path: root/man/man8/usermod.8

'\" t
.\"     Title: usermod
.\"    Author: Julianne Frances Haugh
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 11/08/2022
.\"    Manual: System Management Commands
.\"    Source: shadow-utils 4.13
.\"  Language: English
.\"
.TH "USERMOD" "8" "11/08/2022" "shadow\-utils 4\&.13" "System Management Commands"
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.SH "NAME"
usermod \- modify a user account
.SH "SYNOPSIS"
.HP \w'\fBusermod\fR\ 'u
\fBusermod\fR [\fIoptions\fR] \fILOGIN\fR
.SH "DESCRIPTION"
.PP
The
\fBusermod\fR
command modifies the system account files\&.
.SH "OPTIONS"
.PP
The options which apply to the
\fBusermod\fR
command are:
.PP
\fB\-a\fR, \fB\-\-append\fR
.RS 4
Add the user to the supplementary group(s)\&. Use only with the
\fB\-G\fR
option\&.
.RE
.PP
\fB\-b\fR, \fB\-\-badname\fR
.RS 4
Allow names that do not conform to standards\&.
.RE
.PP
\fB\-c\fR, \fB\-\-comment\fR\ \&\fICOMMENT\fR
.RS 4
update the comment field of the user in
/etc/passwd, which is normally modified using the
\fBchfn\fR(1)
utility\&.
.RE
.PP
\fB\-d\fR, \fB\-\-home\fR\ \&\fIHOME_DIR\fR
.RS 4
The user\*(Aqs new login directory\&.
.sp
If the
\fB\-m\fR
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\&. If the current home directory does not exist the new home directory will not be created\&.
.RE
.PP
\fB\-e\fR, \fB\-\-expiredate\fR\ \&\fIEXPIRE_DATE\fR
.RS 4
The date on which the user account will be disabled\&. The date is specified in the format
\fIYYYY\-MM\-DD\fR\&. Integers as input are interpreted as days after 1970\-01\-01\&.
.sp
An input of \-1 or an empty string will blank the account expiration field in the shadow password file\&. The account will remain available with no date limit\&.
.sp
This option requires a
/etc/shadow
file\&. A
/etc/shadow
entry will be created if there were none\&.
.RE
.PP
\fB\-f\fR, \fB\-\-inactive\fR\ \&\fIINACTIVE\fR
.RS 4
defines the number of days after the password exceeded its maximum age during which the user may still login by immediately replacing the password\&. This grace period before the account becomes inactive is stored in the shadow password file\&. An input of 0 will disable an expired password with no delay\&. An input of \-1 will blank the respective field in the shadow password file\&. See
\fBshadow\fR(5)
for more information\&.
.sp
This option requires a
/etc/shadow
file\&. A
/etc/shadow
entry will be created if there were none\&.
.RE
.PP
\fB\-g\fR, \fB\-\-gid\fR\ \&\fIGROUP\fR
.RS 4
The name or numerical ID of the user\*(Aqs new primary group\&. The group must exist\&.
.sp
Any file from the user\*(Aqs home directory owned by the previous primary group of the user will be owned by this new group\&.
.sp
The group ownership of files outside of the user\*(Aqs home directory must be fixed manually\&.
.sp
The change of the group ownership of files inside of the user\*(Aqs home directory is also not done if the home dir owner uid is different from the current or new user id\&. This is a safety measure for special home directories such as
/\&.
.RE
.PP
\fB\-G\fR, \fB\-\-groups\fR\ \&\fIGROUP1\fR[\fI,GROUP2,\&.\&.\&.\fR[\fI,GROUPN\fR]]]
.RS 4
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 must exist\&.
.sp
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
\fB\-a\fR
option, which appends the user to the current supplementary group list\&.
.RE
.PP
\fB\-l\fR, \fB\-\-login\fR\ \&\fINEW_LOGIN\fR
.RS 4
The name of the user will be changed from
\fILOGIN\fR
to
\fINEW_LOGIN\fR\&. Nothing else is changed\&. In particular, the user\*(Aqs home directory or mail spool should probably be renamed manually to reflect the new login name\&.
.RE
.PP
\fB\-L\fR, \fB\-\-lock\fR
.RS 4
Lock a user\*(Aqs password\&. This puts a \*(Aq!\*(Aq in front of the encrypted password, effectively disabling the password\&. You can\*(Aqt use this option with
\fB\-p\fR
or
\fB\-U\fR\&.
.sp
Note: if you wish to lock the account (not only access with a password), you should also set the
\fIEXPIRE_DATE\fR
to
\fI1\fR\&.
.RE
.PP
\fB\-m\fR, \fB\-\-move\-home\fR
.RS 4
moves the content of the user\*(Aqs home directory to the new location\&. If the current home directory does not exist the new home directory will not be created\&.
.sp
This option is only valid in combination with the
\fB\-d\fR
(or
\fB\-\-home\fR) option\&.
.sp
\fBusermod\fR
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\&.
.RE
.PP
\fB\-o\fR, \fB\-\-non\-unique\fR
.RS 4
allows to change the user ID to a non\-unique value\&.
.sp
This option is only valid in combination with the
\fB\-u\fR
option\&. As a user identity serves as key to map between users on one hand and permissions, file ownerships and other aspects that determine the system\*(Aqs behavior on the other hand, more than one login name will access the account of the given UID\&.
.RE
.PP
\fB\-p\fR, \fB\-\-password\fR\ \&\fIPASSWORD\fR
.RS 4
defines a new password for the user\&. PASSWORD is expected to be encrypted, as returned by
\fBcrypt \fR(3)\&.
.sp
\fBNote:\fR
Avoid this option on the command line because the password (or encrypted password) will be visible by users listing the processes\&.
.sp
You should make sure the password respects the system\*(Aqs password policy\&.
.RE
.PP
\fB\-r\fR, \fB\-\-remove\fR
.RS 4
Remove the user from named supplementary group(s)\&. Use only with the
\fB\-G\fR
option\&.
.RE
.PP
\fB\-R\fR, \fB\-\-root\fR\ \&\fICHROOT_DIR\fR
.RS 4
Apply changes in the
\fICHROOT_DIR\fR
directory and use the configuration files from the
\fICHROOT_DIR\fR
directory\&. Only absolute paths are supported\&.
.RE
.PP
\fB\-P\fR, \fB\-\-prefix\fR\ \&\fIPREFIX_DIR\fR
.RS 4
Apply changes within the directory tree starting with
\fIPREFIX_DIR\fR
and use as well the configuration files located there\&. This option does not chroot and is intended for preparing a cross\-compilation target\&. Some limitations: NIS and LDAP users/groups are not verified\&. PAM authentication is using the host files\&. No SELINUX support\&.
.RE
.PP
\fB\-s\fR, \fB\-\-shell\fR\ \&\fISHELL\fR
.RS 4
changes the user\*(Aqs login shell\&. An empty string for SHELL blanks the field in
/etc/passwd
and logs the user into the system\*(Aqs default shell\&.
.RE
.PP
\fB\-u\fR, \fB\-\-uid\fR\ \&\fIUID\fR
.RS 4
The new value of the user\*(Aqs ID\&.
.sp
This value must be unique, unless the
\fB\-o\fR
option is used\&. The value must be non\-negative\&.
.sp
The user\*(Aqs mailbox, and any files which the user owns and which are located in the user\*(Aqs home directory will have the file user ID changed automatically\&.
.sp
The ownership of files outside of the user\*(Aqs home directory must be fixed manually\&.
.sp
The change of the user ownership of files inside of the user\*(Aqs home directory is also not done if the home dir owner uid is different from the current or new user id\&. This is a safety measure for special home directories such as
/\&.
.sp
No checks will be performed with regard to the
\fBUID_MIN\fR,
\fBUID_MAX\fR,
\fBSYS_UID_MIN\fR, or
\fBSYS_UID_MAX\fR
from
/etc/login\&.defs\&.
.RE
.PP
\fB\-U\fR, \fB\-\-unlock\fR
.RS 4
Unlock a user\*(Aqs password\&. This removes the \*(Aq!\*(Aq in front of the encrypted password\&. You can\*(Aqt use this option with
\fB\-p\fR
or
\fB\-L\fR\&.
.sp
Note: if you wish to unlock the account (not only access with a password), you should also set the
\fIEXPIRE_DATE\fR
(for example to
\fI99999\fR, or to the
\fBEXPIRE\fR
value from
/etc/default/useradd)\&.
.RE
.PP
\fB\-v\fR, \fB\-\-add\-subuids\fR\ \&\fIFIRST\fR\-\fILAST\fR
.RS 4
Add a range of subordinate uids to the user\*(Aqs account\&.
.sp
This option may be specified multiple times to add multiple ranges to a user\*(Aqs account\&.
.sp
No checks will be performed with regard to
\fBSUB_UID_MIN\fR,
\fBSUB_UID_MAX\fR, or
\fBSUB_UID_COUNT\fR
from /etc/login\&.defs\&.
.RE
.PP
\fB\-V\fR, \fB\-\-del\-subuids\fR\ \&\fIFIRST\fR\-\fILAST\fR
.RS 4
Remove a range of subordinate uids from the user\*(Aqs account\&.
.sp
This option may be specified multiple times to remove multiple ranges to a user\*(Aqs account\&. When both
\fB\-\-del\-subuids\fR
and
\fB\-\-add\-subuids\fR
are specified, the removal of all subordinate uid ranges happens before any subordinate uid range is added\&.
.sp
No checks will be performed with regard to
\fBSUB_UID_MIN\fR,
\fBSUB_UID_MAX\fR, or
\fBSUB_UID_COUNT\fR
from /etc/login\&.defs\&.
.RE
.PP
\fB\-w\fR, \fB\-\-add\-subgids\fR\ \&\fIFIRST\fR\-\fILAST\fR
.RS 4
Add a range of subordinate gids to the user\*(Aqs account\&.
.sp
This option may be specified multiple times to add multiple ranges to a user\*(Aqs account\&.
.sp
No checks will be performed with regard to
\fBSUB_GID_MIN\fR,
\fBSUB_GID_MAX\fR, or
\fBSUB_GID_COUNT\fR
from /etc/login\&.defs\&.
.RE
.PP
\fB\-W\fR, \fB\-\-del\-subgids\fR\ \&\fIFIRST\fR\-\fILAST\fR
.RS 4
Remove a range of subordinate gids from the user\*(Aqs account\&.
.sp
This option may be specified multiple times to remove multiple ranges to a user\*(Aqs account\&. When both
\fB\-\-del\-subgids\fR
and
\fB\-\-add\-subgids\fR
are specified, the removal of all subordinate gid ranges happens before any subordinate gid range is added\&.
.sp
No checks will be performed with regard to
\fBSUB_GID_MIN\fR,
\fBSUB_GID_MAX\fR, or
\fBSUB_GID_COUNT\fR
from /etc/login\&.defs\&.
.RE
.PP
\fB\-Z\fR, \fB\-\-selinux\-user\fR\ \&\fISEUSER\fR
.RS 4
defines the SELinux user to be mapped with
\fILOGIN\fR\&. An empty string ("") will remove the respective entry (if any)\&. Note that the shadow system doesn\*(Aqt store the selinux\-user, it uses semanage(8) for that\&.
.RE
.SH "CAVEATS"
.PP
You must make certain that the named user is not executing any processes when this command is being executed if the user\*(Aqs numerical user ID, the user\*(Aqs name, or the user\*(Aqs home directory is being changed\&.
\fBusermod\fR
checks this on Linux\&. On other operating systems it only uses utmp to check if the user is logged in\&.
.PP
You must change the owner of any
\fBcrontab\fR
files or
\fBat\fR
jobs manually\&.
.PP
You must make any changes involving NIS on the NIS server\&.
.SH "CONFIGURATION"
.PP
The following configuration variables in
/etc/login\&.defs
change the behavior of this tool:
.PP
\fBLASTLOG_UID_MAX\fR (number)
.RS 4
Highest user ID number for which the lastlog entries should be updated\&. As higher user IDs are usually tracked by remote user identity and authentication services there is no need to create a huge sparse lastlog file for them\&.
.sp
No
\fBLASTLOG_UID_MAX\fR
option present in the configuration means that there is no user ID limit for writing lastlog entries\&.
.RE
.PP
\fBMAIL_DIR\fR (string)
.RS 4
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\&. The parameter CREATE_MAIL_SPOOL in
/etc/default/useradd
determines whether the mail spool should be created\&.
.RE
.PP
\fBMAIL_FILE\fR (string)
.RS 4
Defines the location of the users mail spool files relatively to their home directory\&.
.RE
.PP
The
\fBMAIL_DIR\fR
and
\fBMAIL_FILE\fR
variables are used by
\fBuseradd\fR,
\fBusermod\fR, and
\fBuserdel\fR
to create, move, or delete the user\*(Aqs mail spool\&.
.PP
If
\fBMAIL_CHECK_ENAB\fR
is set to
\fIyes\fR, they are also used to define the
\fBMAIL\fR
environment variable\&.
.PP
\fBMAX_MEMBERS_PER_GROUP\fR (number)
.RS 4
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)\&.
.sp
The default value is 0, meaning that there are no limits in the number of members in a group\&.
.sp
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\&.
.sp
If you need to enforce such limit, you can use 25\&.
.sp
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\&.
.RE
.PP
\fBSUB_GID_MIN\fR (number), \fBSUB_GID_MAX\fR (number), \fBSUB_GID_COUNT\fR (number)
.RS 4
If
/etc/subuid
exists, the commands
\fBuseradd\fR
and
\fBnewusers\fR
(unless the user already have subordinate group IDs) allocate
\fBSUB_GID_COUNT\fR
unused group IDs from the range
\fBSUB_GID_MIN\fR
to
\fBSUB_GID_MAX\fR
for each new user\&.
.sp
The default values for
\fBSUB_GID_MIN\fR,
\fBSUB_GID_MAX\fR,
\fBSUB_GID_COUNT\fR
are respectively 100000, 600100000 and 65536\&.
.RE
.PP
\fBSUB_UID_MIN\fR (number), \fBSUB_UID_MAX\fR (number), \fBSUB_UID_COUNT\fR (number)
.RS 4
If
/etc/subuid
exists, the commands
\fBuseradd\fR
and
\fBnewusers\fR
(unless the user already have subordinate user IDs) allocate
\fBSUB_UID_COUNT\fR
unused user IDs from the range
\fBSUB_UID_MIN\fR
to
\fBSUB_UID_MAX\fR
for each new user\&.
.sp
The default values for
\fBSUB_UID_MIN\fR,
\fBSUB_UID_MAX\fR,
\fBSUB_UID_COUNT\fR
are respectively 100000, 600100000 and 65536\&.
.RE
.SH "FILES"
.PP
/etc/group
.RS 4
Group account information
.RE
.PP
/etc/gshadow
.RS 4
Secure group account informatio\&.
.RE
.PP
/etc/login\&.defs
.RS 4
Shadow password suite configuration
.RE
.PP
/etc/passwd
.RS 4
User account information
.RE
.PP
/etc/shadow
.RS 4
Secure user account information
.RE
.PP
/etc/subgid
.RS 4
Per user subordinate group IDs
.RE
.PP
/etc/subuid
.RS 4
Per user subordinate user IDs
.RE
.SH "SEE ALSO"
.PP
\fBchfn\fR(1),
\fBchsh\fR(1),
\fBpasswd\fR(1),
\fBcrypt\fR(3),
\fBgpasswd\fR(8),
\fBgroupadd\fR(8),
\fBgroupdel\fR(8),
\fBgroupmod\fR(8),
\fBlogin.defs\fR(5),
\fBsubgid\fR(5), \fBsubuid\fR(5),
\fBuseradd\fR(8),
\fBuserdel\fR(8)\&.