usermod(8)

1USERMOD(8)                System Management Commands                USERMOD(8)
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NAME

6       usermod - modify a user account
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SYNOPSIS

9       usermod [options] LOGIN
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DESCRIPTION

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

16       The options which apply to the usermod command are:
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18       -a, --append
19           Add the user to the supplementary group(s). Use only with the -G
20           option.
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22       -c, --comment COMMENT
23           The new value of the user´s password file comment field. It is
24           normally modified using the chfn(1) utility.
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26       -d, --home HOME_DIR
27           The user´s new login directory.
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29           If the -m option is given, the contents of the current home
30           directory will be moved to the new home directory, which is created
31           if it does not already exist.
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33       -e, --expiredate EXPIRE_DATE
34           The date on which the user account will be disabled. The date is
35           specified in the format YYYY-MM-DD.
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37       -f, --inactive INACTIVE
38           The number of days after a password expires until the account is
39           permanently disabled.
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41           A value of 0 disables the account as soon as the password has
42           expired, and a value of -1 disables the feature.
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44       -g, --gid GROUP
45           The group name or number of the user´s new initial login group. The
46           group must exist.
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48       -G, --groups GROUP1[,GROUP2,...[,GROUPN]]]
49           A list of supplementary groups which the user is also a member of.
50           Each group is separated from the next by a comma, with no
51           intervening whitespace. The groups are subject to the same
52           restrictions as the group given with the -g option.
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54           If the user is currently a member of a group which is not listed,
55           the user will be removed from the group. This behaviour can be
56           changed via the -a option, which appends the user to the current
57           supplementary group list.
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59       -l, --login NEW_LOGIN
60           The name of the user will be changed from LOGIN to NEW_LOGIN.
61           Nothing else is changed. In particular, the user´s home directory
62           name should probably be changed manually to reflect the new login
63           name.
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65       -L, --lock
66           Lock a user´s password. This puts a ´!´ in front of the encrypted
67           password, effectively disabling the password. You can´t use this
68           option with -p or -U.
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70           Note: if you wish to lock the account (not only access with a
71           password), you should also set the EXPIRE_DATE to 1.
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73       -m, --move-home
74           Move the content of the user´s home directory to the new location.
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76           This option is only valid in combination with the -d (or --home)
77           option.
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79       -o, --non-unique
80           When used with the -u option, this option allows to change the user
81           ID to a non-unique value.
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83       -p, --password PASSWORD
84           The encrypted password, as returned by crypt(3).
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86
87           Note: This option is not recommended because the password (or
88           encrypted password) will be visible by users listing the processes.
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90           You should make sure the password respects the system´s password
91           policy.
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93       -s, --shell SHELL
94           The name of the user´s new login shell. Setting this field to blank
95           causes the system to select the default login shell.
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97       -u, --uid UID
98           The new numerical value of the user´s ID.
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100           This value must be unique, unless the -o option is used. The value
101           must be non-negative. Values between 0 and 999 are typically
102           reserved for system accounts.
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104           The user´s mailbox, and any files which the user owns and which are
105           located in the user´s home directory will have the file user ID
106           changed automatically.
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108           The ownership of files outside of the user´s home directory must be
109           fixed manually.
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111       -U, --unlock
112           Unlock a user´s password. This removes the ´!´ in front of the
113           encrypted password. You can´t use this option with -p or -L.
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115           Note: if you wish to unlock the account (not only access with a
116           password), you should also set the EXPIRE_DATE (for example to
117           99999, or to the EXPIRE value from /etc/default/useradd).
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119       -Z, --selinux-user SEUSER
120           The SELinux user for the user´s login. The default is to leave this
121           field the blank, which causes the system to select the default
122           SELinux user.
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CAVEATS

125       You must make certain that the named user is not executing any
126       processes when this command is being executed if the user´s numerical
127       user ID, the user´s name, or the user´s home directory is being
128       changed.  usermod checks this on Linux, but only check if the user is
129       logged in according to utmp on other architectures.
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131       You must change the owner of any crontab files or at jobs manually.
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133       You must make any changes involving NIS on the NIS server.
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CONFIGURATION

136       The following configuration variables in /etc/login.defs change the
137       behavior of this tool:
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139       MAIL_DIR (string)
140           The mail spool directory. This is needed to manipulate the mailbox
141           when its corresponding user account is modified or deleted. If not
142           specified, a compile-time default is used.
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144       MAIL_FILE (string)
145           Defines the location of the users mail spool files relatively to
146           their home directory.
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148       The MAIL_DIR and MAIL_FILE variables are used by useradd, usermod, and
149       userdel to create, move, or delete the user´s mail spool.
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151       If MAIL_CHECK_ENAB is set to yes, they are also used to define the MAIL
152       environment variable.
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154       MAX_MEMBERS_PER_GROUP (number)
155           Maximum members per group entry. When the maximum is reached, a new
156           group entry (line) is started in /etc/group (with the same name,
157           same password, and same GID).
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159           The default value is 0, meaning that there are no limits in the
160           number of members in a group.
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162           This feature (split group) permits to limit the length of lines in
163           the group file. This is useful to make sure that lines for NIS
164           groups are not larger than 1024 characters.
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166           If you need to enforce such limit, you can use 25.
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168           Note: split groups may not be supported by all tools (even in the
169           Shadow toolsuite). You should not use this variable unless you
170           really need it.
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FILES

173       /etc/group
174           Group account information.
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176       /etc/gshadow
177           Secure group account information.
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179       /etc/passwd
180           User account information.
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182       /etc/shadow
183           Secure user account information.
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