Essential Linux Commands
Most-commonly used Linux commands
This article presents the essential commands for Linux. These basic Linux commands will help the novice user to work successfully with Unix systems.
System Info commands
date – show the current date and time
cal – show this month's calendar
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 locations of app
which app – show which app will be run by default
cal – show this month's calendar
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 locations of app
which app – show which app will be run by default
File and Directories Commands
Directories commands
ls – directory listing
cd dir - change directory to dir
cd – change to home
pwd – show current directory
mkdir dir – create a directory dir
rm -r dir – delete directory dir
rm -rf dir – force remove directory dir *
cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it doesn't exist
cd dir - change directory to dir
cd – change to home
pwd – show current directory
mkdir dir – create a directory dir
rm -r dir – delete directory dir
rm -rf dir – force remove directory dir *
cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it doesn't exist
Files commands
ls -al – formatted listing with hidden files
rm file – delete file
rm -f file – force remove file
cp file1 file2 – copy file1 to file2
mv file1 file2 – rename or move file1 to file2 if file2 is an existing directory, moves file1 into irectory file2
ln -s file link – create symbolic link link to file
touch file – create or update file
rm file – delete file
rm -f file – force remove file
cp file1 file2 – copy file1 to file2
mv file1 file2 – rename or move file1 to file2 if file2 is an existing directory, moves file1 into irectory file2
ln -s file link – create symbolic link link to file
touch file – create or update file
Text commands in file
head file – output the first 10 lines of file
more file – output the contents of file
cat > file – places standard input into 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
more file – output the contents of file
cat > file – places standard input into 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
Process Management commands
ps – display your currently active processes
top – display all running processes
kill pid – kill process id pid
killall proc – kill all processes named proc *
bg – lists stopped or background jobs; resume a stopped job in the background
fg – brings the most recent job to foreground
fg n – brings job n to the foreground
top – display all running processes
kill pid – kill process id pid
killall proc – kill all processes named proc *
bg – lists stopped or background jobs; resume a stopped job in the background
fg – brings the most recent job to foreground
fg n – brings job n to the foreground
Network commands
ping host – ping host and output results
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
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
Installation
Install from source:
./configure
make
make install
dpkg -i pkg.deb – install a package (Debian)
rpm -Uvh pkg.rpm – install a package (RPM)
./configure
make
make install
dpkg -i pkg.deb – install a package (Debian)
rpm -Uvh pkg.rpm – install a package (RPM)
Useful keypresses/Shortcuts
Ctrl+C – halts the current command
Ctrl+Z – stops the current command, resume with fg in the foreground or bg in the background
Ctrl+D – log out of current session, similar to exit
Ctrl+W – erases one word in the current line
Ctrl+U – erases the whole line
Ctrl+R – type to bring up a recent command
!! - repeats the last command
exit – log out of current session
Ctrl+Z – stops the current command, resume with fg in the foreground or bg in the background
Ctrl+D – log out of current session, similar to exit
Ctrl+W – erases one word in the current line
Ctrl+U – erases the whole line
Ctrl+R – type to bring up a recent command
!! - repeats the last command
exit – log out of current session
Searching commands
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
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
Conclusion
We hope that the above commands will help a novice user to work quickly and correctly with the Linux system. These commands allow you to work with files and directories, create, delete and output the data you need.