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Commands
System
| | Command |
| Display linux system information | uname -a |
| Display kernel release information | uname -r |
| Show how long a system has been running | uptime |
Archiving / Compression
| | Command |
| Create a tar file containing a directory | tar cf home.tar /home |
| Create a tar file with gzip compression | tar czf tarfile.tar.gz files |
| Extract files from a tar file | tar xf filename.tar |
| Compress file and rename it to filename.gz | gzip filename |
Booting
| | Command |
| Show boot messages | dmesg |
| Show system reboot history | last reboot |
Date and Time
| | Command |
| Show current date and time | date |
File and Disk
| | Command |
| Display all information on files and directories | ls -a |
| Show path of current directory | pwd |
| Create a directory | mkdir dirname |
| Delete a file | rm filename |
| Delete a directory recursively | rm -r dirname |
| Forcefully delete a file | rm -f filename |
| Forcefully delete a directory recursively | rm -rf dirname |
| Copy file1 to file2 | cp file1 file2 |
| Copy directory1 to directory2, create directory2 if it does not exist | cp -r dirname1 dirname2 |
| Create a symbolic link to a filename | ln -s /path/to/filename linkname |
| Create or update a file | touch filename |
| Place standard input into a file | cat > filename |
| Output contents of file | more file |
| Output first 10 lines of file | head file |
| Output last 10 lines of file | tail file |
| Output contents of file as it grows starting with last 10 lines | tail -f filename |
| Encrypt file | gpg -c filename |
| Decrypt file | gpg filename.gpg |
| Print the number of chars, words and lines in a file | wc filename |
| Execute command lines from standard input | xargs |
| Change permission of a file | chmod 666 filename |
Disk Usage
| | Command |
| Show free space on mounted filesystems | df -h |
| Show free inodes on mounted filesystems | df -i |
| Show disk partition sizes and types | fdisk -l |
| Display disk usage | du -ah |
| Display total disk usage on the current directory | du -sh |
| Display mount points for all filesystems | findmnt |
| Mount a device | mount device-path mount-point |
File Transfer
| | Command |
| Secure copy file to host | scp file.txt server2:/tmp |
| Synchronize source to destination | rsync -a /home/peter /backup/ |
Hardware
| | Command |
| Display CPU information | cat /proc/cpuinfo |
| List the number of interupts per CPU per I/O device | cat /proc/interrupts |
| List hardware configuration information | lshw |
| Display block device related information | lsblk |
| Display PCI devices | lspci -tv |
| Show USB devices | lsusb -tv |
| Show BIOS information | dmidecode |
| Show disk information | hdparm -i /dev/sda |
| Perform a disk speed test | hdparm -tT /dev/sda |
| Test for unreadable blocks on a disk | badblocks -s /dev/sda |
Login
| | Command |
| Connect to host as user | ssh user@host |
| Connect to host using specific port | ssh -p port user@host |
| Connect to host using telnet port | telnet host |
Memory
| | Command |
| Display used and free memory | free -m |
Network
| | Command |
| Show the system hostname | hostname |
| Display IP address of the host | hostname -i |
| Display all network interfaces and IP addresses | ip addr show |
| Display network interfaces and IP addresses for an interface | ip addr show eth0 |
| Set IP address | ip addr add 192.168.0.1 dev eth0 |
| Delete IP address | ip addr del 192.168.0.193/24 dev wlan0 |
| Show Ethernet status | ethtool eth0 |
| Show Ethernet status | mii-tool eth0 |
| Show Routing table | ip route show |
| Show the route packets will take | ip route get 192.168.0.1 |
| Change default route | ip route add default via 192.168.0.2 |
| Send echo request to test connection | ping host |
| Get who is information for the domain | whois domain |
| Get DNS information for the domain | dig domain |
| Get Reverse DNS information for the host | dig -x host |
| Lookup DNS IP address for the domain | host google.com |
| Lookup local IP address | hostname -i |
| Download a file | wget filename |
| Show all listening network ports | netstat -tulpn |
| Show network stats | ip -s link |
| Show network stats for an interface | ip -s -s link ls eth0 |
| Show arp entries | ip neighbour |
| Monitor network messages | ip monitor all |
| Activate network interface | ip link set ppp0 up |
| Deactivate network interface | ip link set ppp0 down |
| Enable TCP Delayed Ack | ip route quickack |
Packages
| | Command |
| Install RPM based package | rpm -i pkgname.rpm |
| Remove package | rpm -e pgkname |
| Install from source | ./configure
make
make install |
Process
| | Command |
| Display your currently active processes | ps |
| Find all processes related to “telnet” | ps aef|grep 'telnet' |
| Memory map of process | pmap |
| Display all running processes | top |
| Kill process with specific pid id | kill id |
| Kill all processes named xxx | kill xxx |
| Resumes suspended job without bringing them to the foreground | bg |
| Brings the most recent job to the foreground | fg |
| Bring job n to the foreground | fg n |
Search
| | Command |
| Search for a pattern in files | grep pattern files |
| Search recursively for pattern in directory | grep -r pattern directory |
| Find all instances of file | locate filename |
| Find filenames that start with xxx | find /home/peter -name 'xxx*' |
| Find filesnames larger than 10000k | find /home/peter -size +10000k |
Users
| | Command |
| Display who is logged in | w |
| Show who is logged into the system | who |
| Display who you are logged in as | whoami |
| Display information on a user | finger user |
| Show the active user id with login and group | id |
| Show last logins on the system | last |
| Add a group | groupadd groupname |
| Add a user | adduser peter |
| Add a user | useradd -c “Peter Roux” - g admin -m peter # Add user peter |
| Delete a user | userdel peter |
| Modify user information | usermod peter |
