Linux Administration

All commands mentioned here reflect for Suse Linux flavor:

File Commands:
1. ls    =Directory listing
2. ls -al      =Formatted listing with hidden files
3. ls -lt      =Sorting the Formatted listing by time modification
4. cd dir    =Change directory to dir
5. cd    =Change to home directory
6. pwd     =Show current working directory
7. mkdir dir     =Creating a directory dir
8. cat >file     =Places the standard input into the file
9. more file       =Output the contents of the file
10. head file     =Output the first 10 lines of the file
11. tail file     =Output the last 10 lines of the file
12. tail -f file      =Output the contents of file as it grows,starting with the last 10 lines
13. touch file     =Create or update file
14. rm file     =Deleting the file
15. rm -r dir      =Deleting the directory
16. rm -f file        =Force to remove the file
17. rm -rf dir       =Force to remove the directory dir
18. cp file1 file2      =Copy the contents of file1 to file2
19. cp -r dir1 dir2      =Copy dir1 to dir2;create dir2 if not present
20. mv file1 file2       =Rename or move file1 to file2,if file2 is an existing directory
21. ln -s file link      =Create symbolic link link to file

Process management:
1. ps       =To display the currently working processes
2. top     =Display all running process
3. kill pid      =Kill the process with given pid
4. killall proc       =Kill all the process named proc
5. pkill pattern       =Will kill all processes matching the pattern
6. bg      =List stopped or background jobs,resume a stopped job in the background
7. fg       =Brings the most recent job to foreground
8. fg n       =Brings job n to the foreground

File permission:
1. chmod octal file      =Change the permission of file to octal,which can be found separately for user,group,world by adding,
• 4-read(r)
• 2-write(w)
• 1-execute(x)
2. chown       =Change the owner of file system files, directories


Searching:
1. grep pattern file      =Search for pattern in file
2. grep -r pattern dir      =Search recursively for pattern in dir
3. command | grep pattern       =Search pattern in the output of a command
4. locate file    =Find all instances of file
5. find . -name filename       =Searches in the current directory (represented by a period) and below it, for files and directories with names starting with filename
6. pgrep pattern       =Searches for all the named processes , that matches with the pattern and, by default, returns their ID

System Info:
1. date   =Show the current date and time
2. cal    =Show this month's calender
3. uptime       =Show current uptime
4. w     =Display who is on line
5. whoami        =Who you are logged in as
6. finger user       =Display information about user
7. uname -a      =Show kernel information
8. cat /proc/cpuinfo      =Cpu information
9. cat proc/meminfo      =Memory information
10. man command       =Show the manual for command
11. df      =Show the disk usage
12. du      =Show directory space usage
13. free      =Show memory and swap usage
14. whereis app     =Show possible locations of app
15. which app      =Show which applications will be run by default


Compression:
1. tar cf file.tar file     =Create tar named file.tar containing file
2. tar xf file.tar      =Extract the files from file.tar
3. tar czf file.tar.gz files       =Create a tar with Gzip compression
4. tar xzf file.tar.gz     =Extract a tar using Gzip
5. tar cjf file.tar.bz2      =Create tar with Bzip2 compression
6. tar xjf file.tar.bz2     =Extract a tar using Bzip2
7. gzip file      =Compresses file and renames it to file.gz
8. gzip -d file.gz      =Decompresses file.gz back to file


Network:
1. ping host      =Ping host and output results
2. whois domain        =Get whois information for domains
3. dig domain      =Get DNS information for domain
4. dig -x host      =Reverse lookup host
5. wget file    =Download file
6. wget -c file    =Continue a stopped download

Shortcuts:
1. ctrl+c    =Halts the current command
2. ctrl+z        =Stops the current command, resume with fg in the foreground or bg in the background
3. ctrl+d     =Logout the current session, similar to exit
4. ctrl+w      =Erases one word in the current line
5. ctrl+u      =Erases the whole line
6. ctrl+r      =Type to bring up a recent command
7. !!      =Repeats the last command
8. exit      =Logout the current session
9. clear      =Clears the screen

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