Linux Commands Cheat Sheet
1. SYSTEM
# uname –a # Display linux system information
# uname –r # Display kernel release information
# cat /etc/redhat_release # Show which version of redhat installed
# uptime # Show how long the system has been running +
load
# hostname # Show system host name
# hostname -i # Display the IP address of the host
# last reboot # Show system reboot history
# date # Show the current date and time
# cal # Show this month calendar
# w # Display who is online
# whoami # Who you are logged in as
# finger user # Display information about user
2. HARDWARE
# dmesg # Detected hardware and boot messages
# cat /proc/cpuinfo # CPU model
# cat /proc/meminfo # Hardware memory
# free -m # Used and free memory (-m for MB)
# lspci -tv # Show PCI devices
# lsusb -tv # Show USB devices
# lshal # Show a list of all devices with their
properties
# dmidecode # Show DMI/SMBIOS: hw info from the BIOS
# hdparm -i /dev/sda # Show info about disk sda
# hdparm -tT /dev/sda # Do a read speed test on disk sda
# badblocks -s /dev/sda # Test for unreadable blocks on disk sda
3. STATISTICS
# top # Display and update the top cpu processes
# mpstat 1 # Display processors related statistics
# vmstat 2 # Display virtual memory statistics
# iostat 2 # Display I/O statistics (2sec Intervals)
# tail -n 500 /var/log/messages # Last 10 kernel/syslog messages
# tcpdump -i eth1 # Capture all packets flows on interface eth1
# tcpdump -i eth0 'port 80' # Monitor all traffic on port 80 ( HTTP )
# lsof # List all open files belonging to all active
processes.
# lsof -u testuser # List files opened by specific user
# free –m # Show amount of RAM
# watch df –h # Watch changeable data continuously
4. USERS
# id # Show the active user id with login and
group
# last # Show last logins on the system
# who # Show who is logged on the system
# groupadd admin # Add group "admin"
# useradd -c "Sam Tomshi" -g admin -m sam # Create user "sam" and add to group
"admin"
# userdel sam # Delete user sam
# adduser sam # Add user "sam"
# usermod # Modify user information
5. FILE COMMANDS
# ls –al # Display all information about files/
directories
# pwd # Show the path of current directory
# mkdir directory-name # Create a directory
# rm file-name # Delete file
# rm -r directory-name # Delete directory recursively
# rm -f file-name # Forcefully remove file
# rm -rf directory-name # Forcefully remove directory recursively
# cp file1 file2 # Copy file1 to file2
# cp -r dir1 dir2 # Copy dir1 to dir2, create dir2 if it
doesn’t exist
# mv file1 file2 # Rename or move file1 to file2. If file2
is an existing directory , move file1 into directory file2
# ln –s /path/to/file-name link-name # Create symbolic link to file-name
# touch file # Create or update file
# cat > file # Place 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
# gpg -c file # Encrypt file
# gpg file.gpg # Decrypt file
6. PROCESS RELATED
# ps # Display your currently active processes
# ps aux | grep 'telnet' # Find all process id related to telnet process
# pmap # Memory map of process
# top # Display all running processes
# kill pid # Kill process with mentioned pid id
# killall proc # Kill all processes named proc
# bg # Lists stopped or background jobs
# fg # Brings the most recent job to foreground
# fg n # Brings job n to the foreground
7. FILE PERMISSION RELATED
# chmod octal file-name # Change the permissions of file to octal , which can
be found separately for user, group and world
octal value
4 - read
2 – write
1 – execute
Example
# chmod 777 /data/test.c # Shows rwx permission for owner , rwx
permission for group, rwx permission for world
# chmod 755 /data/test.c # Shows rwx permission for owner,rw for
group and world
# chown owner-user file # Change owner of the file
# chown owner-user:owner-group file-name # Change owner and group owner of the
file
# chown owner-user:owner-group directory # Change owner and group owner of the
directory
Example
# chown bobbin:expertslogin test.txt
# ls -l test.txt
-rw-r--r-- 1 bobbin expertslogin 0 Mar 04 08:56 test.txt
8. NETWORK
# ifconfig –a # Display all network ports and ip address
# ifconfig eth0 # Display specific ethernet port ip address and
details
# ethtool eth0 # Linux tool to show ethernet status
# mii-tool eth0 # Linux tool to show ethernet status
# ping host # Send echo request to test connection
# whois domain # Get who is information for domain
# dig domain # Get DNS information for domain
# dig -x host # Reverse lookup host
# host google.com # Lookup DNS ip address for the name
# hostname –i # Lookup local ip address
# wget file # Download file
# netstat -tupl # List active connections to / from system
9. COMPRESSION / ARCHIVES
# tar cf home.tar home # Create tar named home.tar containing home/
# tar xf file.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
# gzip file # Compress file and renames it to file.gz
10. INSTALL PACKAGE
# rpm -i pkgname.rpm # Install rpm based package
# rpm -e pkgname # Remove package
Install from source
./configure
make
make install
11. SEARCH
# grep pattern files # Search for pattern in files
#grep -r pattern dir # Search recursively for pattern in dir
# locate file # Find all instances of file
# find /home/tom -name 'index*' # Find files names that start with "index"
# find /home -size +10000k # Find files larger than 10000k in /home
12. LOGIN (SSH AND TELNET)
# ssh user@host # Connect to host as user
# ssh -p port user@host # Connect to host using specific port
# telnet host # Connect to the system using telnet port
13. FILE TRANSFER
scp
# scp file.txt server2:/tmp # Secure copy file.txt to remote
host /tmp folder
# scp nixsavy@server2:/www/*.html /www/tmp # Copy *.html files from remote
host to current system /www/tmp folder
# scp -r nixsavy@server2:/www /www/tmp # Copy all files and folders
recursively from remote server to the current system /www/tmp folder
rsync
# rsync -a /home/apps /backup/ # Synchronize source to
destination
# rsync -avz /home/apps expertslogin@192.168.10.1:/backup # Synchronize
files/directories between the local and remote system with compression enabled
14. DISK USAGE
# df –h # Show free space on mounted filesystems
# df -i # Show free inodes on mounted filesystems
# fdisk -l # Show disks partitions sizes and types (run as
root)
# du -ah # Display disk usage in human readable form
# du -sh # Display total disk usage on the current
directory
15. DIRECTORY TRAVERSE
# cd .. # To go up one level of the directory tree
# cd # Go to $HOME directory
# cd /test # Change to /test directory
