The options which apply to the usermod command are:
The new value of the user’s password file comment field. It is
normally modified using the chfn(1)
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.
The date on which the user account will be disabled. The date is
specified in the format YYYY-MM-DD.
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.
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.
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. This behaviour can be changed
via -a option, which appends user to the current supplementary
The name of the user will be changed from LOGIN to NEW_LOGIN.
Nothing else is changed. In particular, the user’s home
directory name should probably be changed to reflect the new
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.
When used with the -u option, this option allows to change the
user ID to a non-unique value.
The name of the user’s new login shell. Setting this field to
blank causes the system to select the default login shell.
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 999 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.
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 will not allow you to change the name of a user who is logged
in. You must make certain that the named user is not executing any
processes when this command is being executed if the user’s numerical
user ID is being changed. You must change the owner of any crontab
files manually. You must change the owner of any at jobs manually. You
must make any changes involving NIS on the NIS server.