usermod [options] LOGIN

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

-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.