Linux Commands

File CommandsFile Commands

• ls - directory listing
• ls -al - Formatted listing with hidden files
• cd dir - change directory to dir
• cd - change to home
• pwd - show current directory
• mkdir dir - create directory dir
• rm file - delete file
• rm -r dir - delete directory dir
• rm -f file - force remove file
• rm -rf dir - remove directory dir
• cp file1 file2 - copy file1 to file2
• mv file1 file2 - rename file1 to file2
• ln -s file link - create symbolic link 'link' to file
• touch file - create or update file
• cat > file - place standard input into file (ctrl+z to exit)
• more file - output the contents of the file
• less file - output the contents of the file
• head file - output first 10 lines of file
• tail file - output last 10 lines of file
• tail -f file - output contents of file as it grows

SSH

• ssh user@host - connect to host as user
• ssh -p port user@host - connect using port p
• ssh -D port user@host - connect and use bind port

Installation

• ./configure
• make
• make install

Network

• ping host - ping host 'host'
• whois domain - get whois for domain
• dig domain - get DNS for domain
• dig -x host - reserve lookup host
• wget file - download file
• wget -c file - continue stopped download
• wget -r url - recursively download files from url

System Info

• date - show current date/time
• cal - show this month's calendar
• uptime - show uptime
• w - display who is online
• whoami - who are you logged in as
• uname - a - show kernel configure
• cat /proc/cpuinfo - cpu info
• cat /proc/meminfo - memory information
• man command - show manual for command
• df - show disk usage
• du - show directory space usage

SearchingSearching

• grep pattern files - search for pattern in files
• grep -r pattern dir - search recursively for pattern in dir
• command I grep pattern - search for for pattern in the output of command
• locate file - find all instances of file

Process management

• ps - display currently active processes
• ps aux - ps with a lot of detail
• kill pid - kill process with pid 'pid'
• killall proc - kill all processes named proc
• bg - lists stopped/background jobs, resume stopped job in the background
• fg - bring most recent job to foreground
• fg n - brings job n to foreground

File PermissionsFile Permissions

chmod octal file - change permisssion of file 4 - read(r) 2 - write(w) 1 - execute(x) order :- owner/group/world eg: chmod 777 - rwx for everyone chmod 755 - rw for owner, rx for group/world

Compression

• tar cf file.tar files - tar files into file.tar
• tar xf file.tar - untar into current directory
• tar tf file.tar - show contents of archive tar flags: c - create archive j - bzip2 compression t - tables of contents k - do not overrite x - extract T - files from file f - specifies filename w - ask for confirmation z - use zip/gzip v - verbose
• gzip file - compress file and rename to file.gzip
• gzip -d file.gz - decompress file.gz
• tar -czvf name-of-archive.tar.gz /path/to/directory-or-file - Compress an Entire Directory or a .tar.gz Single File tar.gz flags: c - Create an archive. z - Compress the archive with gzip. v - Display progress in the terminal while creating the archive, also known as “verbose” mode. The v is always optional in these commands, but it's helpful. f - Allows you to specify the filename of the archive.
• tar -xzvf archive.tar.gz -C /destination - Extract an Archive
• zip -r file.zip directory/ -x *.zip* *.tar* *.git* *media* *var* - Excluede direcotory and file into zip

Shortcuts

• ctrl+c - halts current command
• ctrl+z - stops current command
• fg - resume stopped command in foreground
• bg - resume stopped command in background
• ctrl+d - log out of current session
• ctrl+w - erases one word in current lines
• ctrl+r - reverse lookup of previous commands

Various directories

• /bin/ : This contains commands used by a regular user.
• /boot/ : The files required for the operating system startup are stored here.
• /cdrom/ : When CD-ROM is mounted, the CD-ROM files are accessible here.
• /dev/ : The device driver files are stored in this folder. These device driver files will point to hardware-related programs running in kernel.
• /etc/ : This folder contains configuration files and startup scripts.
• /home/ : This folder contains a home folder of all users except the administrator.
• /lib/ : The library files are stored in this folder.
• /media/ : External media such as a USB pen drive is mounted in this folder.
• /opt/ : The optional packages are installed in this folder.
• /proc/ : This contains files which give information about kernel and every process running in OS.
• /root/ : This is the administrators home folder.
• /sbin/ : This contains commands used by the administrator or root user.
• /usr/ : This contains secondary programs, libraries, and documentation about user-related programs.
• /var/ : This contains variable data such as http, tftp, and similar other.
• /sys/ : This dynamically creates the sys files