Computer Networking Technology: Basic Linux

General Concept of Linux:-

1. Red Hat Enterprise Linux 6 officially supports 22 languages: English, Bengali, Hindi, Chinese(Simplified), Chinese(Traditional), German, French, Italian, Japanese, Korean, Tamil, Gujarati, Assamese, Kannada, Malayalam, Marathi, Oriya, Portuguese(Brazilian), Punjabi, Russian, Spanish and Telugu.

2. In Unix or Linux everything is file.

3. Linux file name supports 255 characters. Alphabet(a-z), numbers(0-9), Punctuation marks support but don't support >, ?, *, ", Tab, Space.
4. Linux Terminal = [ User_name @ Host_name Current Working Directory ] User_Symbol = [ root@localhost Desktop ]# . Where # = Root User or Super User and $ = Regular User or Standard User.

Dual Boot Sequence Change in Linux:-

STEPS: -> Enter the file manually- /boot/grub/grub.conf

-> default=0 replace with default=1 (0= Linux and 1= Other OS)

-> Timeout=5 replace with Timeout=30 If you need (It's delay at booting time or delay to select an Operating System)

Some Important Command of Linux:-

Computer Shutdown Command in Linux:-

1. poweroff -> Enter

2. init 0 -> Enter

3. shutdown -h now -> Enter (Immediately)

4. shutdown 5 -> Enter (For Maintenance- after 5 minutes)

5. shutdown 01:30 -> Enter (For Maintenance- 1:30 AM or PM)

Computer Reboot Command in Linux:-

1. reboot -> Enter

2. init 6    -> Enter

               To Help Everything in Linux:-

1. man <command>    ->    Enter (To return press q)
2. info    <command> ->    Enter (To return press q)
    4. <command>    --help               ->    Enter
5. Go to Documentation Directory    ->    /usr/share/doc

                Some Single Command of Linux:-

                        1. cal   or   cal 4 2014 -> Enter (To see calender)
2. pwd -> Enter (To see current working directory)
3. w    ->   Enter (Who Logged on currently)
4. id    -> Enter (To see User & Group ID)
5. tty -> Enter (Current Terminal Device)
6. bc    -> Enter (Basic Calculator:to back-> :quit -> Enter)
7. ls -> Enter (To see Files & Directories of current working directory)
8. ls -a -> Enter (To see Files, Directories & all hidden contents of a directory)
9. ls -al   -> Enter (To see ,, ,, & all hidden contents of a directory with permissions)
   10. ls -il -> Enter (To view the contents of a directory with their inode numbers)
   11. which <Command>    -> Enter (To know the origin/Location/path of Command)
   12. a , i , o                    ->   Enter (To go to insert mode within vim editor)
                       13. history                      ->   Enter (To see all commands of using current user)
                       14. df                             ->   Enter (To see Hard Disk information with KB)
                       15. df    -m                     ->   Enter (To see Hard Disk information with MB)
   16. df    -h                     ->   Enter (To see Hard Disk information with GB)
   17. fdisk -l    -> Enter (To see all types of Hard Disk partition information)
   18. date    -> Enter (For display date & time)

               Change Date & Time:-

                        1.date    mmddhhmimiyyyy    ->    Enter

Creating and Deleting a File:-

1. touch <file_name> -> Enter (To create a File)
                        2. rm <file_name>    -> Enter (To delete a File)

               To Edit a File:-

1. vi         <file_name> -> Enter
2. vim    <file_name> -> Enter
3. nano    <file_name> -> Enter

               Move(Cut) and Re-name a File or a Directory:-

                        1. mv    <source>       <destination>      ->    Enter (To move or cut a file or a diretory)
                        2. mv    <old_name>    <new_name>    ->    Enter (To rename a file or a directory)

               To view first & last lines of a File:-

1. head      <file_name>    -> Enter (Only First 10 lines)
2. head    -n   15    <file_name> -> Enter (Desired first lines)

3. tail          <file_name>    -> Enter (Only Last 10 lines)
4. tail    -n   14    <file_name>    -> Enter (Desired last lines)

               Copy a File or a Directory:-

                        1. cp    <source> <destination>    ->    Enter

Creating a Directory:-

1. mkdir directory_name -> Enter (A single Directory)

2. mkdir -p X/{a,b,c}/{x,y,z} -> Enter (Directory within a Directory)

Delete a Directory:-

1. rmdir directory_name -> Enter (For empty Directory)

2. rm -r directory_name -> Enter (Not empty Directory)

3. rm -rf directory_name -> Enter (Without facing any warning messages)

Directory Change:-

                          1. cd ..    -> Enter (To move one level up)
                          2. cd or cd ~       -> Enter (To move user's home directory)
                          3. cd -                  -> Enter (To move previous working directory)

                Switch User:-

                          1.   su       <user_name>       -> Enter ( Non-Login shell )
Return -> exit or ctrl+D
2.   su -    <user_name>    -> Enter ( Login shell )
Return -> logout or exit or ctrl+D

                Creating a Soft & Hard Link:-

                          1. ln -s    <source> <target> -> Enter (Softlink)
2. ln    <source> <target> -> Enter (Hardlink)

                Creating a User and a Group:-

                          1. useradd       <user_name>    -> Enter
2. groupadd     <group_name>    ->   Enter

                  Modify a User and a Group:-

      1. usermod   -L    <user_name> ->    Enter (To Lock or Disable a user account)
                             usermod   -U    <user_name> ->    Enter (To Unlock or Enable a user account)
                              or
         passwd    -l     <user_name> ->    Enter (To Lock or Disable a user account)
                             passwd    -u    <user_name>       ->    Enter (To Unlock or Enable a user account)

2. groupmod       <group_name>      ->    Enter

                  Delete a User and a Group:-

                          1. userdel    -r    <user_name>    ->    Enter (With home directory)

                  Creating a Password:-

                          1. passwd     <user_name>    ->    Enter

                  Delete a Password:-

1. passwd -d <user_name> ->    Enter

To view a File Contents:-

1. less         <file_name>    ->    Enter (To view a page)
2. more    <file_name>    ->    Enter (To view in Terminal)
                          3. cat          <file_name>    ->    Enter (To view in Terminal )

                  The Location of the Following Files:-

1. Grub file =    /etc/grub.conf or /boot/grub/grub.conf
2. Network file    =      /etc/sysconfig/network-scripts/ifcfg-ethx
3. Global Setting     =    /etc/sysconfig/network
4. Server Setting    = /etc/resolv.conf
5. Permanent Mounting    =    /etc/fstab


                   Vim Execute(ex) Mode Commands:-

    1. :w    -> Enter (Saves the files)
2. :w!       -> Enter (Saves the files forcely)
3. :q       -> Enter (quits)
4. :q!        -> Enter (quits forcely)
5. :wq -> Enter (Saves & quits)
6. :wq!    -> Enter (Saves & quits forcely)

Vim Execute(ex) Mode Commands:-

1. :w    -> Enter (Saves the files)

Linux Help Sites:

1. OStechnix

2. CentOS-7 Download