Essential Linux Command Cheat Sheet for System Administration

This article provides a comprehensive reference of common Linux commands for system administration.

1. Basic Commands

uname -m               # display processor architecture</code>
<code>uname -r               # display kernel version</code>
<code>dmidecode -q          # show hardware components</code>
<code>hdparm -i /dev/hda    # list disk characteristics</code>
<code>hdparm -tT /dev/sda   # perform a read test on a disk</code>
<code>cat /proc/cpuinfo     # display CPU information</code>
<code>cat /proc/interrupts # show interrupts</code>
<code>cat /proc/meminfo     # check memory usage</code>
<code>cat /proc/swaps       # list active swap spaces</code>
<code>cat /proc/version     # display kernel version</code>
<code>cat /proc/net/dev     # show network interfaces and statistics</code>
<code>cat /proc/mounts      # list mounted filesystems</code>
<code>lspci -tv            # list PCI devices</code>
<code>lsusb -tv            # show USB devices</code>
<code>date                  # display system date</code>
<code>cal 2007              # show calendar for 2007</code>
<code>date 041217002007.00  # set date and time (MMDDhhmmYY.ss)</code>
<code>clock -w              # write system time to BIOS

2. Shutdown and Reboot

shutdown -h now       # halt immediately</code>
<code>init 0                # halt (alternative)</code>
<code>telinit 0            # halt (alternative)</code>
<code>shutdown -h HH:MM    # schedule shutdown</code>
<code>shutdown -c          # cancel scheduled shutdown</code>
<code>shutdown -r now       # reboot immediately</code>
<code>reboot               # reboot</code>
<code>logout               # log out

3. Files and Directories

cd /home              # change to /home</code>
<code>cd ..                 # go up one level</code>
<code>cd ../..              # go up two levels</code>
<code>cd ~                  # go to home directory</code>
<code>cd ~user1            # go to user1's home</code>
<code>cd -                 # return to previous directory</code>
<code>pwd                  # print working directory</code>
<code>ls                   # list files</code>
<code>ls -F                # list with file type indicators</code>
<code>ls -l                # long format listing</code>
<code>ls -a                # show hidden files</code>
<code>ls *[0-9]*           # list names containing digits</code>
<code>tree                 # display directory tree</code>
<code>mkdir dir1           # create directory</code>
<code>mkdir -p /tmp/dir1/dir2 # create nested directories</code>
<code>rm -f file1          # force delete a file</code>
<code>rmdir dir1           # remove empty directory</code>
<code>rm -rf dir1          # delete directory and its contents</code>
<code>mv dir1 new_dir      # rename or move directory</code>
<code>cp file1 file2        # copy a file</code>
<code>ln -s file1 link1    # create symbolic link</code>
<code>ln file1 link1       # create hard link</code>
<code>touch -t 0712250000 file1 # set timestamp (YYMMDDhhmm)</code>
<code>file file1           # display file type</code>
<code>iconv -l             # list known encodings</code>
<code>iconv -f from -t to inputFile > outputFile # convert encoding</code>
<code>find . -maxdepth 1 -name "*.jpg" -exec convert "{}" -resize 80x60 "thumbs/{}" \; # batch resize images

4. File Search

find / -name file1                # search from root</code>
<code>find / -user user1                # files owned by user1</code>
<code>find /home/user1 -name "*.bin"   # search for .bin files</code>
<code>find /usr/bin -type f -atime +100 # files not accessed in 100 days</code>
<code>find /usr/bin -type f -mtime -10 # files modified within 10 days</code>
<code>find / -name "*.rpm" -exec chmod 755 "{}" \; # set permissions</code>
<code>locate "*.ps"                    # locate .ps files (requires updatedb)</code>
<code>whereis halt                     # locate binary, source, man page</code>
<code>which halt                       # show full path of executable

5. Mounting Filesystems

mount /dev/hda2 /mnt/hda2          # mount partition</code>
<code>umount /dev/hda2                  # unmount partition</code>
<code>fuser -km /mnt/hda2               # force unmount if busy</code>
<code>mount -o loop file.iso /mnt/cdrom # mount ISO image</code>
<code>mount -t vfat /dev/hda5 /mnt/hda5 # mount FAT32 filesystem</code>
<code>mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share # mount Windows share

6. Disk Space

df -h                     # show mounted partitions</code>
<code>du -sh dir1               # estimate disk usage of dir1</code>
<code>du -sk * | sort -rn      # list files/directories by size</code>
<code>rpm -qa --qf '%10{SIZE}t%{NAME}
' | sort -k1,1n # list RPM packages by size</code>
<code>dpkg-query -W -f='${Installed-Size}\t${Package}
' | sort -k1,1n # list DEB packages by size

7. Users and Groups

groupadd group_name        # create group</code>
<code>groupdel group_name        # delete group</code>
<code>useradd -c "Name" -g admin -d /home/user1 -s /bin/bash user1 # add user to admin group</code>
<code>passwd user1               # change user password</code>
<code>chage -E 2005-12-31 user1 # set password expiration date</code>
<code>newgrp group_name          # switch to a new primary group

8. File Permissions

chmod ugo+rwx directory1    # give read/write/execute to all</code>
<code>chmod go-rwx directory1    # remove rwx from group and others</code>
<code>chown user1 file1          # change file owner</code>
<code>chown -R user1 directory1 # recursively change owner</code>
<code>chmod u+s /bin/file1       # set SUID bit</code>
<code>chmod g+s /home/public    # set SGID on directory</code>
<code>chmod o+t /home/public    # set sticky bit</code>
<code>chmod +x file            # make executable

9. Special File Attributes

chattr +i file1            # make immutable</code>
<code>chattr +a file1            # append‑only</code>
<code>lsattr                    # list special attributes

10. Archiving and Compression

bzip2 file1                # compress with bzip2</code>
<code>gzip -9 file1              # maximum gzip compression</code>
<code>tar -cvf archive.tar file1 # create tarball</code>
<code>tar -xvf archive.tar      # extract tarball</code>
<code>zip file1.zip file1        # create zip archive</code>
<code>unzip file1.zip            # extract zip archive

11. RPM Package Management

rpm -ivh package.rpm       # install RPM</code>
<code>rpm -Uvh package.rpm      # upgrade RPM</code>
<code>rpm -e package_name       # erase RPM</code>
<code>rpm -qa                   # list installed RPMs</code>
<code>rpm -qf /etc/httpd/conf/httpd.conf # find owning package

12. YUM Package Manager

yum install package_name   # install package</code>
<code>yum update package_name   # update package</code>
<code>yum remove package_name   # remove package</code>
<code>yum list                  # list all packages</code>
<code>yum clean all             # clean cache

13. DEB Package Management

dpkg -i package.deb       # install DEB</code>
<code>dpkg -r package_name    # remove DEB</code>
<code>apt-get install pkg     # install via APT</code>
<code>apt-get update           # update package lists</code>
<code>apt-get upgrade          # upgrade all packages

14. Viewing File Contents

cat file1                 # display file</code>
<code>more file1                # paginate output</code>
<code>less file1                # paginate with backward navigation</code>
<code>head -2 file1            # first two lines</code>
<code>tail -f /var/log/messages # follow log file

15. Text Processing

grep pattern file         # search for pattern</code>
<code>sed 's/old/new/g' file   # replace text</code>
<code>awk '{print $1}' file    # print first column</code>
<code>sort file | uniq         # unique sorted lines</code>
<code>tr 'a-z' 'A-Z'           # translate to uppercase

16. Character Set Conversion

dos2unix file.txt          # convert DOS to UNIX line endings</code>
<code>unix2dos file.txt          # convert UNIX to DOS line endings

17. Filesystem Analysis

badblocks -v /dev/hda1    # check for bad blocks</code>
<code>fsck /dev/hda1           # check/repair filesystem

18. Initialize Filesystem

mkfs /dev/hda1            # create filesystem</code>
<code>mke2fs -j /dev/hda1      # create ext3 with journaling

19. Swap Management

mkswap /dev/hda3          # create swap area</code>
<code>swapon /dev/hda3          # enable swap

20. Backup and Restore

dump -0aj -f /tmp/home0.bak /home # full backup of /home</code>
<code>restore -if /tmp/home0.bak          # restore backup</code>
<code>rsync -av --delete /home /tmp       # synchronize directories</code>
<code>dd if=/dev/sda of=/tmp/image.img      # disk image copy

21. CD/DVD Operations

mkisofs -o cd.iso /data   # create ISO image</code>
<code>cdrecord dev=/dev/cdrom cd.iso # burn ISO</code>
<code>mount -o loop cd.iso /mnt/iso # mount ISO

22. Network Commands

ifconfig eth0            # show interface config</code>
<code>ifup eth0                # bring interface up</code>
<code>ifdown eth0              # bring interface down</code>
<code>route -n                # display routing table</code>
<code>netstat -tup            # list active connections</code>
<code>tcpdump -i eth0 port 80 # capture HTTP traffic</code>
<code>nslookup www.example.com # DNS lookup

23. Listing Directory Contents

ls -a                    # all files including hidden</code>
<code>ls -l                    # long format</code>
<code>ls -R                    # recursive

24. Determine File Type

file filename            # show file type

25. Copying Files and Directories

cp source dest           # copy file</code>
<code>cp -r src_dir dest_dir   # copy directory recursively</code>
<code>mv oldname newname       # rename or move</code>
<code>rm -rf dir               # delete directory tree

26. Common System Commands

date                     # show current date/time</code>
<code>uptime                   # show system uptime</code>
<code>who                      # list logged‑in users</code>
<code>dmesg                    # kernel ring buffer</code>
<code>free                     # memory usage

27. VIM Editor

vim file                 # open file in VIM</code>
<code>:q                      # quit VIM</code>
<code>:w                      # write (save) file</code>
<code>:wq                     # write and quit</code>
<code>i                       # enter insert mode</code>
<code>Esc                     # return to command mode

28. RPM Package Operations

rpm -ivh package.rpm    # install</code>
<code>rpm -e package_name    # erase</code>
<code>rpm -Uvh package.rpm   # upgrade</code>
<code>rpm -Fvh package.rpm   # update</code>
<code>rpm -q package_name    # query</code>
<code>rpm -ql package_name   # list files in package