Essential Linux Command Cheat Sheet: 100+ Commands Every Sysadmin Needs

1. Basic Commands

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

2. Shutdown and Reboot

shutdown -h now                # immediate shutdown
init 0                         # shutdown (method 2)
shutdown -h 23:30             # schedule shutdown at 23:30
shutdown -c                   # cancel scheduled shutdown
shutdown -r now                # immediate reboot
reboot                         # reboot the system
logout                         # log out

3. File and Directory Operations

cd /home                     # change to /home directory
cd ..                       # go up one level
cd ../..                    # go up two levels
cd ~user1                   # go to user1's home directory
cd -                        # return to previous directory
pwd                         # show current working directory
ls                          # list files in current directory
ls -F                       # list files with type indicators
ls -l                       # detailed file list
ls -a                       # show hidden files
ls *[0-9]*                  # list files/directories containing numbers
tree                        # display directory tree
lstree                      # alternative tree view
mkdir dir1                  # create directory dir1
mkdir dir1 dir2             # create two directories simultaneously
mkdir -p /tmp/dir1/dir2    # create nested directory tree
rm -f file1                 # force delete file1
rmdir dir1                  # remove empty directory dir1
rm -rf dir1                 # delete directory dir1 and its contents recursively
mv dir1 new_dir             # rename/move directory
cp file1 file2              # copy file1 to file2
cp dir/* .                  # copy all files from dir to current directory
cp -a /tmp/dir1 .          # copy directory preserving attributes
ln -s file1 lnk1            # create symbolic link to file1
ln file1 lnk1               # create hard link to file1
touch -t 0712250000 file1  # set file timestamp (YYMMDDhhmm)
file file1                  # display MIME type of file1

4. File Search

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

5. Mounting Filesystems

mount /dev/hda2 /mnt/hda2               # mount partition hda2
umount /dev/hda2                       # unmount partition
fuser -km /mnt/hda2                    # force unmount if busy
umount -n /mnt/hda2                    # unmount without writing /etc/mtab
mount /dev/fd0 /mnt/floppy              # mount floppy disk
mount /dev/cdrom /mnt/cdrom            # mount CD/DVD
mount /dev/hdc /mnt/cdrecorder         # mount CD-RW or DVD-RW
mount -o loop file.iso /mnt/cdrom      # mount ISO image
mount -t vfat /dev/hda5 /mnt/hda5      # mount FAT32 filesystem
mount /dev/sda1 /mnt/usbdisk           # mount USB flash drive
mount -t smbfs -o username=user,password=pass //WinClient/share /mnt/share  # mount Windows share

6. Disk Space

df -h                     # display mounted partitions and usage
ls -lSr | more           # list files sorted by size
du -sh dir1               # estimate disk usage of dir1
du -sk * | sort -rn      # sort directories/files by size
rpm -q -a --qf '%10{SIZE}t%{NAME}
' | sort -k1,1n   # list installed RPM packages by size
dpkg-query -W -f='${Installed-Size}\t${Package}
' | sort -k1,1n   # list installed DEB packages by size

7. Users and Groups

groupadd group_name               # create new group
groupdel group_name               # delete group
groupmod -n new_name old_name    # rename group
useradd -c "Name Surname" -g admin -d /home/user1 -s /bin/bash user1   # add user to admin group
useradd user1                    # add new user
userdel -r user1                 # delete user and home directory
usermod -c "User FTP" -g system -d /ftp/user1 -s /bin/nologin user1   # modify user attributes
passwd                           # change password
passwd user1                     # change password for user1
chage -E 2005-12-31 user1       # set password expiration date
pwck                             # verify /etc/passwd format
grpck                            # verify /etc/group format
newgrp group_name                # switch to new group

8. File Permissions

ls -lh                         # show permissions
chmod ugo+rwx directory1        # give read/write/execute to user, group, others
chmod go-rwx directory1         # remove read/write/execute from group and others
chown user1 file1               # change file owner
chown -R user1 directory1      # change owner recursively
chgrp group1 file1             # change group ownership
chown user1:group1 file1        # change owner and group
find / -perm -u+s             # list files with SUID bit set
chmod u+s /bin/file1           # set SUID on a binary
chmod u-s /bin/file1           # remove SUID
chmod g+s /home/public         # set SGID on a directory
chmod g-s /home/public         # remove SGID
chmod o+t /home/public         # set sticky bit on a directory
chmod o-t /home/public         # remove sticky bit
chmod +x file_path             # add execute permission
chmod -x file_path             # remove execute permission

9. Special File Attributes

chattr +a file1   # allow only append writes
chattr +c file1   # enable automatic compression
chattr +d file1   # exclude from dump backups
chattr +i file1   # make immutable (cannot delete/modify)
chattr +s file1   # enable secure deletion
chattr +S file1   # write changes immediately to disk
chattr +u file1   # allow recovery after deletion
lsattr            # list special attributes

10. Compression and Archiving

bunzip2 file1.bz2               # decompress bzip2 file
bzip2 file1                     # compress file with bzip2
gunzip file1.gz                 # decompress gzip file
gzip file1                      # compress file with gzip
gzip -9 file1                   # maximum compression
rar a file1.rar test_file       # create RAR archive
rar a file1.rar file1 file2 dir1   # add multiple files/directories to RAR
rar x file1.rar                # extract RAR archive
unrar x file1.rar              # extract RAR archive
tar -cvf archive.tar file1      # create uncompressed tarball
tar -cvf archive.tar file1 file2 dir1   # create tarball with multiple items
tar -tf archive.tar             # list contents of tarball
tar -xvf archive.tar           # extract tarball
tar -xvf archive.tar -C /tmp   # extract to specific directory
tar -cvfj archive.tar.bz2 dir1  # create bzip2-compressed tarball
tar -xvfj archive.tar.bz2      # extract bzip2-compressed tarball
tar -cvfz archive.tar.gz dir1  # create gzip-compressed tarball
tar -xvfz archive.tar.gz       # extract gzip-compressed tarball
zip file1.zip file1            # create zip archive
zip -r file1.zip file1 file2 dir1   # recursively zip multiple items
unzip file1.zip                # extract zip archive

11. RPM Package Management

rpm -ivh package.rpm                 # install RPM package
rpm -ivh --nodeps package.rpm        # install ignoring dependencies
rpm -U package.rpm                   # upgrade package without changing config files
rpm -F package.rpm                   # upgrade already installed package
rpm -e package_name.rpm              # erase package
rpm -qa                              # list all installed RPMs
rpm -qa | grep httpd                # filter installed RPMs containing "httpd"
rpm -qi package_name                # show detailed info about installed package
rpm -qg "System Environment/Daemons" # list RPMs in a group
rpm -ql package_name                 # list files provided by installed package
rpm -qc package_name                 # list config files of installed package
rpm -q package_name --whatrequires   # show packages that depend on this one
rpm -q package_name --whatprovides   # show what this package provides
rpm -q package_name --scripts        # show install/remove scripts
rpm -q package_name --changelog      # show changelog
rpm -qf /etc/httpd/conf/httpd.conf  # find which RPM provides a file
rpm -qp package.rpm -l                # list files in an uninstalled RPM
rpm --import /media/cdrom/RPM-GPG-KEY # import GPG key
rpm --checksig package.rpm            # verify package signature
rpm -V package_name                  # verify package files
rpm -Va                               # verify all installed packages (use with care)
rpm -Vp package.rpm                   # verify an uninstalled RPM
rpm2cpio package.rpm | cpio --extract --make-directories *bin*   # extract executable from RPM
rpm -ivh /usr/src/redhat/RPMS/$(arch)/package.rpm   # install built RPM from source
rpmbuild --rebuild package_name.src.rpm               # rebuild source RPM

12. YUM Package Management

yum install package_name               # download and install RPM package
yum localinstall package_name.rpm      # install local RPM with dependency resolution
yum update package_name.rpm            # update all installed RPMs
yum update package_name                # update specific package
yum remove package_name                # remove RPM package
yum list                               # list all installed packages
yum search package_name                # search repository for package
yum clean packages                     # clean package cache
yum clean headers                      # clean header files
yum clean all                         # clean all cached data

13. DEB Package Management

dpkg -i package.deb               # install or upgrade DEB package
dpkg -r package_name              # remove DEB package
dpkg -l                          # list installed DEB packages
dpkg -l | grep httpd             # filter installed DEBs containing "httpd"
dpkg -s package_name              # show information about installed package
dpkg -L package_name              # list files provided by installed DEB
dpkg --contents package.deb       # list files in an uninstalled DEB
dpkg -S /bin/ping                 # find which DEB provides a file
apt-get install package_name       # install or upgrade DEB package
apt-cdrom install package_name    # install from CD-ROM
apt-get update                    # refresh package list
apt-get upgrade                   # upgrade all installed packages
apt-get remove package_name       # remove DEB package
apt-get check                     # verify repository integrity
apt-get clean                     # clean downloaded package cache
apt-cache search searched-package # search package names

14. Network Commands (Ethernet and Wi‑Fi)

ifconfig eth0                     # show Ethernet configuration
ifup eth0                          # enable network interface
ifdown eth0                        # disable network interface
ifconfig eth0 192.168.1.1 netmask 255.255.255.0   # set static IP
ifconfig eth0 promisc              # enable promiscuous mode
dhclient eth0                      # obtain IP via DHCP
route -n                           # display routing table
route add -net 0.0.0.0/0 gw IP_Gateway          # set default gateway
route del 0.0.0.0/0 gw IP_Gateway               # delete static route
echo "1" > /proc/sys/net/ipv4/ip_forward       # enable IP forwarding
hostname show                      # display system hostname
host www.example.com               # resolve hostname to IP
nslookup www.example.com           # DNS lookup
ip link show                       # show link status of all interfaces
mii-tool eth0                      # show link status of eth0
ethtool eth0                       # show statistics of eth0
netstat -tup                       # list active network connections with PID
netstat -tupl                      # list listening services with PID
tcpdump tcp port 80                # capture HTTP traffic
iwlist scan                        # scan for wireless networks
iwconfig eth1                      # show wireless interface configuration
whois www.example.com              # query WHOIS database

15. System Information and Monitoring

date                     # show or set system date/time
hwclock                  # show hardware clock (requires root)
cal                      # display calendar
uptime                   # show system uptime
echo "text"               # display text
cat file1                # display file contents
head -n 10 file1         # show first 10 lines
tail -n 10 file1         # show last 10 lines
more file1               # paginate output (forward only)
less file1               # paginate output (forward/backward)
ls -al | more            # long format list with pagination
ls -al | less            # long format list with scrollable view
dmesg                    # kernel ring buffer messages
df -h                    # filesystem disk space usage
du -sh dir1              # estimate disk usage of dir1
free -m                  # show memory usage
ps aux                   # list running processes
top                      # interactive process viewer

16. File System Utilities

file file1                # determine file type
mount -o loop file.iso /mnt/iso   # mount ISO image
umount /mnt/iso          # unmount ISO
mkfs /dev/hda1           # create filesystem on partition
mke2fs /dev/hda1         # create ext2 filesystem
mke2fs -j /dev/hda1      # create ext3 filesystem with journaling
mkfs -t vfat -F 32 /dev/hda1   # create FAT32 filesystem
fdformat -n /dev/fd0     # format floppy disk
mkswap /dev/hda3         # create swap partition
swapon /dev/hda3         # enable swap
swapon /dev/hda2 /dev/hdb3   # enable multiple swap partitions

17. Backup and Restore

dump -0aj -f /tmp/home0.bak /home   # full backup of /home
dump -1aj -f /tmp/home0.bak /home   # interactive backup of /home
restore -if /tmp/home0.bak          # interactive restore
rsync -rogpav --delete /home /tmp   # sync directories
rsync -az -e ssh --delete /home user@host:/tmp   # rsync over SSH with compression
dd if=/dev/hda | gzip | ssh user@host "dd of=hda.gz"   # remote backup via SSH
dd if=/dev/sda of=/tmp/file1        # copy disk to file
tar -Puf backup.tar /home/user      # incremental backup
(cd /tmp/local && tar c .) | ssh user@host "cd /home/share && tar x -p"   # copy directory via SSH
find /home/user1 -name "*.txt" | xargs cp -av --target-directory=/home/backup/ --parents   # copy matching files preserving hierarchy
find /var/log -name "*.log" | tar cv --files-from=- | bzip2 > log.tar.bz2   # archive log files
dd if=/dev/hda of=/dev/fd0 bs=512 count=1   # copy MBR to floppy
dd if=/dev/fd0 of=/dev/hda bs=512 count=1   # restore MBR from floppy

18. Miscellaneous Commands

who                         # list logged‑in users
w                           # detailed user activity
dmesg                       # kernel messages
lsblk                       # list block devices
blkid                       # display block device attributes
chmod 644 file              # set standard permissions
chown user:group file       # change owner and group
ln -s target link           # create symbolic link
ln target link              # create hard link
tar cf - . | (cd /tmp/backup && tar xf -)   # copy directory preserving permissions

19. VIM Editor Basics

vim filename                # open file in VIM
:i                          # insert mode before cursor
:o                          # insert mode on new line below
:dd                         # delete current line
:yy                         # yank (copy) current line
:n yy                       # yank n lines
:p                          # paste after cursor
:u                          # undo last change
:r                          # replace character under cursor
:/pattern                   # search for pattern
:!command                   # execute external command
:sh                         # drop to shell
:set number                 # show line numbers
:w                          # write (save) file
:q                          # quit VIM
:q!                         # quit without saving
:x                          # write and quit (same as :wq)

20. Software Package Management (RPM)

rpm -ivh package.rpm                 # install
rpm -e package_name                  # erase
rpm -Uvh package.rpm                 # upgrade
rpm -Fvh package.rpm                 # freshen (upgrade if installed)
rpm -qa                              # query all installed packages
rpm -q package_name                  # query specific package
rpm -ql package_name                 # list files of installed package
rpm -qi package_name                  # detailed info
rpm -qc package_name                  # list config files
rpm -qf /path/to/file               # find which package provides a file

21. Software Package Management (DEB)

dpkg -i package.deb               # install
dpkg -r package_name              # remove
dpkg -l                           # list installed packages
apt-get install package_name      # install/upgrade via APT
apt-get remove package_name       # remove package
apt-get update                    # update package lists
apt-get upgrade                   # upgrade all packages
apt-cache search keyword          # search packages

22. Additional Tools

grep pattern file                # search for pattern in file
awk '{print $1}' file            # process text columns
sed 's/old/new/g' file           # stream editor substitution
cut -d':' -f1 /etc/passwd        # extract fields
sort file | uniq                 # unique sorted lines
tr '[:lower:]' '[:upper:]' < file # translate case
wc -l file                       # count lines
chmod 755 script.sh              # make script executable