kumquat-buildroot/docs/manual/makeusers-syntax.txt
Norbert Lange 41ea61d59c support/scripts/mkusers: allow option for system uid/gid
Some software decides based on uid/gid whether a user is a system or
normal (human) user, with different behaviour for those flavors (example
journald [2]).

So adding logic to create system-users is necessary, we take the now
common ranges from [1].

This extends the mkusers script to allow -2 for uid/gid, this argument
will take an identifier from the user range. All identifiers used up to
now should have been from the system range, so -1 is now interpreted as
a system user/group.

Note that after this commit, all the UIDs and GIDs that are created
automatically (with -1) will change. That means if there is peristent
data on an existing system that was created by such an automatic user,
it will suddenly belong to a different user. However, this could already
happen before: if a USERS line is added to a package, then other UIDs
may change as well.

Add system/user ranges as variables, and the argument for user/system
uid variable as well. Thus some magic constants could be removed, some
further occurences of -1 were replaced with equivalent logic. For
consistency, the existing MIN/MAX_UID/GID variables are renamed to
FIRST/LAST_USER_UID/GID.

Update the documentation with the new automatic ranges.

[1] - https://systemd.io/UIDS-GIDS/
[2] - https://www.freedesktop.org/software/systemd/man/journald.conf.html

Signed-off-by: Norbert Lange <nolange79@gmail.com>
[Arnout: use -1 for system users; refactor the changes a bit]
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
2022-02-05 23:09:31 +01:00

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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+