Linux Startup Basic Commands Compilation

$ # print current working directory is used to see the current directory absolute path

$ pwd

$ # This will take you to your home directory

$ cd


$ # This will take you one directory back (space is important)
$ cd ..

$ # This will take you to the file system root
$ cd /

$ # This will take you to the directory that you specified
$ cd <dir>

$ # This will list the current working directory content.
$ ls

$ # This will give additional info such as permission, owner, group, timestamp, file name
$ ls -l

$ # This is the most used command as it sorts the file by timestamp (t) and then displays in descending order (r).
$ ls -lrt

$ # (a) Is used to display hidden contents as well
$ ls -la

$ # This is used to list directory contents without actually traversing to that location
$ ls <dir>

$ # Make directory command is used to create directories
$ mkdir <dir>

$ # used to create directory of current date, date hyphen capital i
$ mkdir $(date -I)

$ # Use rm with recursive attribute -r to remove directory
$ rm -r <dir>


$ # Use rm with force attribute to silently delete all files -rf
$ rm -rf <dir>


$ # Use this command with file name to delete it, it will ask for confirmation.
$ rm <file name>


$ # Use this command to delete file silently
$ rm -f <file name>

$ # This will list the file contents on console, used only for files with less information.
$ cat <file name>

$ # This is used to view file or perform actions such as searching its content
$ less <file name>

$ # This can be used to view file content as well
$ cat <file name>

$ # This is the simplest command used to edit file.
$ # once the editing is done user can use the control + o to save changes
$ # control + x to exit

$ nano <file name>

$ # This will move the file from current location to temp folder

$ mv file1 /tmp/

$ find <location> -n <file name>

$ find /home/test -n “dummy.text”

$ # Same as above “i” is used to ignore case when looking for the file
$ find <location> -in <file name>


$ #To search files only and ignore all errors
$ find -type f -n <file name> 2>/dev/null  


$ # To search directory only and ignore all errors
$ find -type d -n <dir name> 2>/dev/null  

$ # Search for text in a specific file
$ grep “text” file name

$ # Search for text in all file in current folder
$ grep “text” *

$ # Search for text in a specific file name pattern
$ grep “text” file_name*

$ # Search for text in multiple files
$ grep “text” <file1>

$ grep "text1\|text2" server.log

$ grep “text” <file1> <file2> <file3>

$ grep -w "text" <file>

$ grep “hello*ld” <file>

$ # Use the "." for a single character match. 
$ # If you want to get a list of all five-character English dictionary words starting with "h" and ending in "o" 
$ grep '\<h…o\>' <file>

$ # Use ‘B’ to show few lines before the search and ‘A’ to show few lines after the search
$ grep -B 3 -A 2 "started" server.log

$ # To see last few lines of a file
$ tail file_name

$ # To see contents of file as they change
$ tail -f file_name

$ # To open a file and view contents

$ # Open file and select Shift + G to see it work like tail -f command, use Control + C to stop auto rendering of changes

$ # Press “:” Colon and then use ? <text> to search text from bottom to top

$ # Press “:” Colon and then use / <text> to search text from top to bottom

$ # Use “n” to find previous occurrence and shift + n to find the next occurrence

$ less file_name

$ # To see differences in first and second files
$ diff file_1 file_2

$ # To see all running process
$ ps -ef

$ # To list specific process from the list
$ ps -ef | grep <process name>

$ # Awk is used to split the output and pull out the specific sections separated by space
$ df -h | awk '{print $2}'

$ # Tar is the most common command to create archives
$ # -c is used to create tar
$ # -v list files when creating tar
$ # -f archive file is local

$ tar -cvf test.tar <folder/file>


$ # -x is used to extract the tar
$ tar -xvf test.tar

$ # ssh is used to connect to a remote server, by default it connects to port 22
$ ssh user@server


$ # -p is used to connect to a different port

$ ssh -p 44 user@server

$ # scp is used to transfer files from local to remote 
$ # scp <file> user@server:<path>
$ # Example:

$ scp test.txt rahul.chandna@testbox:/tmp/

$ # scp can also be used to transfer files from remote to local
$ # scp user@server:<path> /tmp
$ # Example: 

$ scp rahul.chandna@testbox:/tmp/test /tmp/

$ # Use -r to transfer folders recursively from local to remote
$ # scp -r <dir> user@server:<path> 
$ # Example:

$ scp -r /tmp/test rahul.chandna@testbox:/tmp/

$ # You can use less or cat the meminfo file to see server memory stats
$ less /proc/meminfo

$ cat /proc/meminfo

$ # You can use the top command to see all running process and server memory
$ top

$ # Check this file on Red Hat box
$ less /etc/redhat-release


$ # Check this file on SUSE box
$ less /etc/SuSE-release

$ # df is used to see size of all disks
$ # -h is used to print in human readable form.

$ df -h

$ # du is used to see size of files when used with ‘s’ it calculates the   total size of folder and ‘h’ is used to print it in human readable form
$ du -sh

$ # This is used to switch to different user, this will ask for the user password
$ su - <username>


$ # If you have sudo access to run ‘su’ then you could switch to a different user using sudo and this will not ask for user password
$  sudo su - <username>

[More Examples](https://rahulchandna.com/tags/wget/)
$ # wget is an important tool to check site availability/download any http content if you have the complete URL

$ wget <URL>

$ # If you console looks cluttered, you could simply use the combination of control key and L to clear it.

$ # Cntrl key + L


$ # Same can be done by calling clear command
$ clear

$ # This command is used to generate password hash that is then used in automated user creation scripts.

$ openssl passwd -1 <string>

$ # This command is used to generate random string that could be used as a password or a user key.
$ # the last digit ‘32’ in this case is used to define the length of the generated string

$ openssl rand -base64 32