System Related Commands
These commands are used to view and manage Linux system-related information.
1. uname : Displays linux system information. With -a switch you can view all the information, with -r switch you can view kernel release information and with -o you can view OS information
2. cat /etc/redhat_release : Shows which version of redhat installed
3. uptime : Shows how long the system has been running
4. hostname : Shows system host name. With -i switch you can view the ip address of the machine and with -d you can view the domain name
5. last reboot : Shows system reboot history
6. date : Shows the current date and time. You can specify the format you want to view the date as well. As an example, by using 'date +%D' you can view the date in 'MM/DD/YY' format
7. cal : Shows the calendar of the current month. With -y switch you can view the calendar of the whole current year
8. w : Displays who is logged on and what they are doing
9. whoami : Shows current user id
10. finger user : Displays information about user
11. reboot : Reboots the system
12. shutdown : Shuts down the system
Hardware Related Commands
These commands are used to view and manage hardware-related aspects of the Linux machine.
13. dmesg : Displays all the messages from Kernel ring buffer. With -k switch you can view kernel messages and with -u you can view userspace messages
14. cat /proc/cpuinfo : Displays information about processes and CPUs of the system
15. cat /proc/meminfo : Displays details on hardware memory
16. cat /proc/interrupts : Lists the number of interrupts per CPU per I/O device
17. lshw : Displays information on hardware configuration of the system. But this command must be run as super user or it will only report partial information
18. lsblk : Displays block device related information of the machine. With -a you can view all block devices
19. free -m : Shows used and free memory (-m for MB)
20. lspci -tv : Shows information on PCI buses devices
21. lsusb -tv : Shows information on USB devices
22. dmidecode : Shows hardware info from the BIOS (vendor details)
23. hdparm -i /dev/sda : Shows info about disk sda
hdparm -tT /dev/sda : Performs a read speed test on disk sda
24. badblocks -s /dev/sda : Tests for unreadable blocks on disk sda
Statistic Related Commands
These set of commands are used to view various kinds of stats of the Linux system
25. mpstat 1 : Displays processors related statistics
26. vmstat 2 : Displays virtual memory statistics
27. iostat 2 : Displays I/O statistics
28. tail -n 500 /var/log/messages : Displays the last 500 kernel/syslog messages
29. tcpdump -i eth1 : Captures all packets flow on interface eth1. With -w switch you can specify a file where you can direct the output to
tcpdump -i eth0 'port 80' : Monitors all traffic on port 80 on interface eth0
30. lsof : Lists all open files belonging to all active processes
lsof -u testuser : Lists files opened by a specific user
31. free -m : Shows RAM memory details
32. watch df -h : Watches changeable disk usage continuously
User-Related Commands
These commands are used to manage Linux users
33. id : Shows the active user and group information. With -G switch you can view the IDs of groups
34. last : Shows a list of last logins on the system. Using -a switch you can add the hostname to the last column of the output
35. who : Shows who is logged on the system
36. groupadd admin : Adds the group "admin"
37. useradd -c "Sam Tomshi" -g admin -m sam : Creates user "sam" and adds to group "admin"
38. userdel sam : Deletes user sam
39. adduser sam : Adds user "sam"
40. usermod : Modifies user information
41. passwd user1 : Changes the password of user1
File Related Commands
These commands are used to handle files and directories
42. ls -al : Displays all information about files/directories. This includes displaying all hidden files as well
43. pwd : Shows current directory path
44. mkdir directory-name : Creates a directory
45. rm file-name : Deletes file
rm -r directory-name : Deletes directory recursively
rm -f file-name : Forcefully removes file
rm -rf directory-name : Forcefully removes directory recursively
46. cp file1 file2 : Copies linux files, here file1 to file2
cp -r dir1 dir2 : Copies dir1 to dir2, creates dir2 if it doesn't exist
47. mv file1 file2 : Moves files from one place to another/renames file1 to file2
48. ln -s /path/to/target-directory-name link-dir : Creates a symbolic link to link-dir
49. touch file : Creates empty file
50. cat file : Prints the file content in terminal
51. more file : Display the contents of file
52. head file : Display the first 10 lines of file
53. tail file : Outputs the last 10 lines of file
tail -f file : Outputs the contents of file as it grows starting with the last 10 lines
54. gpg -c file : Encrypts file
gpg file.gpg : Decrypts file
55. cksum file : View the checksum of the file
56. diff file1 file2 : View the differences between contents of file1 and file2
57. ln -s target-file link-file : Create a soft link named link-file to target-file
58. sort : Sorts files in alphabetical order
59. uniq : Compares adjacent lines in a file and removes/reports any duplicate lines
60. wc : Counts number of words/lines
61. dir : Lists the content of the directory
62. tee : Command for chaining and redirection
63. tr : Command for translating characters
Process Related Commands
These commands are used to handle Linux processes
64. ps : Displays your currently active processes
ps aux | grep 'telnet' : Displays all process ids related to telnet process
65. pmap : Display Memory map of process
66. top : Display all running processes and cpu/memory usage
67. kill pid : Kills process with mentioned pid
68. killall proc : Kills all processes named proc
69. pkill processname : Sends kill signal to a process with its name
70. bg : Resumes suspended jobs without bringing them to foreground
71. fg : Brings the most recent job to foreground
fg n : Brings job n to the foreground
File Permission Related Commands
These commands are used to change permissions of the files
72. chmod octal file-name : Changes the permissions of file to octal
chmod 777 /data/test.c : Sets rwx permission for owner , group and others
chmod 755 /data/test.c : Sets rwx permission for owner and rx for group and others
73. chown owner-user file : Changes owner of the file
chown owner-user:owner-group file-name : Changes owner and group owner of the file
chown owner-user:owner-group directory : Changes owner and group owner of the directory
74. chgrp group1 file : Changes the group ownership of the file to group1
Network Related Commands
These commands are used to view and edit network configurations related aspects of the system
75. ifconfig -a : Displays all network interface and set ip address
76. ifconfig eth0 : Displays eth0 ethernet port ip address and details
77. ip addr show : Display all network interfaces and ip addresses
78. ip address add 192.168.0.1 dev eth0 : Sets ip address of eth0 device
79. ethtool eth0 : Linux tool to show ethernet status
80. mii-tool eth0 : Linux tool to show eth0 status
81. ping host : Sends echo requests to the host to test ipv4 connection
82. whois domain : Gets who is information for domain
83. dig domain : Gets DNS nameserver information for domain
dig -x host : Reverse lookup host
84. host google.com : Lookup DNS ip address for the name
85. hostname -i : Lookup local ip address
86. wget file : Downloads file
87. netstat -tupl : Lists all active listening ports
88. nslookup : Resolves domain names to IP addresses
Compression / Archive Related Commands
These commands are used to compress and decompress files
89. tar cf home.tar home : Creates a tar named home.tar containing home/
tar xf file.tar : Extracts the files from file.tar
tar czf file.tar.gz files : Creates a tar with gzip compression
90. gzip file : Compresses file and renames it to file.gz
91. bzip2 -z file : Compresses file and renames it to file.bz2
bzip2 -d file.bz2 : Decompress the file
Package Installation Related Commands
These commands are used to manage Linux packages
92. rpm -i pkgname.rpm : Installs rpm based package
rpm -e pkgname : Removes package
93. make : Install from source file
Search Related Commands
These commands are used to search for files and patterns
94. grep pattern files : Searches for pattern in files
grep -r pattern dir : Searches recursively for pattern in dir
95. locate file : Finds all instances of file
96. find /home/tom -name 'index*' : Finds file names that start with "index" inside /home/tom directory
find /home -size +10000k : Finds files larger than 10000k in /home
Login Related Commands
These commands are used to log into another host
97. ssh user@host : Securely connect to a host as user
ssh -p port $ user@host : Connects to host using specific port
98. telnet host : Connects to the system using telnet port
File Transfer Related Commands
These commands are used to copy files from one system to another system
99. scp file.txt server2:/tmp : Secure copy file.txt to remote host /tmp folder
scp nixsavy@server2:/www/*.html /www/tmp : Copies *.html files from remote host to current host /www/tmp folder
scp -r nixsavy@server2:/www /www/tmp : Copies all files and folders recursively from remote server to the current system /www/tmp folder
100. rsync -a /home/apps /backup/ : Synchronizes source to destination
rsync -avz /home/apps $ linoxide@192.168.10.1:/backup : Synchronize files/directories between the local and remote system with compression enabled
Disk Usage Related Commands
These commands are used to view disk statistics
101. df -h : Shows free space on mounted filesystems
df -i : Shows free inodes on mounted filesystems
102. fdisk -l : Shows disks partitions sizes and types
103. du -ah : Displays disk usage in human readable form
du -sh : Displays total disk usage on the current directory
104. findmnt : Displays target mount point for all filesystems
105. mount device-path mount-point : Mounts a device to the device-path
Directory Traverse Related Commands
These commands are used to change the directory
106. cd .. : Goes up one level of the directory tree
cd : Goes to $HOME directory
cd /test : Changes to /test directory
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