Linux Commands

Inhalt

Command Overview
Commands by Category

Disks and Partitions
File Compression
File Permissions
Files and Directories
Hardware
Navigation
Network
Processes
Search
Shell Special Commands
System Information
Users and Groups

Depending on the distribution, some commands may need to be installed first, e.g. whois or dig.

Commands can accept many more parameters than listed here. All available parameters can be taken from the help with man [COMMAND]. The parameters can also be displayed with [COMMAND] --help or [COMMAND] -h.

Some commands or arguments require execution with the command sudo.

Command Overview

Command	Description
`!!`	Execute the last command ^!!!
`> [FILE]`	Create empty file ^!!!
`badblocks -s /dev/[DEVICE]`	Drive check ^sudo
`cal`	Shows current month calendar
`cat /etc/group`	Shows all groups
`cat /etc/passwd`	Shows all users
`cat /proc/cpuinfo`	CPU information
`cat [FILE]`	Output file content
`cat [SOURCE] >> [TARGET]`	Append file content to another file
`cd ..`	Go to parent directory
`cd [DIRECTORY]`	Go to a directory
`cd ~`	Go to home directory
`chmod [RIGHTS] [FILE]`	Change file permissions ^{sudo !!!}
`chown [USER] [FILE]`	Change file owner ^{sudo !!!}
`chown [USER]:[GROUP] [FILE]`	Change file owner and group ^{sudo !!!}
`cp -r [SOURCE] [DESTINATION]`	Copy a directory
`cp [SOURCE] [DESTINATION]`	Copy a file
`date`	Shows current date and time
`date -R`	Shows current date and time (RFC-5322)
`date -u`	Shows current date and time (UTC)
`df -h`	Shows free and used disk space
`dig [HOST] ANY`	Show DNS information
`dmesg`	Bootup messages ^sudo
`dmidecode`	System information ^sudo
`dmidecode --dump-bin [FILE]`	System information (dump to file) ^sudo
`dmidecode --from-dump [FILE]`	System information (read from file)
`du -ah [PATH]`	Shows disk usage
`exit`	Exit the current shell
`fdisk -l`	Shows partitions ^{sudo !!!}
`find [PATH] -name [EXPRESSION]`	Search for files in a directory
`findmnt`	List all file systems
`free -h`	Memory usage
`gpg -c [FILE]`	Encrypt a file
`gpg -d [FILE]`	Decrypt a file
`grep -Hnir [TERM] [DIRECTORY]`	Recursive search in a directory
`grep -i [TERM] [FILE]`	Search in a file
`groupadd [GROUP]`	Create new group ^sudo
`groupdel [GROUP]`	Remove a group ^{sudo !!!}
`groups`	Shows current groups
`gzip -d [FILE]`	Decompress file with GNU ZIP
`gzip -k [FILE]`	Compress file with GNU ZIP
`hdparm -g /dev/[DEVICE]`	Drive geometry ^{sudo !!!}
`hdparm -i /dev/[DEVICE]`	Drive information ^{sudo !!!}
`hdparm -tT /dev/[DEVICE]`	Drive read-speed test ^{sudo !!!}
`head [FILE]`	Shows the first 10 lines of a file
`hostname`	Shows the system hostname
`hostname -i`	Shows the system IP address
`id`	Shows current user information
`id -un`	Shows the own user name
`id [USER]`	Shows user information
`ip addr`	List IP addresses and network interfaces
`ip route`	Shows routing table
`kill [PID]`	Kill a process by its PID ^!!!
`killall [NAME]`	Kill all processes with a given name
`last`	Shows last logged in users
`last reboot`	Shows system reboot history
`less [FILE]`	Shows file content
`ln -s [TARGET] [NAME]`	Create a symbolic link
`locate [TERM]`	Search for files
`ls`	List files in directory
`ls -la`	List all files in directory
`lsblk`	Block devices
`lsof`	List all open files
`lspci`	PCI devices
`lspci -tv`	PCI devices (tree)
`lspci -v`	PCI devices (verbose)
`lsusb`	USB devices
`lsusb -tv`	USB devices (tree)
`lsusb -v`	USB devices (verbose)
`mkdir [DIRECTORY]`	Create new directory
`more [FILE]`	Shows file content
`mv [SOURCE] [DESTINATION]`	Rename or move a file or directory ^!!!
`ping [HOST]`	Ping a host
`pkill [NAME]`	Kill a process by its name ^!!!
`pmap [PID]`	Shows memory map o a process
`ps -aux`	Shows all processes
`pstree`	Shows processes (tree)
`pwd`	Shows current directory path
`rm -r [DIRECTORY]`	Remove directory ^!!!
`rm [FILE]`	Remove file ^!!!
`ss -ap`	Shows open ports
`tail [FILE]`	Shows the last 10 lines of a file
`tar cf [TARGET] [FILES]`	Compress files with TAR
`tar czf [TARGET] [FILES]`	Compress files with TAR and GNU ZIP
`tar xf [FILE]`	Extract files with TAR
`top`	Shows processes (in real-time)
`touch [FILE]`	Change file time ^!!!
`traceroute -I [HOST]`	Trace route to a host
`uname -a`	Shows system and kernel information
`uptime -p`	Shows system running time
`uptime -s`	Shows system start time
`useradd [USER]`	Create new user ^sudo
`userdel [USER]`	Remove user ^{sudo !!!}
`usermod -aG [GROUP] [USER]`	Add a user to groups ^{sudo !!!}
`users`	Shows logged in users
`w`	Shows logged in users and their activity
`wc [FILE]`	Count lines, words and bytes of a file
`who`	Shows logged in users
`who -b`	Shows system boot time
`whoami`	Shows the own user name
`whois [HOST]`	Get whois information

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Commands by Category

Disks and Partitions

df -h: Shows the free and used space on all file systems.
du -ah [PATH]: Shows the disk usage for the specified [PATH]. Without a path, the current path is used.
fdisk -l: Lists all partitions, sizes and types.
Execute with sudo / Caution when using
findmnt: Lists all file systems.

File Compression

gzip -d [FILE]: Decompresses a [FILE] with GNU ZIP.
gzip -k [FILE]: Compresses a [FILE] with GNU ZIP and store the compressed file as "[FILE].gz". Without the option "-k", the original file will be removed.
tar cf [TARGET] [FILES]: Compresses one or more [FILES] with TAR and store it as [TARGET] file (e.g. "archive.tar").
tar czf [TARGET] [FILES]: Compresses one or more [FILES] with TAR and GNU ZIP and store it as [TARGET] file (e.g. "archive.tar.gz").
tar xf [FILE]: Extracts files from a TAR [FILE].

File Permissions

chmod [RIGHTS] [FILE]: Changes the file permissions for a [FILE]. The [RIGHTS] can be entered as octal code (digits 0-7) in the order owner-group-others. Rights: 4=read, 2=write, 1=execute, 0=none. Examples: 777=all rights for all users, 644=read and write for owner, read only for all other.
Execute with sudo / Caution when using
chown [USER] [FILE]: Changes the owner of the [FILE] to the specified [USER].
Execute with sudo / Caution when using
chown [USER]:[GROUP] [FILE]: Changes the owner and the [GROUP] of the [FILE] to the specified [USER].
Execute with sudo / Caution when using

Files and Directories

> [FILE]: Creates a new empty [FILE]. If the [FILE] exists, it's size will be set to 0.
Caution when using
cat [FILE]: Outputs the content of a [FILE].
cat [SOURCE] >> [TARGET]: Appends the content of one or more [SOURCE] files to a [TARGET] file.
cp -r [SOURCE] [DESTINATION]: Copies a [SOURCE] directory to a [DESTINATION] directory with its entire content.
cp [SOURCE] [DESTINATION]: Copies a [SOURCE] file to a [DESTINATION] file or directory.
gpg -c [FILE]: Encrypts a [FILE]. Password will be prompted.
gpg -d [FILE]: Decrypts a [FILE].
head [FILE]: Shows the first 10 lines of a [FILE].
less [FILE]: Shows the content of a [FILE]. Lines and/or pages are scrollable.
ln -s [TARGET] [NAME]: Creates a symbolic link with the given [NAME] to a [TARGET] file or directory.
mkdir [DIRECTORY]: Creates a new [DIRECTORY].
more [FILE]: Shows the content of a [FILE]. Lines and/or pages are scrollable.
mv [SOURCE] [DESTINATION]: Moves a [SOURCE] file or directory to a new [DESTINATION] or rename it.
Caution when using
pwd: Prints full path of the current working directory.
rm -r [DIRECTORY]: Removes a [DIRECTORY] with its entire content.
Caution when using
rm [FILE]: Removes the specified [FILE].
Caution when using
tail [FILE]: Shows the last 10 lines of a [FILE].
touch [FILE]: Changes the access and modification time of a [FILE] to the current time. touch creates the [FILE], if it does not exist.
Caution when using
wc [FILE]: Counts lines, words and bytes in the content of a [FILE].

Hardware

badblocks -s /dev/[DEVICE]: Checks a [DEVICE] for unreadable blocks.
Execute with sudo
cat /proc/cpuinfo: Shows CPU information.
dmesg: Shows messages from system bootup.
Execute with sudo
dmidecode: Shows information about BIOS, system, mainboard and chassis.
Execute with sudo
dmidecode --dump-bin [FILE]: Dumps information about BIOS, system, mainboard and chassis in a binary file.
Execute with sudo
dmidecode --from-dump [FILE]: Shows information about BIOS, system, mainboard and chassis from a binary dump file.
free -h: Shows free and used memory.
hdparm -g /dev/[DEVICE]: Shows drive geometry of the specified [DEVICE].
Execute with sudo / Caution when using
hdparm -i /dev/[DEVICE]: Shows drive information about the specified [DEVICE].
Execute with sudo / Caution when using
hdparm -tT /dev/[DEVICE]: Performs a read-speed test for the specified [DEVICE].
Execute with sudo / Caution when using
lsblk: Shows information about block devices.
lspci: Shows information about PCI devices.
lspci -tv: Shows information about PCI devices as tree.
lspci -v: Shows verbose information about PCI devices.
lsusb: Shows information about USB devices.
lsusb -tv: Shows information about USB devices as tree.
lsusb -v: Shows verbose information about USB devices.

Navigation

cd ..: Goes to the parent directory.
cd [DIRECTORY]: Goes to the specified [DIRECTORY].
cd ~: Goes to the users hone directory.

Network

dig [HOST] ANY: Shows DNS information for a [HOST].
ip addr: Shows addresses assigned to all network interfaces.
ip route: Shows the routing table.
ping [HOST]: Performs a ping to a given [HOST].
ss -ap: Shows a list with all open sockets, including the ports and the processes using these sockets.
traceroute -I [HOST]: Traces the route to a [HOST] per ICMP ECHO.
whois [HOST]: Shows whois information for a [HOST].

Processes

kill [PID]: Kills a process with the specified [PID].
Caution when using
killall [NAME]: Kills all processes with the specified [NAME].
lsof: Lists all files opened by running processes.
pkill [NAME]: Kills a process with the specified [NAME].
Caution when using
pmap [PID]: Shows the memory map of the process specified by its [PID].
ps -aux: Shows all processes running on the system.
pstree: Shows running processes as tree.
top: Shows running processes in real-time.

Search

find [PATH] -name [EXPRESSION]: Searches in a given [PATH] for file names with the specified [TERM] (incl. placeholders like "*" and "?").
grep -Hnir [TERM] [DIRECTORY]: Searches recursive for a case-invariant [TERM] in all files of a [DIRECTORY] and display the filename and line number.
grep -i [TERM] [FILE]: Searches for a [TERM] in a [FILE].
locate [TERM]: Search for file names with a given [TERM].
ls: Lists files in the current directory.
ls -la: Lists all files in the current directory with additional information.

Shell Special Commands

!!: Executes the last command.
Caution when using
exit: Exits the current shell.

System Information

cal: Shows a calendar for the current month. The parameter "-w" adds week numbers.
date: Shows the current date and time.
date -R: Shows the current date and time in the RFC-5322 format.
date -u: Shows the current date and time as Coordinated Universal Time (UTC).
hostname: Shows the hostname of the system.
hostname -i: Shows the IP address of the system.
last reboot: Shows a list with the last system reboots.
uname -a: Shows system and kernel information like operating system name and version, machine name and kernel release.
uptime -p: Shows how long the system has been running.
uptime -s: Shows the date and time since the system is running.

Users and Groups

cat /etc/group: Shows the file "/etc/group" with all group names and group IDs.
cat /etc/passwd: Shows the file "/etc/passwd" with all user names and user IDs.
groupadd [GROUP]: Creates a new group with the specified [GROUP] name.
Execute with sudo
groupdel [GROUP]: Removes the group specified by [GROUP].
Execute with sudo / Caution when using
groups: Shows the current group names.
id: Shows user and group information for the current user.
id -un: Shows the own user name. Same as "whoami".
id [USER]: Shows user and group information for the specified [USER].
last: Shows a list with the last logged in users.
useradd [USER]: Creates a new user with the specified [USER] name.
Execute with sudo
userdel [USER]: Removes the user specified by [USER].
Execute with sudo / Caution when using
usermod -aG [GROUP] [USER]: Adds a [USER] to the specified [GROUP]. Without option "-a" all other groups of the user will be replaced with the new group!
Execute with sudo / Caution when using
users: Shows the currently logged in users.
w: Shows a list with the currently logged in users and their activity.
who: Shows a list with the currently logged in users.
who -b: Shows the date and time of the last system boot.
whoami: Shows the own user name. Same as "id -un".

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