useradd.1m (2010 09)

useradd(1M) useradd(1M)

Add the user otto to the system with a UID of

222 and a primary group of staff.

useradd -u 222 -g staff otto

List the defaults for the primary group, base directory, inactivity timeout, and skeleton directory.

useradd -D

Change the default primary group to staff.

useradd -D -g staff

WARNINGS

A directory can be shared between the users belonging to the same group. If the home directory is in the

unshared mode and a new user is allocated to that directory then it will be put into the shared mode by

setting the permissions of that directory to 775

(includes the write permissions to the group as well).

Also, the directory which will be shared should have read and execute permissions for the group. Other-

wise,

useradd will report an error.

Because many users may try to write the

/etc/passwd ﬁle simultaneously, a password locking

mechanism was devised. If this password locking fails after subsequent retrying,

useradd terminates.

A group entry in the

/etc/group ﬁle can have maximum of

LINE_MAX bytes. See limits (5) for the

value of

LINE_MAX. If a user is added to a group that has reached LINE_MAX

limit, another entry of the

same group is created to which the new user is added. A warning message is also issued.

FILES

/etc/shadow Shadow Password ﬁle

/etc/passwd System Password ﬁle

/etc/skel Skeleton directory

/etc/group System group ﬁle

/etc/ptmp Lock ﬁle used when updating password ﬁle