item with multiple commands (in while loop)
find -maxdepth 1 -type d | while read dir; do echo $dir; echo cmd2; done

# Get filename (without the extension)
find ./ -name "tile_*.png" -exec bash -c 'filename="$1";echo "${filename%.*}"' _ {} \;

# search files with `.bin` extension within directory `/home/user1`
find /home/user1 -name \*.bin

# Search files with `.rpm` extension and modify permits
find / -name *.rpm -exec chmod 755 '{}' \;

# Search files with `.rpm` extension ignoring removable partitions as cdrom, pen-drive, etc.…
find / -xdev -name \*.rpm

# Find files with the `.ps` extension - first run `updatedb` command
locate \*.ps

#Search cached index for names. This re is like glob *file*.txt
locate -r 'file[^/]*\.txt'

# Find files not readable by all (useful for web site)
find -type f ! -perm -444

# Find dirs not accessible by all (useful for web site)
find -type d ! -perm -111

# Search for empty files and folder (or file with only whitespaces)
find -empty

# List all folders and files, ordered by size
du -ak . | sort -nr | less

# List top 10 largest files and directories
du -a /var | sort -n -r | head -n 10

# Quickly search (sorted) dictionary for prefix
look reference

# Append to each files
find -type f -exec sh -c 'echo "something" >> "$1"' _ {} \;
find -type f -print0 | while IFS= read -r -d '' file; do echo "something" >> "$file"; done
find -type f -exec bash -c 'for file; do echo "something" >> "$file"; done' _ {} \+

# See also https://serverfault.com/questions/343705/how-do-i-append-a-specific-number-of-null-bytes-to-a-file/

bash - Find and replace filename recursively in a directory - Stack Overflow

# Use a simple shell loop, to process each of the images.
mkdir thumbnails
for f in *.jpg
do convert $f -thumbnail 200x90 thumbnails/$f.gif
done

# Use find to substitute filenames into a 'convert' command.
# This also provides the ability to recurse though directories by removing
# the -prune option, as well as doing other file checks (like image type,
# or the disk space used by an image).
find * -prune -name '*.jpg' \
	-exec  convert '{}' -thumbnail 200x90 thumbnails/'{}'.gif \;

# Use xargs -- with a shell wrapper to put the argument into a variable
# This can be combined with either "find" or "ls" to list filenames.
ls *.jpg | xargs -n1 sh -c 'convert $0 -thumbnail 200x90 thumbnails/$0.gif'

# An alternative method on Linux (rather than plain Unix)
# This does not need a shell to handle the argument.
ls *.jpg | xargs -r -I FILE convert FILE -thumbnail 200x90 FILE_thumb.gif

command line - How to find all empty files and folders in a specific directory including files which just look empty but are not? - Ask Ubuntu
unix - Appending new lines to multiple files - Super User - How to use echo "test" >> {} within find exec

Find missing files

How do I find which files are missing from a list? - Unix & Linux Stack Exchange

Find duplicates files

find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate | awk '{$1=""; print substr($0,2)}'

Remove duplicates

#!/bin/bash
gawk '
  {
    cmd="md5 -r " q FILENAME q
    cmd | getline cksm
    close(cmd)
    sub(/ .*$/,"",cksm)
    if(a[cksm]++){
      cmd="rm " q FILENAME q
      system(cmd)
      close(cmd)
    }
    nextfile
  }' q='"' *

bash - How to remove duplicated files in a directory? - Super User

Rdfind – redundant data find:

rdfind -makehardlinks true

fdupes

find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate

BTRFS Deduplication - btrf Wiki

See also diff -q --binary or cmp -s $1 $2 && echo "identical" || echo "different"

Comparing and Merging Files
centos - What's the quickest way to find duplicated files? - Unix & Linux Stack Exchange
```
find -not -empty -type f -printf "%s\n" | sort -rn | uniq -d | xargs -I{} -n1 find -type f -size {}c -print0 | xargs -0 md5sum | sort | uniq -w32 --all-repeated=separate
```
Replace the use of md5sum with diff or cmp: How do I do a binary diff on two identically sized files under Linux? - Super User
dupe-krill/README.md at master · kornelski/dupe-krill
idealo/imagededup: 😎 Finding duplicate images made easy!
birkenfeld/fddf: Fast data dupe finder
haibison / scan4df — Bitbucket

Then replace files by hardlink

Find files by content

# Find multiple exec a executed only if the previous one exit with 0 https://stackoverflow.com/questions/5119946/find-exec-with-multiple-commands#comment34296391_6043896
find -type f -iname "*.properties" -exec grep -q -i -E '^abtest=false$' {} \; -print
find -type f -iname "*.properties" -exec grep -q -i -E '^abtest=' {} \; -exec sed -i 's/^abtest=.*/abtest=true/i' {} \; -print

# Use test to inverse the grep exit value https://stackoverflow.com/a/30495279/470117 (-v/--invert-match option is not useful for that case), for that we need also sh interpreter to use builtin test command
# For append mode (redirection), need to use sh interpreter directly, else {} will be interpreted directly by Bash. See https://superuser.com/questions/1327969/appending-new-lines-to-multiple-files/1327980#1327980
# -exec sh -c 'echo "command name: $0, first arg: $1"' test {} \;
find -iname "*.properties" -exec sh -c 'grep -q -i -E "^abtest=" $1; test $? -eq 1' match {} \; -exec sh -c 'echo -e "\n\nabtest=true" >> $1' append {} \; -print

find -iname "*.properties" -type f -print0 | xargs -0 grep -EHi '^abtest='
# Same as (flexibity of find vs glob include/exclude filters):
grep -EHir --include="*.properties" '^abtest=' /path/to/dir
grep -ir  --include=\*.{php,js,css} "/api/v1/"

# Example search in all .less files that contains `url("<url>")` or `url('<url>')` or `url(<url>)`
find "$wd" -iname "*.less" \( -not -ipath "*/node_modules/*" \) -type f -print0 | xargs -0 grep -EliZ 'url\(('"'"'|"|)(.*?)\1\)' | xargs -0 -n1 echo "Do something with that file:"

find -exec vs find | xargs

Find corrupted files

Find files with 100 consecutive zero bytes (partially downloaded, etc.)

find . -type f -exec egrep "\x00{100,}" {} \; -exec echo {} \;
# If not work try with grep -P

Note: If you get grep: invalid repetition count(s), use (\x00\x00\x00\x00){250,} instead of \x00{1000,} (because repetition as limitation)

linux - How to grep for special character NUL (^@^@^@) - Super User

Delete files and directories

Aka remove files and dirs

# Remove `file1` and `file2`
rm -f file1 file2

# Remove `dir1` and `dir2` and their contents recursively
rm -rf dir1 dir2

# Remove directory `dir1`
rmdir dir1

# Remove all files start with "title_" and ends with ".png"
find . -name 'tile_*.png' -delete
# Remove all files with exceptions:
find . -type f -not \( -name '*.php' -or -name '*.iso' \) -exec rm {} \;
# Remove all files with a list of exceptions:
find . -type f -printf "%P\n" ! -name "list.txt" | fgrep -vf list.txt | xargs -r rm

# Remove empty dir
find <path> -type d -empty -delete
# Can also use (not recommanded)
find <path> -type d -empty -print0 | xargs -0 -I{} rmdir "{}"
find <path> -type d -print0 | xargs -0 -r rmdir -p --ignore-fail-on-non-empty
# Handle trailing dot rmdir error: rmdir -p "./test" -> rmdir: failed to remove directory '.': Invalid argument
find -mindepth 1 -type d -printf '%P\0' | xargs -0 -r rmdir -p --ignore-fail-on-non-empty
# Find all dirs in reverse order (depth first), remove empty dir to top
find -mindepth 1 -type d -print0 | tac -s $'\0' | xargs -0 -r rmdir --ignore-fail-on-non-empty

# Delete all Unix hidden files
# All files or folders that start with `.`, like `.htaccess` or `.DS_STORE`
rm -rf .[^.]*
# All dir `.git`
find . -name ".git" -type d -prune -exec rm -rf {} +
# All dir `node_modules` (which can recusively contains `node_modules` dirs; Use `-prune` for that)
find . -name "node_modules" -type d -prune -exec rm -rf {} +

http://www.cyberciti.biz/faq/linux-bash-delete-all-files-in-directory-except-few/
unix - BASH: How to remove all files except those named in a manifest? - Stack Overflow
linux - find files not in a list - Stack Overflow
Unix tip: Recursively removing empty directories | Network World

Copy or move files and directories

Aka duplicate and rename

# Rename (move) a file or directory
mv dir1 new_dir

# Change file extension
for j in /path/dir/*.html
do
	n=${j/.html}
	mv "$j" "$n.php"
done

# Change file extension
for f in *; do mv "$f" "$f.bin"; done;

# Rename `Ref_00001.jpg` to `anim001.jpg`
find . -name 'Ref_00*.jpg' -print0 | awk 'BEGIN {RS = "\0"; ORS = "\0"} {print; gsub(/\/Ref_00/,"/anim"); print }' | xargs -0 -n2 mv
# Or use bash+sed directly, but less performant
for i in 'Ref_00'*.jpg; do mv "$i" "$(echo $i | sed 's/^Ref_00/anim/')"; done;
# To test, replace find by: `echo -en "Ref_00001.jpg\0Ref_00002.jpg\0Ref_00002.jpg"` and replace xargs with `xargs -0 -n2 echo`

# Rename `sprite1.png` to `sprite0.png`, `sprite2.png` to `sprite1.png`, etc.
find . -maxdepth 1 -type f -exec mv "{}" "{}.tmp" \; -print0 | awk 'BEGIN {RS = "\0"; ORS = "\0"} {match($0,/^(.*sprite)([0-9]+)(.*)$/,a); print a[1]a[2]a[3]".tmp"; print a[1]a[2]-1a[3] }' | xargs -0 -n2 mv
# To test, replace find by: `echo -en "sprite1.png\0sprite2.png\0sprite3.png"` and replace xargs with `xargs -0 -n2 echo`

# Use Perl rename (util-linux rename.ul, perl prename, p5-file-rename)
# Rename *.JPG to *.jpg
rename 's/\.JPG/\.jpg/' *.JPG
# Strip spaces
rename 's/ //' *.jpg
# Lower case
rename 'y/A-Z/a-z/' *

# Copying a file
cp file1 file2
# Copy all files in dir1 to dir2 (recursively)
cp -R dir1/. dir2/
# Copy all files of a directory within the current work directory
cp dir/* .
# Copy a directory within the current work directory
cp -a /tmp/dir1 .
# Copy a directory
cp -a dir1 dir2

# Find and copy all files with `.txt` extension from a directory to another
find /home/user1 -name '*.txt' | xargs cp -av --target-directory=/home/backup/ --parents

# local copy preserving permissions and links from a directory to another
tar cf - . | (cd /tmp/backup ; tar xf - )

On macOS install it with port port install p5-file-rename (but should use the cmd rename-5.22 where 22 is installed version via port instead of rename) or brew brew install rename

unix - How to do a mass rename? - Stack Overflow

Archives and compressed files

# Decompress a file called `file1.bz2`
bunzip2 file1.bz2

# Compress a file called `file1`
bzip2 file1

# Decompress a file called `file1.gz`
gunzip file1.gz

# Compress a file called `file1`
gzip file1

# Compress with maximum compression
gzip -9 file1

# Create an archive rar called `file1.rar`
rar a file1.rar test_file

# Compress `file1`, `file2` and `dir1` simultaneously
rar a file1.rar file1 file2 dir1

# Decompress rar archive
rar x file1.rar

# Create a uncompressed tarball
tar -cvf archive.tar file1

# Create an archive containing `file1`, `file2` and `dir1`
tar -cvf archive.tar file1 file2 dir1

# Show contents of an archive
tar -tf archive.tar

# Extract a tarball
tar -xvf archive.tar
# Extract a tarball into / tmp
tar -xvf archive.tar -C /tmp

# Create a tarball compressed into bzip2
tar -cvfj archive.tar.bz2 dir1
# Create a tarball compressed into gzip
tar -cvfz archive.tar.gz dir1

# Decompress a compressed tar archive in bzip2
tar -xvfj archive.tar.bz2
# Decompress a compressed tar archive in gzip
tar -xvfz archive.tar.gz

# Make a incremental backup of directory `/home/user`
tar -Puf backup.tar /home/user

# Decompress rar archive
unrar x file1.rar

# Decompress a zip archive
unzip file1.zip

# Create an archive compressed in zip
zip file1.zip file1

# Compress in zip several files and directories simultaneously
zip -r file1.zip file1 file2 dir1

Create archive from file list:

#!/bin/bash
# Create temp list
list=$(mktemp "/tmp/archive_list.XXXXXXXXXX")
# Write stdin file / folder list
cat > "$list"
# Get destination folder based on first file / folder
first=$(head -n 1 "$list")
folder=$(dirname "$first")
# Temporary file and final file
final="$folder/Archive.zip"
file="$final.tmp"
# Create archive file (zip, ultra)
/opt/local/bin/7z a -tzip -mx=9 "$file" @"$list"
# Move to final destination
mv "$file" "$final"
# Remove temp list
rm "$list"

Split files

FAT32 maximum file size is "4 GiB minus 1 byte" (4294967295 bytes)

To write file with a size larger than that limit, you need to split it.

In destination folder, execute following command:

split -b 4294967295 example.dmg example.dmg.part.

(the part example.dmg.part. will be used to name output files like example.dmg.part.aa, example.dmg.part.ab and so on)

cat example.dmg.part.* > example.dmg

Read write race condition

cat tmp | head -1 >new && mv new tmp
{ cat tmp | head -1; } >tmp

bash - How to make reading and writing the same file in the same pipeline always "fail"? - Unix & Linux Stack Exchange

Choose incremental filename

Test if dirB/file.ext exist else choose dest file name as dirB/file-1.ext, if already exist choose dirB/file-2.ext and so one

source=dirA/file.ext
dest_dir=dirB

file=$(basename file.ext)
basename=${file%.*}
ext=${file##*.}

if [[ ! -e "$dest_dir/$basename.$ext" ]]; then
	# file does not exist in the destination directory
	mv "$source" "$dest_dir"
else
	num=2
	while [[ -e "$dest_dir/$basename-$num.$ext" ]]; do
		(( num++ ))
	done
	mv "$source" "$dest_dir/$basename-$num.$ext"
fi

File attributes

# Allows write opening of a file only append mode
chattr +a file1
# Allows that a file is compressed / decompressed automatically by the kernel
chattr +c file1
# Makes it an immutable file, which can not be removed, altered, renamed or linked
chattr +i file1
# All attributes (see details in the manpage of `chattr`):
# - append only (a)
# - compressed (c)
# - no dump (d)
# - extent format (e)
# - immutable (i)
# - data journalling (j)
# - secure deletion (s)
# - no tail-merging  (t)
# - undeletable  (u)
# - no atime updates (A)
# - synchronous directory updates (D)
# - synchronous updates (S)
# - top of directory hierarchy (T)

# show specials attributes
lsattr

File type

# Get file type if known by libmagic
file --mime /path/file

# Get information about files in the current folder
find . -maxdepth 1 -type f -exec file "{}" \;

Supported formats are listed by:

files in /etc/magic
/etc/magic.mime
/usr/share/misc/magic.mgc
/usr/share/file/magic.mgc
/opt/local/share/misc/magic.mgc
files in /opt/local/share/misc/magic
~/.magic.mgc
~/.magic

The extension of compiled magic: *.mgc

# Test if a file exist
filename=$1
if [ -f $filename ]
then
	echo "$filename exists"
else
	echo "$filename does NOT exist"
fi

Files permissions

# Change group of files
chgrp group1 file1

# Set permissions reading (r), write (w) and (x) access to users owner (u) group (g) and others (o)
chmod ugo+rwx directory1
# Remove permits reading (r), write (w) and (x) access to users group (g) and others (or
chmod go-rwx directory1
# Set SUID bit on a binary file - the user that running that file gets same privileges as owner
chmod u+s /bin/file1
# Disable SUID bit on a binary file
chmod u-s /bin/file1
# Set SGID bit on a directory - similar to SUID but for directory
chmod g+s /home/public
# Disable SGID bit on a directory
chmod g-s /home/public

# Set STIKY bit on a directory - allows files deletion only to legitimate owners
chmod o+t /home/public
# Disable STIKY bit on a directory
chmod o-t /home/public

# Change owner of a file
chown user1 file1
# Change user owner of a directory and all the files and directories contained inside
chown -R user1 directory1
# Change user and group ownership of a file
chown user1:group1 file1

# View all files on the system with SUID configured
find / -perm -u+s

Name, extension and parent folder

Note: Don't use parameter substitution, it's not work with all cases

folder=/tmp
dirname "$folder"
# /
basename "$folder"
# tmp
echo "${folder%/*}"
#
echo "${folder%/*.*}"
# /tmp
echo "${folder##*/}"
# tmp
echo "${folder##*.}"
# /tmp

folder2=/tmp/folder
dirname "$folder2"
# /tmp
basename "$folder2"
# folder
echo "${folder2%/*}"
# /tmp
echo "${folder2%/*.*}"
# /tmp/folder
echo "${folder2##*/}"
# folder
echo "${folder2##*.}"
# /tmp/folder

file=/tmp/file.png
dirname "$file"
# /tmp
basename "$file"
# file.png
echo "${file%/*}"
# /tmp
echo "${file%/*.*}"
# /tmp
echo "${file##*/}"
# file.png
echo "${file##*.}"
# png

extension=$([[ "$file" = *.* ]] && echo "${file##*.}" || echo '')

Read file content or stream

# View the contents of a file starting from the first row
cat file1

# View first two lines of a file
head -2 file1

# Pagers (moving down the file content one screen at a time)
# View content of a file along, allowing only forward navigation through the file
more file1
# View content of a file along, allowing forward and backward navigation through the file
less file1

# View the contents of a file starting from the last line
tac file1

# View last two lines of a file
tail -2 file1
# View in real time what is added to a file
tail -f /var/log/messages

# View from line 20 to 30 of a file
sed -n '20,30 p' file1
# View from line 20 to end of a file
sed -n '20,$ p' file1
# View from the begining to line 20 of a file
sed -n '1,20 p' file1

# Divide into 5 columns
ls /tmp | pr -T5 -W$COLUMNS

Terminal pager - Wikipedia

Create or truncate a file

# Create or tuncate a file
> /var/log/apache2/error.log
# Create an empty file or change the modification date
touch file.ext

# Create a large test file (taking no space)
dd bs=1 seek=2TB if=/dev/null of=file.ext

File comparaisons

Note: you can export LANG=C for speed. Also these assume no duplicate lines within a file

# Union of unsorted files
sort file1 file2 | uniq
# Intersection of unsorted files
sort file1 file2 | uniq -d
# Difference of unsorted files
sort file1 file1 file2 | uniq -u
# Symmetric Difference of unsorted files
sort file1 file2 | uniq -u

# Union of sorted files
join -t'\0' -a1 -a2 file1 file2
# Intersection of sorted files
join -t'\0' file1 file2
# Difference of sorted files
join -t'\0' -v2 file1 file2
# Symmetric Difference of sorted files
join -t'\0' -v1 -v2 file1 file2

Use diff and patch

Compare 2 folders:

Sans -q mais avec -u pour faire un patch

diff -rq /path/dirA /path/dirB

Et sans prendre en compte les fichiers metadonnées d'OSX et de Windows, le tout ordonné :

diff -uqr /path/dirA /path/dirB | grep -v -e 'DS_Store' -e 'Thumbs' | sort

Comparer 2 files:

diff -u /path/fileA /path/fileB

The Ten Minute Guide to diff and patch

Apply a patch:

patch -i my.patch

Use heredoc

patch -i -p1 - <<EOF
diff -ur a/Makefile.in b/Makefile.in
--- a/Makefile.in	2016-03-13 01:08:14.000000000 +0100
+++ b/Makefile.in	2016-03-13 01:09:13.000000000 +0100
@@ -1,3 +1,4 @@
+vpath = src
 top_builddir = ..
 srcdir = @srcdir@
 top_srcdir = @top_srcdir@
EOF

Use -p1 to strip path a/ and b/

Folder bind

Aka folder link, like symlink but for folder (standart implementation don't allow to link folder)

# Mount a folder at a specific point (here `/path/destdir`)
mount --bind /path/srcdir /path/destdir
# Unmount
umount /path/destdir

The mount point is registerd in /etc/fstab as fs-type: bind

Archives and compression

# Encrypt file
gpg -c file

# Decrypt file
gpg file.gpg

# Make compressed archive of dir/
tar -c dir/ | bzip2 > dir.tar.bz2
# Find all files with `.log` extension and make an bzip archive
find /var/log -name '*.log' | tar cv --files-from=- | bzip2 > log.tar.bz2

# Extract archive (use gzip instead of bzip2 for tar.gz files)
bzip2 -dc dir.tar.bz2 | tar -x

# Make encrypted archive of dir/ on remote machine
tar -c dir/ | gzip | gpg -c | ssh user@remote 'dd of=dir.tar.gz.gpg'

# Make archive of subset of dir/ and below
find dir/ -name '*.txt' | tar -c --files-from=- | bzip2 > dir_txt.tar.bz2

# Make copy of subset of dir/ and below
find dir/ -name '*.txt' | xargs cp -a --target-directory=dir_txt/ --parents

# Copy (with permissions) copy/ dir to /where/to/ dir
( tar -c /dir/to/copy ) | ( cd /where/to/ && tar -x -p )

# Copy (with permissions) contents of copy/ dir to /where/to/
( cd /dir/to/copy && tar -c . ) | ( cd /where/to/ && tar -x -p )

# Copy (with permissions) copy/ dir to remote:/where/to/ dir
( tar -c /dir/to/copy ) | ssh -C user@remote 'cd /where/to/ && tar -x -p'

# Backup harddrive (raw) to remote machine
dd bs=1M if=/dev/sda | gzip | ssh user@remote 'dd of=sda.gz'

Incremental listing

Incrementaly add/changed/delete files (list made from cron or similar)

find . -type f -mtime -7 -exec ls -l {} \; > list.txt
find . -type f -exec ls -i {} + | sort -k2 > list.txt
tar --create --file=archive.1.tar --listed-incremental=/var/log/usr.snar .
tar -cf /dev/null -g /var/log/usr.snar .
date +%s

/backupdevice/folder
date +%s%N > /backupdevice/folder.index

Change encoding

Use recode that obsoletes iconv, dos2unix, unix2dos

# Show available conversions (aliases on each line)
recode -l
#iconv -l

# Windows "ansi" to local charset (auto does CRLF conversion)
recode windows-1252.. file_to_change.txt

# Windows utf8 to local charset
recode utf-8/CRLF.. file_to_change.txt

# Latin9 (western europe) to utf8
recode iso-8859-15..utf8 file_to_change.txt
#iconv -f iso-8859-15 -t utf-8 <infile> -o <outfile>

# Base64 encode / decode
recode ../b64 < file.png

# Quoted printable decode
recode /qp.. < file.qp > file.txt

# Text to HTML
recode ..HTML < file.txt > file.html

# Lookup table of characters
recode -lf windows-1252 | grep euro

# Convert a text file format from MSDOS to UNIX (line-ending CRLF to LF)
recode ibmpc..latin1 file file2
#dos2unix file file2
#cat file | tr -d '\r' > file2 && mv -v file2 file
#sed -i s/\r//g file

# convert a text file format from UNIX to MSDOS (line-ending LF to CRLF)
recode latin1..ibmpc file file2
#unix2dos file file2
#sed -i 's/$/\r/' file

# Show what a code represents in latin-9 charmap
echo -n 0x80 | recode latin-9/x1..dump

# Show latin-9 encoding
echo -n 0x20AC | recode ucs-2/x2..latin-9/x

# Show utf-8 encoding
echo -n 0x20AC | recode ucs-2/x2..utf-8/x

Temporary file

temp_file=$(mktemp)
# Remove the file when the script exit
trap "rm -f $temp_file" 0

# do something with the file
echo "Hello World!" > $temp_file
cat $temp_file
# Remove the file now (optional)
rm -f "$temp_file"

# Do something else

tmp - How create a temporary file in shell script? - Unix & Linux Stack Exchange - See example with file descriptor, which is cleaned automatically
Mktemp with suffix/extension | Gawen's blog - Use temp dir instead of temp file

Prefix a list of paths

If sed pattern come from variable, some escaping is needed: sed "s/$BRE/$REPL/"

Instead use awk with variables:

prefix=/some/path/to/
# awk sub() can be use to replace with regex
find -printf '%P\0' | awk -v prefix="$prefix" 'BEGIN {RS = "\0"; ORS = "\0"} {print prefix $0}' | do_something_with_null_sep_list

Change file in-place

file=test.json
tmp=$(mktemp -u "${file}.XXXXXXXXXX")
address=abcde
jq --arg a "$address" '.address = $a' "$file" > "$tmp" && mv "$tmp" "$file"

contents="$(jq '.address = "abcde"' test.json)" && echo -E "${contents}" > test.json
# Note "contents" cannot contain a literal null character. Bash variables cannot store literal nulls.

Or sponge

Do not use echo "$( jq '.address = "abcde"' test.json )" > test.json, this will not always work. Large files it will cause issues, also with whitespaces, non-printable and escapment sequences. Never redirect a file to itself, it is always a bad idea.

Relative path

function relative_path_from_to() {
    # strip trailing slashes
    path1=${1%\/}
    path2=${2%\/}
    # common part of both paths
    common=$(printf '%s\x0%s' "${path1}" "${path2}" | sed 's/\(.*\/\).*\x0\1.*/\1/')
    # how many directories we have to go up to the common part
    up=$(grep -o "/" <<< ${path1#$common} | wc -l)
    # create a prefix in the form of ../../ ...
    prefix=""; for ((i=0; i<=$up; i++)); do prefix="$prefix../"; done
    # return prefix plus second path without common
    printf "$prefix${2#$common}"
}

relative_path_from_to /path/test1/file /path/test2/file
# > ../../test2/file

# require the path of both file and dir to exist, resolve symlink
realpath --relative-to=DIR FILE

Text operations

Aka text processing

# Echo multiline string (use the newline separator `\n`)
echo -e "a\nb"

# Add line to begin of file, aka prepend text
echo "firstline" | cat - file.txt > file.txt.tmp && mv file.txt.tmp file.txt

# Convert from lower case in upper case
tr '[:lower:]' '[:upper:]'

# Sort contents of two files
sort file1 file2
# Sort contents of two files omitting lines repeated
sort file1 file2 | uniq
# Sort contents of two files by viewing only unique line
sort file1 file2 | uniq -u
# Sort contents of two files by viewing only duplicate line
sort file1 file2 | uniq -d

# Sort IPV4 ip addresses
sort -t. -k1,1n -k2,2n -k3,3n -k4,4n

# Filter non printable characters
tr -dc '[:print:]'

# cut fields separated by blanks
tr -s '[:blank:]' '\t'

# Count lines
wc -l

# Number row of a file
cat -n file1

# Compare contents of two files by deleting only unique lines from `file1`
comm -1 file1 file2
# Compare contents of two files by deleting only unique lines from `file2`
comm -2 file1 file2
# Compare contents of two files by deleting only the lines that appear on both files
comm -3 file1 file2
# Compare with awk: https://stackoverflow.com/questions/15065818/compare-files-with-awk

# Find differences between two files
diff file1 file2

# Look up words "Aug" on file `/var/log/messages`
grep Aug /var/log/messages

# Look up words that begin with "Aug" on file `/var/log/messages`
grep ^Aug /var/log/messages

# Select from file `/var/log/messages` all lines that contain numbers
grep [0-9] /var/log/messages

# Search string "Aug" at directory `/var/log` and below
grep Aug -R /var/log/*

# Find text in files
grep -rn "texttofind" *
grep "string text to find in all files" . -R

# Highlight occurances of regular expression in dictionary
grep --color reference /usr/share/dict/words

# Merging contents of two files for columns
paste file1 file2

# Merging contents of two files for columns with `+` delimiter on the center
paste -d '+' file1 file2

# Find differences between two files and merge interactively alike `diff`
sdiff file1 file2

# Find in files with a multile regex
# See https://stackoverflow.com/a/7167115/470117
find ./path/to/files -type f -exec grep -Pazo '(?s)<control>.*?</control>' {} \+

# Split string into an array
mapfile -d '' array < <(echo -en "a\0b\0c")

# Join array with single char separator
echo "$(IFS=, ; echo "${array[*]}")"
# Join array with multi chars separator
printf "\"%s\"," "${array[@]}"

How can I join elements of a Bash array into a delimited string? - Stack Overflow

Sed

Aka stream editor

Note: sed uses stdin and stdout. Newer versions support inplace editing with the -i option

Remove multiline comment:

# Remove in place all multiline comments
# Note: see also m regex flag
sed -Ei -e '1h;2,$H;$!d;g' -e 's|/\*.*?\*/||g' file.ext
# Single line only (sed match by default on line basis)
sed -i '/<!--.*-->/ d' file
# Note: the , implied the multiple lines.
sed -i '/<!--/,/-->/ d' file

AWK

AWK reads the input a line at a time. A line is scanned for each pattern in the program, and for each pattern that matches, the associated action is executed.

# Print all fields
awk '{print NR": "$0; for(i=1;i<=NF;++i) print "\t"i": "$i}'

# Remove all even lines
awk 'NR%2==1'

# View the first column of a line
echo a b c | awk '{print $1}'

# View the first and third column of a line
echo a b c | awk '{print $1,$3}'

#!/usr/bin/env awk -f

{print $0}

Disk and file system operations

# Mounting a Filesystem:
# force umount when the device is busy
fuser -km /mnt/hda2
# mount disk called hda2 - verify existence of the directory `/mnt/hda2`
mount /dev/hda2 /mnt/hda2
# mount a floppy disk
mount /dev/fd0 /mnt/floppy
# mount a cdrom / dvdrom
mount /dev/cdrom /mnt/cdrom
# mount a cdrw / dvdrom
mount /dev/hdc /mnt/cdrecorder
# mount a cdrw / dvdrom
mount /dev/hdb /mnt/cdrecorder
# mount a file or iso image
mount -o loop file.iso /mnt/cdrom
# mount a Windows FAT32 file system
mount -t vfat /dev/hda5 /mnt/hda5
# mount a usb pen-drive or flash-drive
mount /dev/sda1 /mnt/usbdisk
# mount a windows network share
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share
# unmount disk called hda2 - exit from mount point `/mnt/hda2` first
umount /dev/hda2
# run umount without writing the file /etc/mtab - useful when the file is read-only or the hard disk is full
umount -n /mnt/hda2

# Show all partitions registered on the system
cat /proc/partitions
# List mounted filesystems on the system (and align output)
mount | column -t

# Show info about disk sda
hdparm -i /dev/sda
# displays the characteristics of a hard-disk
hdparm -i /dev/hda
# perform test reading on a hard-disk
hdparm -tT /dev/sda

# Do a read speed test on disk sda
hdparm -tT /dev/sda
# Test for unreadable blocks on disk sda
badblocks -s /dev/sda
# How long has this disk (system) been powered on in total
smartctl -A /dev/sda | grep Power_On_Hours

# Check bad blocks on disk hda1
badblocks -v /dev/hda1

# Repair / check integrity of dos filesystems on disk hda1
dosfsck /dev/hda1

# Repair / check integrity of ext2 filesystem on disk hda1
e2fsck /dev/hda1
# Repair / check integrity of ext3 filesystem on disk hda1
e2fsck -j /dev/hda1

# Repair / check integrity of linux filesystem on disk hda1
fsck /dev/hda1

# Repair / check integrity of ext2 filesystem on disk hda1
fsck.ext2 /dev/hda1
# Repair / check integrity of ext3 filesystem on disk hda1
fsck.ext3 /dev/hda1
# Repair / check integrity of fat filesystem on disk hda1
fsck.vfat /dev/hda1
# Repair / check integrity of dos filesystem on disk hda1
fsck.msdos /dev/hda1

Backup the filesystem

# Note: only supported by ext2/ext3 filesystems
# Make a full backup of directory `/home`
dump -0aj -f /tmp/home0.bak /home
# Make a incremental backup of directory `/home`
dump -1aj -f /tmp/home0.bak /home
# Restoring a backup interactively
restore -if /tmp/home0.bak

Format a filesystem:

# Format a floppy disk
fdformat -n /dev/fd0

# Create a filesystem type linux ext2 on hda1 partition
mke2fs /dev/hda1
# Create a filesystem type linux ext3 (journal) on hda1 partition
mke2fs -j /dev/hda1

# Create a filesystem type linux on hda1 partition
mkfs /dev/hda1
# Create a FAT32 filesystem
mkfs -t vfat 32 -F /dev/hda1

Filesystem swap:

# Create a swap filesystem
mkswap /dev/hda3

# Activating a new swap partition
swapon /dev/hda3

# Activate two swap partitions
swapon /dev/hda2 /dev/hdb3

Disk space

Clone disk

# Make a copy of a local hard disk on remote host via ssh
dd bs=1M if=/dev/hda | gzip | ssh user@ip_addr 'dd of=hda.gz'

# Copy content of the harddrive to a file
dd if=/dev/sda of=/tmp/file1

# Make a copy of MBR (Master Boot Record) to floppy
dd if=/dev/hda of=/dev/fd0 bs=512 count=1

# Restore MBR from a copy saved to floppy
dd if=/dev/fd0 of=/dev/hda bs=512 count=1

Aka duplicate disks

For supported partitions (on source drive), use Disk Utility

For not supported partitions

Clone exact disk (boot sector, all partitions & data, etc.) to an other drive (to a file, use a path to a file instead of /dev/sdX, see this page for other options like split the image and dd man page for partial copy etc.)

For disk use /dev/sdX (or /dev/hdX, or BSD /dev/diskX or even /dev/rdiskX for better speed)

# From sdX to sdY
sudo dd if=/dev/sdX of=/dev/sdY bs=64K conv=noerror,sync status=progress

Change bs to find the optimal value. 64K seem a good value, but it's related to hardware and software (USB2.0 to USB2.0 RAID). Try to use the same value as the disk cache 8388608 size, or the block size 4096.

With bs=64K:

USB 2.0 to USB 2.0: 20 to 11 MB/s
SATA 3.0 (3.0 Gb/s) to SATA 3.0 (3.0 Gb/s): 130 MB/s

# In the following example, we work with 4th disk (/dev/sdd), which have 3 partition (1: /dev/sdd1, 2: /dev/sdd2, 5: /dev/sdd5) which is part of a RAID  Synology Hybrid RAID (SHR) with only one disk
# Disk 1: /dev/sda, disk 2: /dev/sdb, etc. SATA: /dev/sdg

# Duplicate the disk on SATA disk
sudo dd if=/dev/sdd of=/dev/sdg bs=64K status=progress
# Could lead to an error "client_loop: send disconnect: Broken pipe", the SSH session stopped copy end. We need to keep the SSH client awake

# Stop the NAS
# Switch disks in the bay: replace disk 4 with the SATA disk
# Start the NAS
# Repair volume in Storage Manager (System Partition Failed): Repair System Partition (see https://kb.synology.com/en-us/DSM/help/DSM/StorageManager/disk)
# Check some infos
sudo smartctl -a /dev/sdd
# Check partitions
sudo sfdisk -l /dev/sdd
# Recreate partition from offset (based on previous command, here partition n°5 /dev/sdd5)
sudo sfdisk -N5 -o9453280 -z-1 -tfd /dev/sdd
# Check partitions
sudo sfdisk -l /dev/sdd
# Check RAID state
cat /proc/mdstat
sudo mdadm -D /dev/md4
# Grow RAID volume
sudo mdadm --grow /dev/md4 --size=max
# Unmount volume, this will trigger bip
sudo umount -f /volume3
# or sudo umount -l /volume3
# Stop the RAID volume
sudo mdadm --stop /dev/md4
# If this return the error "mdadm: Cannot get exclusive access to /dev/md4:Perhaps a running process, mounted filesystem or active volume group?", you need to restart the NAS with the disk 4 out of the bay
# Restart the RAID volume and update it size
sudo mdadm --assemble /dev/md4 /dev/sdd5 --update=devicesize
# Check resize
cat /sys/block/md4/md/dev-sdd5/size
# List logical volumes (LVM)
sudo pvdisplay
# Resize LVM
sudo pvresize /dev/md4
# Restart the NAS
# Extend unused space on volume in Storage Manager

# See also
sudo pvdisplay
sudo vgdisplay
sudo lvdisplay
cat /etc/fstab

CDs

And DVDs, CD images

# Save copy of data cdrom
gzip < /dev/cdrom > cdrom.iso.gz

# Create cdrom image from contents of dir
mkisofs -V LABEL -r dir | gzip > cdrom.iso.gz

# Mount the cdrom image at /mnt/dir (read only)
mount -o loop cdrom.iso /mnt/dir

# Clear a CDRW
cdrecord -v dev=/dev/cdrom blank=fast

# Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)
gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom -

# Rip audio tracks from CD to wav files in current dir
cdparanoia -B

# Make audio CD from all wavs in current dir (see also cdrdao)
cdrecord -v dev=/dev/cdrom -audio -pad *.wav

# perform an md5sum on a device, like a CD
dd if=/dev/hdc | md5sum

# mount an ISO image
mount -o loop cd.iso /mnt/iso

Command operations

# Show full path to a binary / executable
which command
# Show location of a binary file, source or man
whereis command

# See how long a command takes (stopwatch). Ctrl-d to stop. See also sw
time command

# Show commands pertinent to string. See also threadsafe
# Display a list of commands that pertain to keywords of a program, useful when you know what your program does, but you don't know the name of the command
apropos somekeyword

# Find the location of a command
command -v git 2> /dev/null

Command help

Aka man, command documentation

# displays description of what a program does
whatis somekeyword

man mv

# find any related commands
man -k mv

# make a pdf of a manual page
man -t ascii | ps2pdf - > ascii.pdf

Section numbers of the man manual:

executable programs or shell commands
system calls (functions provided by the kernel)
library calls (functions within program libraries)
special files (usually found in /dev)
file formats and conventions eg /etc/passwd
games
miscellaneous (including macro packages and conventions), e.g. man(7), groff(7)
system administration commands (usually only for root)
kernel routines (non standard)

What do the parentheses and number after a Unix command or C function mean? Like: man(8), ftok(2), mount(8)?

Some commands support also (or instead) an option that show the help, could be:

--help
-h
help
-?
/?

SSH

Aka Secure SHell

# Run command on $HOST as $USER (default command=shell)
ssh $USER@$HOST command

# Run GUI command on $HOSTNAME as $USER
ssh -f -Y $USER@$HOSTNAME xeyes

# Copy with permissions to $USER's home directory on $HOST
scp -p -r $USER@$HOST: file dir/

# Use faster crypto for local LAN. This might saturate GigE
scp -c arcfour $USER@$LANHOST: bigfile

# Forward connections to $HOSTNAME:8080 out to $HOST:80
ssh -g -L 8080:localhost:80 root@$HOST

# Forward connections from $HOST:1434 in to imap:143
ssh -R 1434:imap:143 root@$HOST

# Install public key for $USER@$HOST for password-less log in
ssh-copy-id $USER@$HOST

To disallow SSH remote root login, in /etc/ssh/sshd_config update/add:

PermitRootLogin no

moul/quicssh: SSH over QUIC

SSH Keyfile

# If `-f filename` is not defined, will generate 2 files (by default `~/.ssh/id_rsa` and `~/.ssh/id_rsa.pub`)
ssh-keygen -t rsa -b 4096 -f ~/.ssh/user@host_rsa
ssh-keygen -t rsa -b 4096 -C "your_email@example.com" -f ~/.ssh/your_email@example.com_rsa
ssh-keygen -t rsa -b 4096 -C "your_email@example.com" -f ~/.ssh/your_email@example.com-hostname.ext_rsa

In ~/.ssh/config:

# username@hostname
Host hostname
RSAAuthentication yes
IdentityFile ~/.ssh/username@hostname_rsa
User username

Generating a new SSH key and adding it to the ssh-agent - User Documentation
SSH Configurations - Tower Help - Connecting & Authenticating

Convert PDF 1.4

Force version

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4  -dColorConversionStrategy=/LeaveColorUnchanged -dDownsampleMonoImages=false -dDownsampleGrayImages=false -dDownsampleColorImages=false -dAutoFilterColorImages=false -dAutoFilterGrayImages=false -dColorImageFilter=/FlateEncode -dGrayImageFilter=/FlateEncode -o airbus_ar_2016_pdf1.4.pdf airbus_ar_2016.pdf

Email local spool

/var/spool/mail/$USER

mail -s "Hello" localusername </dev/null

UUID

# UUID (but violates the UUID specification)
od -x /dev/urandom | head -1 | awk '{OFS="-"; print $2$3,$4,$5,$6,$7$8$9}'
# UUID v4
od -x /dev/urandom | head -1 | awk '{OFS="-"; srand($6); sub(/./,"4",$5); sub(/./,substr("89ab",rand()*4,1),$6); print $2$3,$4,$5,$6,$7$8$9}'

How to create a UUID in bash? - Server Fault

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Configuration

Conserver la configuration d'iptables lors des démarrages

Gestion des services

User prompt

User management

Network

Windows networking

HTTP

SSH Tunnel

Backup external server

Copy files over SSH

Copy files over SSH shell

Copy files with sftp

Copy files with lftp

Copy files from FTP with wget

Copy files with rsync

Math

Date and clock

Locale

Packages

Monitoring and debugging

System

System information

Power management

Interactive

Shell

Shell config

Command alias

Programmable bash completions

Terminal history auto complete

Shell variables

Colors and control sequences

Mouse position and click

Command arguments

Command alias

Shell script file

Shell script syntax

Redirection

Fork process

Add a bin folder to global executables

Automatic error detection

Dotfiles

Tree navigation

Files and folders operations

File listing and searching

Delete files and directories

Copy or move files and directories

Archives and compressed files

Split files

Read write race condition

Choose incremental filename

File attributes

File type

Files permissions

Name, extension and parent folder

Read file content or stream

Create or truncate a file

File comparaisons

Use diff and patch

Folder bind

Archives and compression

Incremental listing

Change encoding

Temporary file

Prefix a list of paths

Change file in-place

Relative path

Text operations

Sed

AWK

Disk and file system operations

Disk space

Clone disk

CDs

Command operations

Command help

SSH

SSH Keyfile

Convert PDF 1.4

Email local spool

Copy files with `sftp`

Copy files with `lftp`

Copy files from FTP with `wget`

Copy files with `rsync`