In Linux you can modify user accounts using this usermod command
usermod [-c comment] [-d home_dir [ -m]] [-e expire_date] [-f inactive_time] [-g initial_group] [-G group[,…]] [-l login_name] [-p passwd] [-s shell] [-u uid [ -o]] [-L|-U] login
|-c comment||The new value of the user’s password file comment field. It is normally modified using the chfn utility.|
|-d home_dir||The user’s new login directory. If the -m option is given the contents of the current home directory will be moved to the new home directory, which is created if it does not already exist.|
|-e expire_date||The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.|
|-f inactive_time||The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.|
|-g initial_group||The group name or number of the user’s new initial login group. The group name must exist. A group number must refer to an already existing group. The default group number is 1.|
|-G group[,…]||A list of supplementary groups which the user is also a member of. Each group is separated from the next by a comma, with no intervening whitespace. The groups are subject to the same restrictions as the group given with the -g option. If the user is currently a member of a group which is not listed, the user will be removed from the group.|
|-l login_name||The name of the user will be changed from login to login_name. Nothing else is changed. In particular, the user’s home directory name should probably be changed to reflect the new login name.|
|-p passwd||The encrypted password, as returned by crypt.|
|-s shell||The name of the user’s new login shell. Setting this field to blank causes the system to select the default login shell.|
|-u uid||The numerical value of the user’s ID. This value must be unique, unless the -o option is used. The value must be non-negative. Values between 0 and 99 are typically reserved for system accounts. Any files which the user owns and which are located in
the directory tree rooted at the user’s home directory will have the file user ID changed automatically. Files outside of the user’s home directory must be altered manually.
|-L||Lock a user’s password. This puts a ‘!’ in front of the encrypted password, effectively disabling the password. You can’t use this option with -p or -U.|
|-U||Unlock a user’s password. This removes the ‘!’ in front of the encrypted password. You can’t use this option with -p or -L.|
# usermod -d /home2/usr1 usr1
Create the new home Dir for usr1 in /home2 & Move old Dir contents to this Dir.
# usermod -e 2005-04-30 usr1
From 30/4/2005 the usr1 acc will be disabled.
# usermod -f 6 usr1
After passwd expires, system will allow the user to login for 6 days with a warning to change his passwd.
# usermod -g prof usr1
Set usr1′s initial group as prof.
# usermod -p $1$d8 usr1
Set the new passwd for the usr1
# usermod -s /bin/bash usr1
Set Bash as the default login shell for the usr1.
# usermod -L usr1
Lock a user’s password.
# usermod -U usr1
Unlock a user’s password.
# usermod –l user1 ser2
We use usermod -l option in the example above to change login name for aura. So the username aura has been replaced with the new name auta. If we try to login with username aura now, the system will give login incorrect error because aura is not exist in the system.
You can also put all usermod options that you want to use together in one line. Here is the example on how to do that:
# usermod –g user –d /home/aura –s /bin/csh –c sample comment –p password aura
# id aura
#usermod -a -G ibm john
Checking the groups of a user