usermod (Linux command)

Name

 * - Modify a user account

Synopsis

 * login

Description
The usermod  command modifies the system account files to reflect the changes that  are  specified  on  the  command line. The options which apply to the usermod command are


 * -c comment 
 * The new  value of the user's password file comment field.  It is normally modified using  the  chfn(1) 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_days 
 * 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
 * Addendum: groups are separated by commas without spaces, e.g. "-G group1,group2,group3". --Woozle
 * -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(3).
 * -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.
 *  login  is the username whose parameters are to be changed.

Caveats
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.

Files

 * /etc/passwd - user account information
 * /etc/shadow - secure user account information
 * /etc/group - group information

Author
Julianne Frances Haugh (jfh@austin.ibm)

Examples
The "/usr/sbin/" prefix may or may not be necessary depending on how your Linux distro is set up.
 * /usr/sbin/ -G group1, group2 , group3 username
 * Joins user username to groups group1, group2 , and group3 , and unjoins from any other groups (get list of existing groups with " username "). Group s may be identified by name or by ID; see /etc/group for list of groups and IDs.
 * this doesn't seem to work -- usermod returns a quick guide to proper usage --Woozle 01:16, 20 June 2010 (UTC)
 * -G groupname -a username
 * Adds user username to group groupname without removing user from any other groups.

Edit Log

 * 2005-06-12 Transcribed from manpage in Red Hat 7