Tuesday, May 17, 2011

User Administration

User Administration is the most important part of System Administration in LINUX.
User creation,modification,deletion are major parts in User Administration.
useradd    :    User creation
passwd       :  Give password for user aftre creation
userdel     :    User deletion
userdel -rf     :  Forcibly remove user and its related home directory and files.
usermod        :   to modify the user data.
Options include  —-   -u: to change UserID (UID),   -g: to change GroupID (GID),  -d: to change Home Directory,  -s: to change the shell,  -c: to change or assign a  comment,  -L: to lock user account,  -U: to unlock the user account,  -l: to remove the user account,  -o: to overrite/duplicate the User or Group ID.
SU  –     —-Switch User from other user.
The UID starts for a manually created User is 500.
/etc/passwd :  Contains all user information
/etd/shadow : Contains all Password information
/etc/group : Contains all the groups information
Whena user is created LINUX assumes it as mail user and the mailbox of the user is stored in /spool/mail.
Home Directory of the user is stored in /home
When a user is created some default skeleton files are created in the directory called /etc/skel. The following are the hidden files created :
.bash_profile,  .bash_logout, .bashrc, .emacs, .gtkrc
The default shell for a user is Bash and the prompt will be ‘$’ .
The prompt for Root is ‘#’.
A user created can be a member of one or more groups.
Maximum number of users created in LINUX OS are 60,000.
The kernel supports upto 1.6 million user and group accounts.
0-499 are reserved for System accounts.
500-60000 are General purpose users.