kumquat-buildroot/docs/manual/makeusers-syntax.adoc
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Signed-off-by: Francois Perrad <francois.perrad@gadz.org>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
2023-09-30 10:25:22 +02:00

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// -*- mode:doc -*- ;
// vim: set syntax=asciidoc:
[[makeuser-syntax]]
== Makeusers syntax documentation
The syntax to create users is inspired by the makedev syntax, above, but
is specific to Buildroot.
The syntax for adding a user is a space-separated list of fields, one
user per line; the fields are:
|=================================================================
|username |uid |group |gid |password |home |shell |groups |comment
|=================================================================
Where:
- +username+ is the desired user name (aka login name) for the user.
It can not be +root+, and must be unique. If set to +-+, then just a
group will be created.
- +uid+ is the desired UID for the user. It must be unique, and not
+0+. If set to +-1+ or +-2+, then a unique UID will be computed by
Buildroot, with +-1+ denoting a system UID from [100...999] and +-2+
denoting a user UID from [1000...1999].
- +group+ is the desired name for the user's main group. It can not
be +root+. If the group does not exist, it will be created.
- +gid+ is the desired GID for the user's main group. It must be unique,
and not +0+. If set to +-1+ or +-2+, and the group does not already
exist, then a unique GID will be computed by Buildroot, with +-1+
denoting a system GID from [100...999] and +-2+ denoting a user GID
from [1000...1999].
- +password+ is the crypt(3)-encoded password. If prefixed with +!+,
then login is disabled. If prefixed with +=+, then it is interpreted
as clear-text, and will be crypt-encoded (using MD5). If prefixed with
+!=+, then the password will be crypt-encoded (using MD5) and login
will be disabled. If set to +*+, then login is not allowed. If set to
+-+, then no password value will be set.
- +home+ is the desired home directory for the user. If set to '-', no
home directory will be created, and the user's home will be +/+.
Explicitly setting +home+ to +/+ is not allowed.
- +shell+ is the desired shell for the user. If set to +-+, then
+/bin/false+ is set as the user's shell.
- +groups+ is the comma-separated list of additional groups the user
should be part of. If set to +-+, then the user will be a member of
no additional group. Missing groups will be created with an arbitrary
+gid+.
- +comment+ (aka https://en.wikipedia.org/wiki/Gecos_field[GECOS]
field) is an almost-free-form text.
There are a few restrictions on the content of each field:
* except for +comment+, all fields are mandatory.
* except for +comment+, fields may not contain spaces.
* no field may contain a colon (+:+).
If +home+ is not +-+, then the home directory, and all files below,
will belong to the user and its main group.
Examples:
----
foo -1 bar -1 !=blabla /home/foo /bin/sh alpha,bravo Foo user
----
This will create this user:
- +username+ (aka login name) is: +foo+
- +uid+ is computed by Buildroot
- main +group+ is: +bar+
- main group +gid+ is computed by Buildroot
- clear-text +password+ is: +blabla+, will be crypt(3)-encoded, and login is disabled.
- +home+ is: +/home/foo+
- +shell+ is: +/bin/sh+
- +foo+ is also a member of +groups+: +alpha+ and +bravo+
- +comment+ is: +Foo user+
----
test 8000 wheel -1 = - /bin/sh - Test user
----
This will create this user:
- +username+ (aka login name) is: +test+
- +uid+ is : +8000+
- main +group+ is: +wheel+
- main group +gid+ is computed by Buildroot, and will use the value defined in the rootfs skeleton
- +password+ is empty (aka no password).
- +home+ is +/+ but will not belong to +test+
- +shell+ is: +/bin/sh+
- +test+ is not a member of any additional +groups+
- +comment+ is: +Test user+
=== Caveat with automatic UIDs and GIDs
When updating buildroot or when packages are added or removed to/from
the configuration, it is possible that the automatic UIDs and GIDs are
changed. This can be a problem if persistent files were created with
that user or group: after upgrade, they will suddenly have a different
owner.
Therefore, it is advisable to perpetuate the automatic IDs. This can be
done by adding a users table with the generated IDs. It is only needed
to do this for UIDs that actually create persistent files, e.g. database.