Linux Commands

Basic Commands

• ls, cp, mv, ps, kill, echo, cat, man, ifconfig

File Management

• cd dir – Change current directory to dir
• pwd – Print path of current working directory
• pushd, popd
• ls -l – print directory listing of current directory in long format
• ln -s target link-name – Create a symbolic link named link-name that points to target
• readlink
• cp file1 file2 – Copy file1 to file2
• cp -r src dest – Copy directory src to dest
• mv file1 file2 – Move or rename file1 to file2
• rm -f file(s) – Delete file(s)
• rm -rf dir – Remove directory dir and all of its contents
• mkdir dir – Create a directory named dir
• mkdir -p foo/bar/baz – Create a directory and all intermediate directories
• mknod, mkfifo
• touch file – Create an empty file named file
• df -h – Show disk free space
• du -sh dir – Show cumulative size of a directory
• stat, file
• chmod octal file – Change the permissions of file to octal
• chmod 777 file – make file readable, writable, and executable (rwx) for all users
• chmod +x file – make file executable
• chown user path – Change owner of file or directory
• chown user:group – Change owner and group of file or directory
• chown -R user dir – Change owner of directory and contents (recursively)
• chgrp
• cat file – Display the contents of file
• more file – Display file one page at a time; press spacebar to proceed to the next page
• less file – less is similar to more, but also allows moving backwards
• head -20 file – Display the first 20 lines of file
• tail -f file – Display the contents of file as it grows – This is especially usefull for following log files.
• vi, vim, nano, pico, emacs
• which command – give the full path to command
• find dir -type f -name 'foo*' – find all files in dir whose name starts with “foo” (note the single quotes, otherwise shell globing would occur)
• find . -type f -exec grep -l "foo" {} \; – find all files in the current directory containing “foo”
• locate file – find file
• diff -u file1 file2 – view the differences between two files
• diff -ur dir1 dir2 – view the differences between two directories

File System and Partitioning

• mount, umount
• lsblk, blockdev, fdisk, fsck, mkfs, resize2fs

Text and Stream Processing

• strings file – print all human readable strings in a binary file
• grep pattern file – find all lines in file that contain or match pattern
• dd
• pv, tee
• sed, awk, tr, cut, join, column, iconv
• wc -l file – count number of line in file
• nl, od, sort, uniq, fold, tac
• csplit, split
• xargs

File Compression

• tar zcvf archive.tar.gz files... – create a gzip-compressed archive
• tar zxvf archive.tar.gz – decompress and extract archived files to current directory
• gzip file.txt – compresses a file (creates file.txt.gz) and removes the original, uncompressed version
• gunzip file.txt.gz – uncompresses a file that was compressed with gzip or compress and removes the compressed version
• zip -r archive.zip files... – create a zip archive
• unzip archive.zip [-d destination_folder] – extract/decompress zip achive
• unzip -l archive.zip – list the contents of archive.zip
• zcat, zless, zmore, zgrep, zdiff – these ‘Z’ commands operate on gzip-compressed files and provide a ‘Z’ equivalent to their regular counterparts
  • zcat system.log.0.gz – view a compressed file
    • zcat is identical to gunzip -c
  • zless system.log.0.gz – ‘Z’ equivalent of less to view a compressed file

Getting Help

• man command – Show the manual for command
• help command – Use help for builtin commands
  • If you do not know if a command is a shell builtin or not, run type command.
• info command – for GNU/Linux commands, info often provides a more detailed documentation than the man page
• apropos subject – Search manual pages for subject
  • man -k is equivalent to the apropos command
• whatis command – Display one-line manual page descriptions
  • use help -d for a one-line description of a shell builtin
• which command – Show the full path of a command
• whereis command – locate the binary, source, and manual page files for a command

Process Management

• ps aux – list all processes on the system
• top, pstree
• kill, pkill, killall
• disown, nohup
• lsof, fuser

Managing System Services

• service, systemctl
• init, shutdown

User Management

• usermod, useradd, adduser, userdel, passwd
• groupmod, groupadd, gpasswd
• whoami – Show who you are logged in as
• id, getent, groups
• who, w, last

Network Commands

• ifconfig – List IP addresses and configuration of network interfaces
• ifdown, ifup
• dhclient -r eth0 – release current DHCP lease
• dhclient -v eth0 – obtain IP address from DHCP
• ip, route
• iptables
• wpa_supplicant
• iwlist – display information about wireless networks
• wpa_cli
• brctl, hostapd
• wget, curl
• ftp
• scp -P 5010 foo.txt user@adams204xx.hofstra.edu:/home/user/ – copy local file to linux home directory
• scp -P 5010 user@adams204xx.hofstra.edu:/home/user/foo.txt foo.txt – copy remote file to local system
• sftp, tftp, rsync
• ping, nmap, traceroute, arp, tcpdump
• nslookup domain – Perform DNS lookup of domain
• dig domain – Perform DNS lookup of domain
• ssh user@host – Connect to host as user
• ssh-keygen -t rsa -b 4096 – Generate a new SSH key-pair
• ssh-copy-id user@host – Copy your local key (usually ~/.ssh/id_rsa.pub by default) to the account for user on host to enable key-based (passwordless) authentication into the remote host

System Information

• uname -a – Show kernel information
• dmidecode
• lscpu, lspci, lsusb
• hostname
• date, uptime
• free – Show memory and swap usage

Printing

• lp, lpr

Environment

• env, chroot

Shell builtins

• cd, pwd
• clear
• exit
• history, fc
• type