Provided by: passwd_18.104.22.168+svn3283-3ubuntu5_amd64
usermod - modify a user account
usermod [options] LOGIN
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: -a, --append Add the user to the supplementary group(s). Use only with the -G option. -c, --comment COMMENT The new value of the user's password file comment field. It is normally modified using the chfn(1) utility. -d, --home 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, --expiredate EXPIRE_DATE The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD. -f, --inactive INACTIVE 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. -g, --gid GROUP The group name or number of the user's new initial login group. The group must exist. Any file from the user's home directory owned by the previous primary group of the user will be owned by this new group. The group ownership of files outside of the user's home directory must be fixed manually. -G, --groups GROUP1[,GROUP2,...[,GROUPN]]] 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 the -a option, which appends the user to the current supplementary group list. -l, --login NEW_LOGIN 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 manually to reflect the new login name. -L, --lock 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. Note: if you wish to lock the account (not only access with a password), you should also set the EXPIRE_DATE to 1. -m, --move-home Move the content of the user's home directory to the new location. This option is only valid in combination with the -d (or --home) option. usermod will try to adapt the ownership of the files and to copy the modes, ACL and extended attributes, but manual changes might be needed afterwards. -o, --non-unique When used with the -u option, this option allows to change the user ID to a non-unique value. -p, --password PASSWORD The encrypted password, as returned by crypt(3). Note: This option is not recommended because the password (or encrypted password) will be visible by users listing the processes. The password will be written in the local /etc/passwd or /etc/shadow file. This might differ from the password database configured in your PAM configuration. You should make sure the password respects the system's password policy. -s, --shell 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 UID The new 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. The user's mailbox, and any files which the user owns and which are located in the user's home directory will have the file user ID changed automatically. The ownership of files outside of the user's home directory must be fixed manually. -U, --unlock Unlock a user's password. This removes the '!' in front of the encrypted password. You can't use this option with -p or -L. Note: if you wish to unlock the account (not only access with a password), you should also set the EXPIRE_DATE (for example to 99999, or to the EXPIRE value from /etc/default/useradd). -Z, --selinux-user SEUSER The SELinux user for the user's login. The default is to leave this field the blank, which causes the system to select the default SELinux user.
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, the user's name, or the user's home directory is being changed. usermod checks this on Linux, but only check if the user is logged in according to utmp on other architectures. You must change the owner of any crontab files or at jobs manually. You must make any changes involving NIS on the NIS server.
The following configuration variables in /etc/login.defs change the behavior of this tool: MAIL_DIR (string) The mail spool directory. This is needed to manipulate the mailbox when its corresponding user account is modified or deleted. If not specified, a compile-time default is used. MAIL_FILE (string) Defines the location of the users mail spool files relatively to their home directory. The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and userdel to create, move, or delete the user's mail spool. MAX_MEMBERS_PER_GROUP (number) Maximum members per group entry. When the maximum is reached, a new group entry (line) is started in /etc/group (with the same name, same password, and same GID). The default value is 0, meaning that there are no limits in the number of members in a group. This feature (split group) permits to limit the length of lines in the group file. This is useful to make sure that lines for NIS groups are not larger than 1024 characters. If you need to enforce such limit, you can use 25. Note: split groups may not be supported by all tools (even in the Shadow toolsuite). You should not use this variable unless you really need it.
/etc/group Group account information. /etc/gshadow Secure group account information. /etc/passwd User account information. /etc/shadow Secure user account information.