Ubuntu Manpage: realmd.conf - Tweak behavior of realmd

NAME

       realmd.conf - Tweak behavior of realmd

CONFIGURATION FILE

realmd can be tweaked by network administrators to act in specific ways. This is done by
placing settings in a /etc/realmd.conf. This file does not exist by default. The syntax of
this file is the same as an INI file or Desktop Entry file. If the file is changed and
realmd is running realmd must be restarted to read the new values.

In general, settings in this file only apply at the point of joining a domain or realm.
Once the realm has been setup the settings have no effect. You may choose to configure
SSSD[1] or Winbind[2] directly.

Only specify the settings you wish to override in the /etc/realmd.conf file. Settings not
specified will be loaded from their packaged defaults which can be found in
/usr/lib/realmd/realmd-defaults.conf and /usr/lib/realmd/realmd-distro.conf. Only override
the settings below. You may find other settings if you look through the realmd source
code. However these are not guaranteed to remain stable.

There are various sections in the config file. Some sections are global topic sections,
and are listed below. Other sections are specific to a given realm. These realm specific
sections should always contain the domain name in lower case as their section header.

Examples of each setting is found below, including the header of the section it should be
placed in. However in the resulting file only include each section once, and combine the
various section setting together as lines underneath the section. For example

[users]
default-home = /home/%U
default-shell = /bin/bash

ACTIVE-DIRECTORY

These options should go in an [active-directory] section of the /etc/realmd.conf file.
Only specify the settings you wish to override.

default-client
Specify the default-client setting in order to control which client software is the
preferred default for use with Active Directory.

[active-directory]
default-client = sssd
# default-client = winbind

The default setting for this is sssd which uses SSSD[1] as the Active Directory
client. You can also specify winbind to use Samba Winbind[2].

Some callers of realmd such as the realm command line tool allow specifying which
client software should be used. Others, such as GNOME Control Center, simplify choose
the default.

You can verify the preferred default client softawre by running the following command.
The realm with the preferred client software will be listed first.

$ realm discover domain.example.com
domain.example.com
configured: no
server-software: active-directory
client-software: sssd
type: kerberos
realm-name: AD.THEWALTER.LAN
domain-name: ad.thewalter.lan
domain.example.com
configured: no
server-software: active-directory
client-software: winbind
type: kerberos
realm-name: AD.THEWALTER.LAN
domain-name: ad.thewalter.lan

use-ldaps
Use the ldaps port when connecting to AD where possible. In general this option is not
needed because realmd itself only read public information from the Active Directory
domain controller which is available anonymously. The supported membership software
products will use encrypted connections protected with GSS-SPNEGO/GSSAPI which offers
a comparable level of security than ldaps. This option is only needed if the standard
LDAP port (389/tcp) is blocked by a firewall and only the LDAPS port (636/tcp) is
available.

If this option is set to yes realmd will use the ldaps port when reading the rootDSE
and call the adcli membership software with the option --use-ldaps. The Samba base
membership currently offers only deprecated ways to enable ldaps. Support will be
added in realmd when a new way is available.

os-name
(see below)

os-version
Specify the os-name and/or os-version settings to control the values that are placed
in the computer account operatingSystem and operatingSystemVersion attributes.

This is an Active Directory specific option.

It is also possible to use the --os-name or --os-version argument of the realm command
to override the default values.

[active-directory]
os-name = Gentoo Linux
os-version = 9.9.9.9.9

SERVICE

       These options should go in an [service] section of the /etc/realmd.conf file. Only specify
       the settings you wish to override.

       automatic-install
           Set this to no to disable automatic installation of packages via package-kit.

               [service]
               automatic-install = no
               # automatic-install = yes

       legacy-samba-config
           Set this to yes to create a Samba configuration file with id-mapping options used by
           Samba-3.5 and earlier version.

               [service]
               legacy-samba-config = no
               # legacy-samba-config = yes

USERS

These options should go in an [users] section of the /etc/realmd.conf file. Only specify
the settings you wish to override.

default-home
Specify the default-home setting in order to control how to set the home directory for
accounts that have no home directory explicitly set.

[users]
default-home = /home/%U@%D
# default-home = /nfs/home/%D-%U
# default-home = /home/%D/%U

The default setting for this is /home/%U@%D. The %D format is replaced by the domain
name. The %U format is replaced by the user name.

You can verify the home directory for a user by running the following command.

$ getent passwd 'DOMAIN/User'
DOMAIN\user:*:13445:13446:Name:/home/DOMAIN/user:/bin/bash
Note that in the case of IPA domains, most users already have a home directory
configured in the domain. Therefore this configuration setting may rarely show
through.

default-shell
Specify the default-shell setting in order to control how to set the Unix shell for
accounts that have no shell explicitly set.

[users]
default-shell = /bin/bash
# default-shell = /bin/sh

The default setting for this is /bin/bash shell. The shell should be a valid shell if
you expect the domain users be able to log in. For example it should exist in the
/etc/shells file.

You can verify the shell for a user by running the following command.

$ getent passwd 'DOMAIN/User'
DOMAIN\user:*:13445:13446:Name:/home/DOMAIN/user:/bin/bash
Note that in the case of IPA domains, most users already have a shell configured in
the domain. Therefore this configuration setting may rarely show through.

PATHS

These options should go in an [paths] section of the /etc/realmd.conf file. Only specify
the settings you wish to override.

krb5.conf
Path to the Kerberos configuration file, typically /etc/krb5.conf. It can also be the
path of a file included by /etc/krb5.conf, e.g. /etc/krb5.conf.d/realmd_settings, if
the file does not exist if will be created.

[paths]
krb5.conf = /etc/krb5.conf.d/realmd_settings

When joining an Active Directory domain realmd will set the default_realm and
udp_preference_limit options in the Kerberos configuration:

default_realm = DOMAIN.EXAMPLE.COM
udp_preference_limit = 0

The default_realm option is e.g. needed when trying to resolve enterprise principals
and makes it more convenient to request Kerberos tickets for users of the default
realm. Instead of specifying the whole principal just kinit username can be used.

With udp_preference_limit = 0 always TCP will be used to send Kerberos request to
domain controller. This is useful in Active Directory environments because Kerberos
will typically switch to TCP after initially starting with UDP because AD Kerberos
tickets are often larger than UDP can handle. Using TCP by default will avoid those
extra UDP round trips. Additionally it helps to avoid issues with password changes
when the DC does not reply soon enough and the client will send a second UDP request.
The DC might reply with a reply error to the second request although the original
password change request was successful and the client will no know if the request was
successful or not. When using TCP this cannot happen because the client will never
send a second request but waits on the connection until the server replies.

Please note that realmd will not remove those options while leaving the domain since
they are useful in general. When joining a new domain realmd will of course overwrite
default_realm.

REALM SPECIFIC SETTINGS

These options should go in an section with the same name as the realm in the
/etc/realmd.conf file. For example for the domain.example.com domain the section would be
called [domain.example.com]. To figure out the canonical name for a realm use the realm
command:

$ realm discover --name-only DOMAIN.example.com
domain.example.com
...

Only specify the settings you wish to override.

computer-ou
Specify this option to create directory computer accounts in a location other than the
default. This currently only works with Active Directory domains.

[domain.example.com]
computer-ou = OU=Linux Computers,DC=domain,DC=example,DC=com
# computer-ou = OU=Linux Computers,

Specify the OU as an LDAP DN. It can be relative to the Root DSE, or a complete LDAP
DN. Obviously the OU must exist in the directory.

It is also possible to use the --computer-ou argument of the realm command to create a
computer account at a specific OU.

computer-name
This option only applied to Active Directory realms. Specify this option to override
the default name used when creating the computer account. The system's FQDN will still
be saved in the dNSHostName attribute.

[domain.example.com]
computer-name = SERVER01
Specify the name as a string of 15 or fewer characters that is a valid NetBIOS
computer name.

It is also possible to use the --computer-name argument of the realm command to
override the default computer account name.

user-principal
Set the user-principal to yes to create userPrincipalName attribute for the computer
accounts in the realm. The exact value depends on the defaults of the used membership
software. To have full control over the value please use the --user-principal option
of the realm command, see realm(8) for details.

[domain.example.com]
user-principal = yes

automatic-join
This option only applies to Active Directory realms. This option is off by default. In
Active Directory domains, a computer account can be preset with a known computer
account password. This can be used for automatic joins without authentication.

When automatic joins are used there is no mutual authentication between the machine
and the domain during the join process.

[domain.example.com]
automatic-join = yes

automatic-id-mapping
This option is on by default for Active Directory realms. Turn it off to use UID and
GID information stored in the directory (as-per RFC2307) rather than automatically
generating UID and GID numbers.

This option only makes sense for Active Directory realms.

[domain.example.com]
automatic-id-mapping = no
# automatic-id-mapping = yes

manage-system
This option is on by default. Normally joining a realm affects many aspects of the
configuration and management of the system. Turning this off limits the interaction
with the realm or domain to authentication and identity.

[domain.example.com]
manage-system = no
# manage-system = yes

When this option is turned on realmd defaults to using domain policy to control who
can log into this machine. Further adjustments to login policy can be made with the
realm permit command.

fully-qualified-names
This option is on by default. If turned off then realm user and group names are not
qualified their name. This may cause them to conflict with local user and group names.

[domain.example.com]
fully-qualified-names = no
# fully-qualified-names = yes

AUTHOR

       Stef Walter <stef@thewalter.net>
           Maintainer

NOTES

        1. SSSD
           https://fedorahosted.org/sssd/

        2. Winbind
           http://www.samba.org/samba/docs/man/Samba-HOWTO-Collection/winbind.html