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++101 Linux commands Open-source eBook

This is an open-source eBook with 101 Linux commands that everyone should know. No matter if you are a DevOps/SysOps engineer, developer, or just a Linux enthusiast, you will most likely have to use the terminal at some point in your career.

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https://github.com/bobbyiliev/101-linux-commands-ebook/blob/main/ebook/en/export/101-linux-commands-ebook-dark.pdf

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https://github.com/bobbyiliev/101-linux-commands-ebook/blob/main/ebook/en/export/101-linux-commands-ebook-light.pdf

Basics

File Hierarchy Standard (FHS)

Path	Content
`/bin`	Binaries (User)
`/boot`	Static boot loader files
`/etc`	Host specific configs
`/lib`	Shared libraries and kernel modules
`/sbin`	Binaries (System/root)
`/var`	Varying files (e.g. Logs)
`/usr`	3rd party software
`/proc`	Pseudo file system
`/sys`	Pseudo file system
`/mnt`	Mountpoint for internal drives
`/media`	Mountpoint for external drives
`/home`	User homes
`/run`	PID files of running processes

Commands

File System Commands

Command	Options	Description
`cd`	`-`	Navigate to last dir
	`~`	Navigate to home
	`~username`	Navigate to home of specified user
`pwd`		Print working dir
`ls`		Print dir content
	`-l`	Format as list
	`-a`	Show hidden items (`-A` without `.` and `..`)
	`-r`	Invert order
	`-R`	Recurse
	`-S`	Sort by size
	`-t`	Sort by date modified
`mkdir`	`-p`	Create dir with parents
`cp`	`-r`	Copy dir
`rmdir`	`-p`	Remove dir and empty parents
`rm`	`-rf`	Remove dir recursively, `-f` without confirmation
`mv`		Move recursively
`find`	`-iname pattern`	Search dir/file case-insensitive
	`-mmin n`	Last modified n minutes ago
	`-mtime n`	Last modified n days ago
	`-regex pattern`	Path matches pattern
	`-size n[kMG]`	By file size (`-n` less than; `+n` greater than)
	`! searchparams`	Invert search

File Manipulation

Command	Options	Description
`cat`	`file`	Print content
`tac`	`file`	Print content inverted
`sort`	`file`	Print sorted
	`file -r -u`	Print sorted descending without dublicates
`head`	`-n10 file`	Print lines 5-10
`tail`	`-f file`	Print new lines automatically
`cut`	`-f -4,7-10,12,15- file`	Print selected fields (tab delimited)
	`-c -4,7-10,12,15- file`	Print selected characters positions
	`-f 2,4 -d, --output-delimiter=$'\t' file`	Change delimiter (but use tab for output)
`uniq`	`file`	Hide consecutive identical lines
	`file -c`	Show consecutive identical line count
	`file -u`	Hide consecutive identical lines
`file`	`file`	Get file type
`wc`	`file`	Count Lines, Words, Chars (Bytes)

Archiving

Command	Options	Description
`tar`	`cfv archiv.tar file1 file2`	Create archive / add or overwrite content
	`tfv archiv.tar`	Show content
	`xf archiv.tar [-C ~/extracted]`	Extract (and decompress) archive (to ~ / extracted)
	`cfvj archiv.tar.bz2 file`	Create bzip2 compressed archive
	`cfvz archiv.tar.gz file`	Create gzip compressed archive
	`cfa archiv.tar.[komp] file`	create compressed archive (auto type based on name)
`bzip2`	`file1 file2`	Dateien (einzeln) komprimieren
	`-d file1 file2`	Compress files (one at a time)
`gzip`	`file1 file2`	Dateien (einzeln) komprimieren
	`-d file1 file2`	Decompress files

Disk and File System Management

General Disk Manipulation (non-LVM)

Creating physical partitions is not required! You can create PVs directly!

Command	Options	Description
`fdisk`	`-l`	List physical disks and partitions
	`/dev/sdb` `n`	Create new partition
	`/dev/sdb` `t` `8e`	Change partition type to Linux LVM
`mkfs.xfs`	`/dev/myVG/myVol`	Format LV with XFS
`mkfs.ext4`	`-f /dev/myVG/myVol`	Format LV with EXT4 (overwrite)
`blkid`	`/dev/myVG/myVol`	Show UUID and formatting of volume
`mount`		Show current mounted file systems
	`-t ext4 /dev/myVG/myVol /mountpoint`	Mount LV to /mountpoint
	`-a`	Mount as configured in /etc/fstab
`umount`		Unmount a file system
	`/dev/myVG/myVol`	Unmount LV from /mountpoint
	`/mountpoint`	Unmount LV from /mountpoint
`df`	–	Show disk usage
`xfs_growfs`	`/dev/myVG/myVol`	Resize xfs filesystem
`resize2fs`	`/dev/myVG/myVol`	Resize ext3/4 filesystem

Other

Command	Options	Description
`<command>`	`--help`	Help of current command (not standardized)
	`-h`
	`-?`
`man`	`<command>`	Manual page of command
	`-k keyword`	Search command by keyword (oder `apropos`)
`alias`		Show aliases
	`name='befehl'`	Create alias

Globs (Wildcards)

The dot . in front of hidden items is ignored by glob patterns!

Character	Description
`?`	Any single character
`*`	Any characters
`[ac-e]`	1 character in enum
`[!ac-e]`	1 character not in enum

Regex

Bash itself does not know regex. Use programs like grep, sed, awk.

Control characters

Character	Description
`.`	Any single character
`[ac-e]`	1 character in enum
`[^ac-e]`	1 character not in enum
`^`	Start of string
`$`	End of string
`\d`	Digit
`\D`	Not a digit
`\s`	Whitespace
`\S`	Not a Whitespace
`\<`	Start of word
`\>`	End of word
`pattern?`	Quantifier 0 or 1
`pattern*`	Quantifier 0..n
`pattern+`	Quantifier 1..n
`pattern{x}`	Quantifier exactly x
`pattern{x,}`	Quantifier x..n
`pattern{x,y}`	Quantifier x..y
`pattern{,y}`	Quantifier 0..y

Grep

Command	Options	Description
`grep`	`pattern file`	Extended Regex
	`-E pattern file`	Extended Regex
	`-v pattern file`	Invert match
	`-w pattern file`	Word match
	`-i pattern file`	Ignore case

Stream redirection

> overwrite
>> append

Character	Description
`> file` or `1> file`	STDOUT to file
`< file`	Datei to STDIN
`2> file`	STDERR to file
`2>&1`	STDERR to same target as STDOUT
`> file 2>&1`	STDOUT and STDERR to file

Text Readers & Editors

Less

Command	Description
`q`	Quit
`R`	Refresh content
`F`	Auto scroll
`g number`	Go to line
`m lowercaseLetter`	Mark line
`' lowercaseLetter`	Go to mark
`/pattern`	Search forward
`?pattern`	Search backward
`n`	Next search result
`N`	Last search result
`ESC u`	Remove highlighting from search

VI

VI/VIM Editing

To leave editing mode press ESC.

Command	Description
`i`	insert before cursor
`a`	insert after cursor
`A`	insert at end of line
`o`	new line below
`O`	new line above
`u`	undo
`.`	repeat last command
`yy`	copy line
`5yy`	copy 5 lines
`p`	paste below
`P`	paste above
`x`	delete character
`5x`	delete 5 characters
`dd`	delete line
`5dd`	delete 5 lines
`:10,20d`	delete lines 10-20
`d0`	delete to line begin
`d$`	delete to line end

Navigation

Navigate as usual with arrow keys, home, end, pg up, pg dn.

Command	Description
`5G`	go to line 5
`H`	go to top of screen
`M`	go to middle of screen
`L`	go to end of screen
`5w`	move over 7 words
`5b`	move back 5 words

Other

Command	Description
`/foo`	search forward
`?foo`	search backwards
`n`	repeat search
`:w`	save
`:q`	close
`:wq`	save and close
`:q!`	close without saving
`:!command`	run bash command
`:r foo`	read file foo into this file

User and Group Management

UID

UID	Type
<1000	system account
>1000	user account

User Database

User info without passwords is stored in /etc/passwd.

username	PW	UID	GID	Kommentar	HOME	SHELL
hfict	x	1000	1000		/home/hfict	/bin/bash

Group Database

Group info with secondary group members are stored in /etc/group. Primary group members are identified by GID in user database.

groupname	PW	GID	Users
wheel	x	10	hfict,user2

Password Database

Hashed user passwords are stored in /etc/shadow. Password encryption is configured in /etc/login.defs.

username	PW	Last PW change	Minimum	Maximum	Warn	Inactive	Expire
hfict	[hash]	17803	0	99999	7

PW:

[hash] Encrypted test password
! [hash] Account locked
!! or * Account locked, no password set

** Commands **

Command	Param	Description
`id`	`username`	Show a user’s ID and groups
`who`		Show logged in users
`last`		Show last logins
`lastb`		Show last failed logins
`sudo`	`-u user command`	Execute command with user rights (default is root)
	`-i` or `su -`	Shell with root rights
`su`		Shell as root (non-login shell)
	`-`	Shell as root (login shell)
	`- user`	Shell as user
`useradd`	`-u 2101 -g primarygroup -c comment username`	Create user (without `-g`, new group will be created)
`usermod`	`-G group1, group2`	Define (overwrite) secondary groups
	`-ag group, group2`	Add secondary groups
	`-l username`	Change username
	`-L`	Lock Account
	`-U`	Unlock Account
	`-s shellpath`	Change shell
`userdel`	`-r username`	Delete user including home and mail spool
`passwd`	`username`	Change password (interactive)
`groupadd`	`groupname`	Create group (optionally set GID with `-g`)
`groupdel`	`groupname`	Delete group

File System Permissions

Permissions can be set on:

User (owner)
Group (owner)
Others

Only root can change User. User can change Group.

Basic permissions (Add binary flags to combine):

Char	Binary Flag	Permission
r	4	read
w	2	write
x	1	execute

Advanced permissions (place in front of basic permissions: chmod 1777 shared).:

Char	Binary Flag	Name	Description
t / T	1	Sticky Bit	Others can’t delete content (only applicable for directories)
s / S	2	SGID-Bit	File: run with permissions of Group Dir: New elements inherit Group
s / S	4	SUID-Bit	File is run with permissions of User (only applicable for files)

Advanced permissions replace the x when using ls -l. Lower case if x is set, upper case if x is not set.

Read permission on a directory only allows to see the directory itself but not it’s contents. Use execute permission to show contents.

Commands

Command	Options	Description
`chmod`	`-R [uog] dirname`	Set permissions recursively using binary flags
	`+[suog] filename`	Add permissions using binary flags
	`-[suog] filename`	Remove permissions using binary flags
	`u+x filename`	Add execute permission for User
	`g+wx filename`	Add write and execute permissions for Group
	`o-r filename`	Remove read permission for Others
`chown`	`-R user:group filename`	Change owner (User & Group) recursively
	`user filename`	Change owner (User)
	`:group filename`	Change owner (Group)
`chgroup`	`group filename`	Change owner (Group)

SSH

SSH Configuration is done in /etc/ssh/sshd_config.

Reload SSH service with systemctl reload sshd to apply changes!

DenyUsers, AllowUsers, DenyGroups, AllowGroups override each other and are applied in the order listed above.

Config	Option	Description
`PermitRootLogin`	`no`	Deny root to login via SSH
	`yes`	Allow root to login via SSH
	`without-password`	Allow only with private/public key auth
`AllowUsers`	`user1 user2`	Allow only user1 and user2
`DenyUsers`	`user1 user2`	Allow all users but user1 and user2
`AllowGroups`	`group1 group2`	Allow only users from specified groups
`DenyGroups`	`group1 group2`	Allow all users but those in specified groups

Cronjobs

Crontab

Cronjobs are configured in crontab files. Do not edit these files directly. Use crontab -e instead. This runs all required actions to activate a cronjob after saving the edited crontab. The locations are as follows:

/var/spool/cron/username user specific
/etc/crontab system wide crontab

The format of the files is (user specific crontabs do not have the column user-name):

Example of job definition:
.---------------- minute (0 - 59 | */5 [every 5 minutes])
|  .------------- hour (0 - 23)
|  |  .---------- day of month (1 - 31)
|  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
|  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
|  |  |  |  |
*  *  *  *  * user-name  command to be executed

Command	Description
`rpm -q cronie`	Check if package is installed
`systemctl status crond.service`	Check if service is running
`crontab -l`	List current users crontab
`crontab -e`	Edit current users crontab
`crontab -e -u username`	Edit specific users crontab
`crontab -r`	Remove current users crontab

Script folders

Scripts in one of the following directories will be executed at the intervall specified by the directory’s name:

/etc/cron.hourly
/etc/cron.daily
/etc/cron.weekly
/etc/cron.monthly

Allow / Deny usage

Add user names one per line to the following files:

/etc/cron.allow Whitelist
/etc/cron.deny Blacklist

If none of the files exists, all users are allowed.

Logs and Results

Execution of cronjobs is logged in /var/log/cron. Results are sent to the users mail /var/spool/mail/username.

Package Management

RPM

RPM

Command	Description
`rpm -i rpmfile\|rpmurl`	Install package
`rpm -e packagename`	Uninstall package
`rpm -q packagename`	Check if package is installed
`rpm -ql packagename`	List files in a package
`rpm -qa`	List all installed packages
`rpm -qf /path/to/file`	Get package that installed the file
`rpm -qf $(which <exe>)`	Get package that installed the executable
`rpm -V packagename`	Validate installed package

YUM

YUM is configured in /etc/yum.conf

Repos are configured in /etc/yum.repos.d/

Log is in /var/log/yum.log

Command	Description
`yum install packagename [-y]`	Install package (`-y` no confirm message)
`yum remove packagename`	Uninstall package
`yum update`	Update all installed packages
`yum update packagename`	Update specific package
`yum update pattern*`	Update packages using wildcard
`yum info packagename`	Get detailed info about package
`yum list packagename`	List installed and available packages
`yum search searchstring`	search for a package (name & summary)
`yum search all searchstring`	search for a package (all infos)
`yum deplist packagename`	List dependencies of a package
`yum reinstall packagename`	Reinstall (corrupted) package
`yumdownloader --resolve packagename`	Download rpm package with dependencies

List of commands by category:

If you want to contribute, feel free to pick up a topic marked as TODO and submit a pull request

Feel free to add new topics in case that you don’t find one that you like from the current list.

Directory Navigation

cd – change working directory
ls – list directory contents
dir – directory listing, columnar format
pwd – return working directory name
tree – list subdirectories in a tree structure

File Commands

cat/tac – concatenate and print files
diff/sdiff – compare files line by line
find – search for files
grep – file pattern matcher
head – display the first lines of a file
locate – find files and directories
stat – display file status
tail – display the last lines of a file
uniq – report or filter out repeated lines in a file

File and Directory Manipulation

awk – pattern-directed scanning and processing language
chmod – change permissions
chown – change file owner and group
cp – copy files and directories
cut – remove sections from files
mkdir – make a new directory
mv – move files and directories
nano – text editor
rm – delete files and directories
rmdir – remove directory
paste – merge corresponding or subsequent lines of file
rsync – remote copy files
scp – secure copy
basename – strips directory information and suffixes from file path
sed – text transformation tool
sort – arrange or merge lines of files
split – split a file into pieces
touch – change file access and modification times
vim – text editor

Package archive and compression tools

bzip2 – block-sorting file compressor
gzip – compression tool
gunzip – decompression tool
tar – create, extract and manipulate archives
zip – package and compress files
unzip – list, test, extract compressed ZIP files

System commands

crontab – maintain individual tables used to drive the cron daemon
df – display free disk space
du – display disk usage statistics
free – show memory usage information
hostname – set or print name of current host system
hostnamectl – change hostname settings
ionice – get/set I/O process priority
iostat – I/O statistics
kill – terminate or signal a process by id
killall – kill processes by name
lsblk – display block and loop devices
lsof – list open files
mpstat – CPU statistics
ncdu – curses-based disk usage
ps – display process status
pstree – show processes in tree format
reboot – restart the system
service – run an init script
shutdown – close down the system at a specific time
top/htop – display process information
uname – prints operating system details
useradd – add/update user accounts
userdel – delete user account
usermod – modify user properties
vmstat – virtual memory statistics
whereis – locate programs

Networking Commands

dig – DNS lookup utility
ifconfig – configure network interface parameters
ip – perform network administration tasks
iptable – configure IPv4 network firewall
lscpu – display CPU architecture information
netstat – show network status
ping – check network connectivity
whois – information about Internet domain names and network numbers

Package Management

apt – Debian package management
rpm – RPM package manager (RedHat)
yum – package manager for RedHat Linux

User Information commands

For user modification, see useradd, userdel, usermod under System commands

groups – show group memberships
finger – shows information about users
last – displays most recent user logins
passwd – modify a user’s password
w – display who is logged in and what they are doing
who – display who is logged in
whoami – display effective user id

Session commands

clear – clear terminal screen
env – display environment variables, or set variables for command execution
exit – close the active session/shell
printenv – print specified environment variables
history – display the command history
login – login and initiate a user session
nohup – invoke a utility immune to hangups
sleep – suspend execution for a time interval
ssh – secure shell login
su – substitute user identity
sudo – execute a command as another user
screen – start a screen session

Getting Help

man – format and display online manual pages
help – displays help about basic commands not covered by ‘man’
whatis – display one-line command descriptions

Applications

bc – basic calculator
cal – displays a calendar
cmatrix – enter the Matrix
curl – transfer data to or from a server
echo – display interpreted arguments
factor – prints prime factors of numbers
printf – format output
sl – runs a steam locomotive across your terminal
wget – non-interactive web file download
xargs – construct argument lists and execute utility
yes – print continous output stream
banner – Writes ASCII character strings in large letters to standard output.
aplay – aplay is a command-line to play audio files.
spd-say – plays the given text as the sound from the command line.

List of commands by chapter:

If you want to contribute, feel free to pick up a topic, update it with New Examples | [Options]and submit a pull request

Feel free to add new topics in case that you don’t find one that you like from the current list.

Contributing

If you are contributing please read the contributing file before submitting your pull requests.

Github Link

Facebook BugBounty Writeups

++101 Linux commands Open-source eBook

Download links

Basics

File Hierarchy Standard (FHS)

Commands

Disk and File System Management

General Disk Manipulation (non-LVM)

Globs (Wildcards)

Regex

Stream redirection

Text Readers & Editors

Less

VI

User and Group Management

File System Permissions

SSH

Cronjobs

Package Management

RPM

YUM

List of commands by category:

Getting Help

Applications

List of commands by chapter:

Links

Contributing