Basic Linux Commands

Following are the useful linux commands: 

FILE 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 a directory dir
• rm file - delete file
• rm -r dir - delete directory dir
• rm -f file - force remove file
• rm -rf dir - force remove directory dir *
• cp file1 file2 - copy file1 to file2
• cp -r dir1 dir2 - copy dir1 to dir2; create dir2 if it doesn't exit
• mv file1 file2 - rename or move file1 to file2 if file2 is an existing directory, move file1 into directory file2
• ln -s file link - create symbolic link link to file
• touch file - create or update file
• cat > file - places standard input into file
• more file - output the contents of file
• head file - output the first 10 lines of file
• tail file - output the last 10 lines of file
• tail -f file - output the contents of file as it grows, starting with the last 10 lines

SEARCHING

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

PROCESS MANAGEMENT

• ps - display your currently active proceess
• top - display all running process
• kill pid - kill process id pid
• killall proc - kill all process named proc (use with extreme caution)
• bg - lists stopped or backgrpund jobs; resume a stopped job in the backgrpund
• fg - brings the most recent job to foreground
• fg n - brings job n to the foreground

SYSTEM INFO

• date - show the current date and time
• cal - show this month's calender
• uptime - show current uptime
• w - display who is online
• whoami - who you are logged in as
• finger user - display information about user
• uname -a - show kernel information
• cat /proc/cpuinfo - cpu information
• cat /proc/meminfo - memory information
• man command - show the manual for command
• df - show disk usage
• du - show directory space usage
• free - show memory and swap usage
• whereis app - show possible location of app
• which app - show which app will be run by default

COMPRESSION

• tar cf file.tar files - create a tar named file.tar containing files
• tar xf files.tar - extract the files from file.tar
• tar czf file.tar.gz files - create a tar with Gzip compression
• tar xzf file.tar.gz - extract a tar using Gzip
• tar cjf file.tar.bz2 - create a tar with Bzip2 compression
• tar xjf file.tar.bz2 - extract a tar using Bzip2
• gzip file - compress file and renamed it to file.gz
• gzip -d file.gz - decompress file.gz back to file

NETWORK

• ping host - ping host and output result
• whois domain - get whois information for domain
• dig domain - get DNS information for domain
• dig -x host - reverse lookup host
• wget file - download file
• wget -c file - continue a stopped download