How to Upgrade RHEL Linux ....

Basic Linux Commands used daily

Navigation :

1. To print working directory :  pwd
2. To change directory            :  cd
3. To list files and contents of directories :  ls
4. To list files/direc in long format : ls –l
5. To list the hidden files/direc : ls –a
6. To view text files : less  text_file
7. To know what kind of a file it is : file name_of_file

Manipulating Files:

8. To Copy files and directories :   cp file1 filenew
9. To move or rename the files/directories : mv  file1  filenew
10. To remove the file/directories :   rm file
11. To make directory : mkdir

Working with commands:

12. Display Information about command type: type  command(ls,cp..etc)
13.  To locate the command : which command (ls…etc)
14. To display the reference page: help –m  command(cd..etc)
15. To display on-line command interface : man ls

I/O Redirection :

16. To redirect standard output to a file   : “ > “    ( ls  >  file_list.txt )
17. To redirect standard output to a file   : “ < ”    (sort <  file_list.txt > sorted_file.txt)
18. With pipeline the output of one command is fed into input of another :

             ls –l | less   

  rpm –qa| grep –i filename :   Rpm –qa  list  for all rpm files installed on system and  Grep Accweb  it  find any containing the string “accweb” and output them.

19. Filters:

sort : Sorts standard input then outputs the sorted result on standard output.

grep : Examines each line of data it receives from standard input and outputs every line that contains a specified pattern of characters.

tail : Outputs the last few lines of its input. (Ex : tail –f logs.txt)

Permissions:

20. to change the permissions of folders/files : Chmod  XXX filename
21. Temporarily become super user : su & sudo
22. Change file ownership of user :  chown  user filename
23. Change file ownership of group : chgrp  group filename
24. Change file ownership of user & group : chown  user:group filename

Job Control:

25. To know the process running  : ps  or jobs
26. to know the processes running on system   : Ps  aux
27. to find process with user  :           Ps  –u  name of User
28. to kill the process   : Kill -9  process name

 -9   Kill signal

-1   hang-up signal

-2 interrupt signal

-15 termination signal

Wildcards:

29. Matches any characters  :  *
30. Matches ant single character:  ?
31. All filenames  :  *
32. All filenames that begin with the character "g" :  g*
33. All filenames that begin with the character "b" and end with the characters ".txt" : b*.txt

Txt Editor:

34.  to edit the configuration/txt  file (command line)  : vi/vim 
35.  gedit is the editor supplied  (GUI)  : gedit

Searching:

36. Search  file by name  : Find -name "query"
37. Search file by type   : Find  -type  type_descriptor_query

                 Type decriptor :

F -  regular file

d- directory

I -symbolic link

38. Search  :  locate filename
39. We can use  locate/grep for searching :

grep  "codes"  install.log   : searh for word/string/line  in a file   (grep –n ,display with line number, grep –I it search for case sensitive )

grep -i  "codes"(Search string)   /root/install.log (path of file)

[root@localhost ~]# grep "codes" install.log

Installing iso-codes-3.16-2.el6.noarch

Remote Administration :

40. Can use ssh with a full hostname to connect to a remote machine : ssh hostname
41. Connect to a remote system with your current username :ssh username@hostname
42. Allows you to copy files from one computer/server to another computer/server : scp

Other Commands:

43. To know which user is logged : whoami
44. To know who recently  logged : users
45.  
46. history : for monitoring commands executed by user.
47.    Service :  for  start/stop/restart/status (Service httpd start,service red5 stop,…etc)
48. Top : to monitor system activities
49. df    - to know disk file space on machine (df –h  size in GB,df –m  sizein MB )
50. fdisk –l  - to  display with partitions
51. Netstat : give information about network connections (nestat –tcp  display all tcp connections)
52. Mount – for mounting formatted partitions

Basic Network Commands :   

53. Netstat :   to look up the various active connections within a computer
54. Traceroute : to know the number hop it travelled to reach destination.
55. Nslookup:   It is use for DNS quiery.

56. Dig : It is use for DNS quiery.It display full info.

57. Ifconfig  :  It is very useful in determining what could be wrong with a network.to know IP address.
58. Ifup:  enable interface
59. Ifdown : disable interface.
60. Ping :  PING is used to check for a response from another computer on the network.
61. Ping  -c  hostadress :
62.  

What command used to check Disk Space ?

1 Command to know disk space  :  df                

2 Command to know size in GB  :  df -h

3 Command to know size in MB  : df -m

How to change the Ownership of file/Group?

ls -lart tmpfile
-rw-r--r-- 1 himanshu family 0 2012-05-22 20:03 tmpfile

Before using command :

Command to change Ownership of file:  chown  root  tmpfile

Command to change Ownership of group : chgrp  friends tmpfile

After using command above:

ls -l tmpfile
-rw-r--r-- 1 root friends 0 2012-05-22 20:03 tmpfile

What command used for finding the process running?

Command to see processes running   :  ps

Command to find the process run by user :  ps -u  Sukesh

What  Command to kill a process ?

                            Kill -9    process name

-9   Kill signal

-1   hangup signal

-2  interrupt signal

-15  termination signal

Search for a file by name ?

Find -name "query"

Search the file by type?

Find -type type_descriptor query

Type decriptor :

F -  regular file

d- directory

I -symbolic link

How  to know which user is logged?

Command :   whoami

Who recently  logged in?

Command  : users

How do we transfer file from one server to another?

          Command used  to establish ssh connection :   ssh  username@ IP

How we move file from one folder to another?

                            Command :       Mv   file name   remote folder path

How do we copy file from one folder to another folder?

                            Command:      cp  filename  remote folder path

What command use for add interface?

                  Command :            ifup

What command used fo remove interface?

                  Command :      ifdown

To know Current working Directory ?

Command used  : Pwd

Command to give permissions?

Chmod XXX  filename

777   rwx rwx rwx

rwx = 111 in binary = 7
rw- = 110 in binary = 6
r-x = 101 in binary = 5
r-- = 100 in binary = 4

Chmod 777 filename