guix.texi

@end deftp

@defvr {Scheme Variable} %nscd-default-caches
List of @code{<nscd-cache>} objects used by default by
@code{nscd-configuration} (see above).

It enables persistent and aggressive caching of service and host name
lookups.  The latter provides better host name lookup performance,
resilience in the face of unreliable name servers, and also better
privacy---often the result of host name lookups is in local cache, so
external name servers do not even need to be queried.
@end defvr

@anchor{syslog-configuration-type}
@cindex syslog
@cindex logging
@deftp {Data Type} syslog-configuration
This data type represents the configuration of the syslog daemon.

@table @asis
@item @code{syslogd} (default: @code{#~(string-append #$inetutils "/libexec/syslogd")})
The syslog daemon to use.

@item @code{config-file} (default: @code{%default-syslog.conf})
The syslog configuration file to use.

@end table
@end deftp

@anchor{syslog-service}
@cindex syslog
@deffn {Scheme Procedure} syslog-service @var{config}
Return a service that runs a syslog daemon according to @var{config}.

@xref{syslogd invocation,,, inetutils, GNU Inetutils}, for more
information on the configuration file syntax.
@end deffn

@anchor{guix-configuration-type}
@deftp {Data Type} guix-configuration
This data type represents the configuration of the Guix build daemon.
@xref{Invoking guix-daemon}, for more information.

@table @asis
@item @code{guix} (default: @var{guix})
The Guix package to use.

@item @code{build-group} (default: @code{"guixbuild"})
Name of the group for build user accounts.

@item @code{build-accounts} (default: @code{10})
Number of build user accounts to create.

@item @code{authorize-key?} (default: @code{#t})
@cindex substitutes, authorization thereof
Whether to authorize the substitute keys listed in
@code{authorized-keys}---by default that of @code{hydra.gnu.org}
(@pxref{Substitutes}).

@vindex %default-authorized-guix-keys
@item @code{authorized-keys} (default: @var{%default-authorized-guix-keys})
The list of authorized key files for archive imports, as a list of
string-valued gexps (@pxref{Invoking guix archive}).  By default, it
contains that of @code{hydra.gnu.org} (@pxref{Substitutes}).

@item @code{use-substitutes?} (default: @code{#t})
Whether to use substitutes.

@item @code{substitute-urls} (default: @var{%default-substitute-urls})
The list of URLs where to look for substitutes by default.

@item @code{extra-options} (default: @code{'()})
List of extra command-line options for @command{guix-daemon}.

@item @code{log-file} (default: @code{"/var/log/guix-daemon.log"})
File where @command{guix-daemon}'s standard output and standard error
are written.

@item @code{lsof} (default: @var{lsof})
The lsof package to use.

@item @code{http-proxy} (default: @code{#f})
The HTTP proxy used for downloading fixed-output derivations and
substitutes.

@item @code{tmpdir} (default: @code{#f})
A directory path where the @command{guix-daemon} will perform builds.

@end table
@end deftp

@deffn {Scheme Procedure} guix-service @var{config}
Return a service that runs the Guix build daemon according to
@var{config}.
@end deffn

@deffn {Scheme Procedure} udev-service [#:udev udev]
Run @var{udev}, which populates the @file{/dev} directory dynamically.
@end deffn

@deffn {Scheme Procedure} urandom-seed-service @var{#f}
Save some entropy in @var{%random-seed-file} to seed @file{/dev/urandom}
when rebooting.
@end deffn

@defvr {Scheme Variable} %random-seed-file
This is the name of the file where some random bytes are saved by
@var{urandom-seed-service} to seed @file{/dev/urandom} when rebooting.
It defaults to @file{/var/lib/random-seed}.
@end defvr

@cindex keymap
@cindex keyboard
@deffn {Scheme Procedure} console-keymap-service @var{files} ...
@cindex keyboard layout
Return a service to load console keymaps from @var{files} using
@command{loadkeys} command.  Most likely, you want to load some default
keymap, which can be done like this:

@example
(console-keymap-service "dvorak")
@end example

Or, for example, for a Swedish keyboard, you may need to combine
the following keymaps:
@example
(console-keymap-service "se-lat6" "se-fi-lat6")
@end example

Also you can specify a full file name (or file names) of your keymap(s).
See @code{man loadkeys} for details.

@end deffn

@cindex mouse
@cindex gpm
@deffn {Scheme Procedure} gpm-service [#:gpm @var{gpm}] @
          [#:options]
Run @var{gpm}, the general-purpose mouse daemon, with the given
command-line @var{options}.  GPM allows users to use the mouse in the console,
notably to select, copy, and paste text.  The default value of @var{options}
uses the @code{ps2} protocol, which works for both USB and PS/2 mice.

This service is not part of @var{%base-services}.
@end deffn

@anchor{guix-publish-service-type}
@deffn {Scheme Variable} guix-publish-service-type
This is the service type for @command{guix publish} (@pxref{Invoking
guix publish}).  Its value must be a @code{guix-configuration}
object, as described below.

This assumes that @file{/etc/guix} already contains a signing key pair as
created by @command{guix archive --generate-key} (@pxref{Invoking guix
archive}).  If that is not the case, the service will fail to start.
@end deffn

@deftp {Data Type} guix-publish-configuration
Data type representing the configuration of the @code{guix publish}
service.

@table @asis
@item @code{guix} (default: @code{guix})
The Guix package to use.

@item @code{port} (default: @code{80})
The TCP port to listen for connections.

@item @code{host} (default: @code{"localhost"})
The host (and thus, network interface) to listen to.  Use
@code{"0.0.0.0"} to listen on all the network interfaces.

@item @code{compression-level} (default: @code{3})
The gzip compression level at which substitutes are compressed.  Use
@code{0} to disable compression altogether, and @code{9} to get the best
compression ratio at the expense of increased CPU usage.

@item @code{nar-path} (default: @code{"nar"})
The URL path at which ``nars'' can be fetched.  @xref{Invoking guix
publish, @code{--nar-path}}, for details.

@item @code{cache} (default: @code{#f})
When it is @code{#f}, disable caching and instead generate archives on
demand.  Otherwise, this should be the name of a directory---e.g.,
@code{"/var/cache/guix/publish"}---where @command{guix publish} caches
archives and meta-data ready to be sent.  @xref{Invoking guix publish,
@option{--cache}}, for more information on the tradeoffs involved.

@item @code{workers} (default: @code{#f})
When it is an integer, this is the number of worker threads used for
caching; when @code{#f}, the number of processors is used.
@xref{Invoking guix publish, @option{--workers}}, for more information.

@item @code{ttl} (default: @code{#f})
When it is an integer, this denotes the @dfn{time-to-live} of the
published archives.  @xref{Invoking guix publish, @option{--ttl}}, for
more information.
@end table
@end deftp

@anchor{rngd-service}
@deffn {Scheme Procedure} rngd-service [#:rng-tools @var{rng-tools}] @
            [#:device "/dev/hwrng"]
Return a service that runs the @command{rngd} program from @var{rng-tools}
to add @var{device} to the kernel's entropy pool.  The service will fail if
@var{device} does not exist.
@end deffn

@anchor{pam-limits-service}
@cindex session limits
@cindex ulimit
@cindex priority
@deffn {Scheme Procedure} pam-limits-service [#:limits @var{limits}]

Return a service that installs a configuration file for the
@uref{http://linux-pam.org/Linux-PAM-html/sag-pam_limits.html,
@code{pam_limits} module}.  The procedure optionally takes a list of
@code{pam-limits-entry} values, which can be used to specify
@code{ulimit} limits and nice priority limits to user sessions.

The following limits definition sets two hard and soft limits for all
login sessions of users in the @code{realtime} group:

@example
(pam-limits-service
 (list
  (pam-limits-entry "@@realtime" 'both 'rtprio 99)
  (pam-limits-entry "@@realtime" 'both 'memlock 'unlimited)))
@end example

The first entry increases the maximum realtime priority for
non-privileged processes; the second entry lifts any restriction of the
maximum address space that can be locked in memory.  These settings are
commonly used for real-time audio systems.
@end deffn

@node Scheduled Job Execution
@subsubsection Scheduled Job Execution

@cindex cron
@cindex mcron
@cindex scheduling jobs
The @code{(gnu services mcron)} module provides an interface to
GNU@tie{}mcron, a daemon to run jobs at scheduled times (@pxref{Top,,,
mcron, GNU@tie{}mcron}).  GNU@tie{}mcron is similar to the traditional
Unix @command{cron} daemon; the main difference is that it is
implemented in Guile Scheme, which provides a lot of flexibility when
specifying the scheduling of jobs and their actions.

The example below defines an operating system that runs the
@command{updatedb} (@pxref{Invoking updatedb,,, find, Finding Files})
and the @command{guix gc} commands (@pxref{Invoking guix gc}) daily, as
well as the @command{mkid} command on behalf of an unprivileged user
(@pxref{mkid invocation,,, idutils, ID Database Utilities}).  It uses
gexps to introduce job definitions that are passed to mcron
(@pxref{G-Expressions}).

@lisp
(use-modules (guix) (gnu) (gnu services mcron))
(use-package-modules base idutils)

(define updatedb-job
  ;; Run 'updatedb' at 3AM every day.  Here we write the
  ;; job's action as a Scheme procedure.
  #~(job '(next-hour '(3))
         (lambda ()
           (execl (string-append #$findutils "/bin/updatedb")
                  "updatedb"
                  "--prunepaths=/tmp /var/tmp /gnu/store"))))

(define garbage-collector-job
  ;; Collect garbage 5 minutes after midnight every day.
  ;; The job's action is a shell command.
  #~(job "5 0 * * *"            ;Vixie cron syntax
         "guix gc -F 1G"))

(define idutils-job
  ;; Update the index database as user "charlie" at 12:15PM
  ;; and 19:15PM.  This runs from the user's home directory.
  #~(job '(next-minute-from (next-hour '(12 19)) '(15))
         (string-append #$idutils "/bin/mkid src")
         #:user "charlie"))

(operating-system
  ;; @dots{}
  (services (cons (mcron-service (list garbage-collector-job
                                       updatedb-job
                                       idutils-job))
                  %base-services)))
@end lisp

@xref{Guile Syntax, mcron job specifications,, mcron, GNU@tie{}mcron},
for more information on mcron job specifications.  Below is the
reference of the mcron service.

@deffn {Scheme Procedure} mcron-service @var{jobs} [#:mcron @var{mcron2}]
Return an mcron service running @var{mcron} that schedules @var{jobs}, a
list of gexps denoting mcron job specifications.

This is a shorthand for:
@example
(service mcron-service-type
         (mcron-configuration (mcron mcron) (jobs jobs)))
@end example
@end deffn

@defvr {Scheme Variable} mcron-service-type
This is the type of the @code{mcron} service, whose value is an
@code{mcron-configuration} object.

This service type can be the target of a service extension that provides
it additional job specifications (@pxref{Service Composition}).  In
other words, it is possible to define services that provide additional
mcron jobs to run.
@end defvr

@deftp {Data Type} mcron-configuration
Data type representing the configuration of mcron.

@table @asis
@item @code{mcron} (default: @var{mcron2})
The mcron package to use.

@item @code{jobs}
This is a list of gexps (@pxref{G-Expressions}), where each gexp
corresponds to an mcron job specification (@pxref{Syntax, mcron job
specifications,, mcron, GNU@tie{}mcron}).
@end table
@end deftp


@node Log Rotation
@subsubsection Log Rotation

@cindex rottlog
@cindex log rotation
@cindex logging
Log files such as those found in @file{/var/log} tend to grow endlessly,
so it's a good idea to @dfn{rotate} them once in a while---i.e., archive
their contents in separate files, possibly compressed.  The @code{(gnu
services admin)} module provides an interface to GNU@tie{}Rot[t]log, a
log rotation tool (@pxref{Top,,, rottlog, GNU Rot[t]log Manual}).

The example below defines an operating system that provides log rotation
with the default settings.

@lisp
(use-modules (guix) (gnu))
(use-service-modules admin mcron)
(use-package-modules base idutils)

(operating-system
  ;; @dots{}
  (services (cons* (mcron-service)
                   (service rottlog-service-type)
                   %base-services)))
@end lisp

@defvr {Scheme Variable} rottlog-service-type
This is the type of the Rottlog service, whose value is a
@code{rottlog-configuration} object.

This service type can define mcron jobs (@pxref{Scheduled Job
Execution}) to run the rottlog service.
@end defvr

@deftp {Data Type} rottlog-configuration
Data type representing the configuration of rottlog.

@table @asis
@item @code{rottlog} (default: @code{rottlog})
The Rottlog package to use.

@item @code{rc-file} (default: @code{(file-append rottlog "/etc/rc")})
The Rottlog configuration file to use (@pxref{Mandatory RC Variables,,,
rottlog, GNU Rot[t]log Manual}).

@item @code{periodic-rotations} (default: @code{`(("weekly" %default-rotations))})
A list of Rottlog period-name/period-config tuples.

For example, taking an example from the Rottlog manual (@pxref{Period
Related File Examples,,, rottlog, GNU Rot[t]log Manual}), a valid tuple
might be:

@example
("daily" ,(plain-file "daily"
                      "\
     /var/log/apache/* @{
        storedir apache-archives
        rotate 6
        notifempty
        nocompress
     @}"))
@end example

@item @code{jobs}
This is a list of gexps where each gexp corresponds to an mcron job
specification (@pxref{Scheduled Job Execution}).
@end table
@end deftp

@defvr {Scheme Variable} %default-rotations
Specifies weekly rotation of @var{%rotated-files} and
@code{"/var/log/shepherd.log"}.
@end defvr

@defvr {Scheme Variable} %rotated-files
The list of syslog-controlled files to be rotated.  By default it is:
@code{'("/var/log/messages" "/var/log/secure")}.
@end defvr

@node Networking Services
@subsubsection Networking Services

The @code{(gnu services networking)} module provides services to configure
the network interface.

@cindex DHCP, networking service
@deffn {Scheme Procedure} dhcp-client-service [#:dhcp @var{isc-dhcp}]
Return a service that runs @var{dhcp}, a Dynamic Host Configuration
Protocol (DHCP) client, on all the non-loopback network interfaces.
@end deffn

@defvr {Scheme Variable} static-networking-service-type
This is the type for statically-configured network interfaces.
@c TODO Document <static-networking> data structures.
@end defvr

@deffn {Scheme Procedure} static-networking-service @var{interface} @var{ip} @
       [#:netmask #f] [#:gateway #f] [#:name-servers @code{'()}]
Return a service that starts @var{interface} with address @var{ip}.  If
@var{netmask} is true, use it as the network mask.  If @var{gateway} is true,
it must be a string specifying the default network gateway.

This procedure can be called several times, one for each network
interface of interest.  Behind the scenes what it does is extend
@code{static-networking-service-type} with additional network interfaces
to handle.
@end deffn

@cindex wicd
@cindex wireless
@cindex WiFi
@cindex network management
@deffn {Scheme Procedure} wicd-service [#:wicd @var{wicd}]
Return a service that runs @url{https://launchpad.net/wicd,Wicd}, a network
management daemon that aims to simplify wired and wireless networking.

This service adds the @var{wicd} package to the global profile, providing
several commands to interact with the daemon and configure networking:
@command{wicd-client}, a graphical user interface, and the @command{wicd-cli}
and @command{wicd-curses} user interfaces.
@end deffn

@cindex NetworkManager

@defvr {Scheme Variable} network-manager-service-type
This is the service type for the
@uref{https://wiki.gnome.org/Projects/NetworkManager, NetworkManager}
service. The value for this service type is a
@code{network-manager-configuration} record.
@end defvr

@deftp {Data Type} network-manager-configuration
Data type representing the configuration of NetworkManager.

@table @asis
@item @code{network-manager} (default: @code{network-manager})
The NetworkManager package to use.

@item @code{dns} (default: @code{"default"})
Processing mode for DNS, which affects how NetworkManager uses the
@code{resolv.conf} configuration file.

@table @samp
@item default
NetworkManager will update @code{resolv.conf} to reflect the nameservers
provided by currently active connections.

@item dnsmasq
NetworkManager will run @code{dnsmasq} as a local caching nameserver,
using a "split DNS" configuration if you are connected to a VPN, and
then update @code{resolv.conf} to point to the local nameserver.

@item none
NetworkManager will not modify @code{resolv.conf}.
@end table

@end table
@end deftp

@cindex Connman
@deffn {Scheme Variable} connman-service-type
This is the service type to run @url{https://01.org/connman,Connman},
a network connection manager.

Its value must be an
@code{connman-configuration} record as in this example:

@example
(service connman-service-type
         (connman-configuration
           (disable-vpn? #t)))
@end example

See below for details about @code{connman-configuration}.
@end deffn

@deftp {Data Type} connman-configuration
Data Type representing the configuration of connman.

@table @asis
@item @code{connman} (default: @var{connman})
The connman package to use.

@item @code{disable-vpn?} (default: @code{#f})
When true, enable connman's vpn plugin.
@end table
@end deftp

@cindex WPA Supplicant
@defvr {Scheme Variable} wpa-supplicant-service-type
This is the service type to run @url{https://w1.fi/wpa_supplicant/,WPA
supplicant}, an authentication daemon required to authenticate against
encrypted WiFi or ethernet networks.  It is configured to listen for
requests on D-Bus.

The value of this service is the @code{wpa-supplicant} package to use.
Thus, it can be instantiated like this:

@lisp
(use-modules (gnu services networking))

(service wpa-supplicant-service-type)
@end lisp
@end defvr

@cindex NTP
@cindex real time clock
@deffn {Scheme Procedure} ntp-service [#:ntp @var{ntp}] @
  [#:servers @var{%ntp-servers}] @
  [#:allow-large-adjustment? #f]
Return a service that runs the daemon from @var{ntp}, the
@uref{http://www.ntp.org, Network Time Protocol package}.  The daemon will
keep the system clock synchronized with that of @var{servers}.
@var{allow-large-adjustment?} determines whether @command{ntpd} is allowed to
make an initial adjustment of more than 1,000 seconds.
@end deffn

@defvr {Scheme Variable} %ntp-servers
List of host names used as the default NTP servers.
@end defvr

@cindex inetd
@deffn {Scheme variable} inetd-service-type
This service runs the @command{inetd} (@pxref{inetd invocation,,,
inetutils, GNU Inetutils}) daemon.  @command{inetd} listens for
connections on internet sockets, and lazily starts the specified server
program when a connection is made on one of these sockets.

The value of this service is an @code{inetd-configuration} object.  The
following example configures the @command{inetd} daemon to provide the
built-in @command{echo} service, as well as an smtp service which
forwards smtp traffic over ssh to a server @code{smtp-server} behind a
gateway @code{hostname}:

@example
(service
 inetd-service-type
 (inetd-configuration
  (entries (list
            (inetd-entry
             (name "echo")
             (socket-type 'stream)
             (protocol "tcp")
             (wait? #f)
             (user "root"))
            (inetd-entry
             (node "127.0.0.1")
             (name "smtp")
             (socket-type 'stream)
             (protocol "tcp")
             (wait? #f)
             (user "root")
             (program (file-append openssh "/bin/ssh"))
             (arguments
              '("ssh" "-qT" "-i" "/path/to/ssh_key"
                "-W" "smtp-server:25" "user@@hostname")))))
@end example

See below for more details about @code{inetd-configuration}.
@end deffn

@deftp {Data Type} inetd-configuration
Data type representing the configuration of @command{inetd}.

@table @asis
@item @code{program} (default: @code{(file-append inetutils "/libexec/inetd")})
The @command{inetd} executable to use.

@item @code{entries} (default: @code{'()})
A list of @command{inetd} service entries.  Each entry should be created
by the @code{inetd-entry} constructor.
@end table
@end deftp

@deftp {Data Type} inetd-entry
Data type representing an entry in the @command{inetd} configuration.
Each entry corresponds to a socket where @command{inetd} will listen for
requests.

@table @asis
@item @code{node} (default: @code{#f})
Optional string, a comma-separated list of local addresses
@command{inetd} should use when listening for this service.
@xref{Configuration file,,, inetutils, GNU Inetutils} for a complete
description of all options.
@item @code{name}
A string, the name must correspond to an entry in @code{/etc/services}.
@item @code{socket-type}
One of @code{'stream}, @code{'dgram}, @code{'raw}, @code{'rdm} or
@code{'seqpacket}.
@item @code{protocol}
A string, must correspond to an entry in @code{/etc/protocols}.
@item @code{wait?} (default: @code{#t})
Whether @command{inetd} should wait for the server to exit before
listening to new service requests.
@item @code{user}
A string containing the user (and, optionally, group) name of the user
as whom the server should run.  The group name can be specified in a
suffix, separated by a colon or period, i.e. @code{"user"},
@code{"user:group"} or @code{"user.group"}.
@item @code{program} (default: @code{"internal"})
The server program which will serve the requests, or @code{"internal"}
if @command{inetd} should use a built-in service.
@item @code{arguments} (default: @code{'()})
A list strings or file-like objects, which are the server program's
arguments, starting with the zeroth argument, i.e. the name of the
program itself.  For @command{inetd}'s internal services, this entry
must be @code{'()} or @code{'("internal")}.
@end table

@xref{Configuration file,,, inetutils, GNU Inetutils} for a more
detailed discussion of each configuration field.
@end deftp

@cindex Tor
@deffn {Scheme Procedure} tor-service [@var{config-file}] [#:tor @var{tor}]
Return a service to run the @uref{https://torproject.org, Tor} anonymous
networking daemon.

The daemon runs as the @code{tor} unprivileged user.  It is passed
@var{config-file}, a file-like object, with an additional @code{User tor} line
and lines for hidden services added via @code{tor-hidden-service}.  Run
@command{man tor} for information about the configuration file.
@end deffn

@cindex hidden service
@deffn {Scheme Procedure} tor-hidden-service @var{name} @var{mapping}
Define a new Tor @dfn{hidden service} called @var{name} and implementing
@var{mapping}.  @var{mapping} is a list of port/host tuples, such as:

@example
 '((22 "127.0.0.1:22")
   (80 "127.0.0.1:8080"))
@end example

In this example, port 22 of the hidden service is mapped to local port 22, and
port 80 is mapped to local port 8080.

This creates a @file{/var/lib/tor/hidden-services/@var{name}} directory, where
the @file{hostname} file contains the @code{.onion} host name for the hidden
service.

See @uref{https://www.torproject.org/docs/tor-hidden-service.html.en, the Tor
project's documentation} for more information.
@end deffn

@deffn {Scheme Procedure} bitlbee-service [#:bitlbee bitlbee] @
         [#:interface "127.0.0.1"] [#:port 6667] @
         [#:extra-settings ""]
Return a service that runs @url{http://bitlbee.org,BitlBee}, a daemon that
acts as a gateway between IRC and chat networks.

The daemon will listen to the interface corresponding to the IP address
specified in @var{interface}, on @var{port}.  @code{127.0.0.1} means that only
local clients can connect, whereas @code{0.0.0.0} means that connections can
come from any networking interface.

In addition, @var{extra-settings} specifies a string to append to the
configuration file.
@end deffn

Furthermore, @code{(gnu services ssh)} provides the following services.
@cindex SSH
@cindex SSH server

@deffn {Scheme Procedure} lsh-service [#:host-key "/etc/lsh/host-key"] @
       [#:daemonic? #t] [#:interfaces '()] [#:port-number 22] @
       [#:allow-empty-passwords? #f] [#:root-login? #f] @
       [#:syslog-output? #t] [#:x11-forwarding? #t] @
       [#:tcp/ip-forwarding? #t] [#:password-authentication? #t] @
       [#:public-key-authentication? #t] [#:initialize? #t]
Run the @command{lshd} program from @var{lsh} to listen on port @var{port-number}.
@var{host-key} must designate a file containing the host key, and readable
only by root.

When @var{daemonic?} is true, @command{lshd} will detach from the
controlling terminal and log its output to syslogd, unless one sets
@var{syslog-output?} to false.  Obviously, it also makes lsh-service
depend on existence of syslogd service.  When @var{pid-file?} is true,
@command{lshd} writes its PID to the file called @var{pid-file}.

When @var{initialize?} is true, automatically create the seed and host key
upon service activation if they do not exist yet.  This may take long and
require interaction.

When @var{initialize?} is false, it is up to the user to initialize the
randomness generator (@pxref{lsh-make-seed,,, lsh, LSH Manual}), and to create
a key pair with the private key stored in file @var{host-key} (@pxref{lshd
basics,,, lsh, LSH Manual}).

When @var{interfaces} is empty, lshd listens for connections on all the
network interfaces; otherwise, @var{interfaces} must be a list of host names
or addresses.

@var{allow-empty-passwords?} specifies whether to accept log-ins with empty
passwords, and @var{root-login?} specifies whether to accept log-ins as
root.

The other options should be self-descriptive.
@end deffn

@cindex SSH
@cindex SSH server
@deffn {Scheme Variable} openssh-service-type
This is the type for the @uref{http://www.openssh.org, OpenSSH} secure
shell daemon, @command{sshd}.  Its value must be an
@code{openssh-configuration} record as in this example:

@example
(service openssh-service-type
         (openssh-configuration
           (x11-forwarding? #t)
           (permit-root-login 'without-password)))
@end example

See below for details about @code{openssh-configuration}.
@end deffn

@deftp {Data Type} openssh-configuration
This is the configuration record for OpenSSH's @command{sshd}.

@table @asis
@item @code{pid-file} (default: @code{"/var/run/sshd.pid"})
Name of the file where @command{sshd} writes its PID.

@item @code{port-number} (default: @code{22})
TCP port on which @command{sshd} listens for incoming connections.

@item @code{permit-root-login} (default: @code{#f})
This field determines whether and when to allow logins as root.  If
@code{#f}, root logins are disallowed; if @code{#t}, they are allowed.
If it's the symbol @code{'without-password}, then root logins are
permitted but not with password-based authentication.

@item @code{allow-empty-passwords?} (default: @code{#f})
When true, users with empty passwords may log in.  When false, they may
not.

@item @code{password-authentication?} (default: @code{#t})
When true, users may log in with their password.  When false, they have
other authentication methods.

@item @code{public-key-authentication?} (default: @code{#t})
When true, users may log in using public key authentication.  When
false, users have to use other authentication method.

Authorized public keys are stored in @file{~/.ssh/authorized_keys}.
This is used only by protocol version 2.

@item @code{x11-forwarding?} (default: @code{#f})
When true, forwarding of X11 graphical client connections is
enabled---in other words, @command{ssh} options @option{-X} and
@option{-Y} will work.

@item @code{challenge-response-authentication?} (default: @code{#f})
Specifies whether challenge response authentication is allowed (e.g. via
PAM).

@item @code{use-pam?} (default: @code{#t})
Enables the Pluggable Authentication Module interface.  If set to
@code{#t}, this will enable PAM authentication using
@code{challenge-response-authentication?} and
@code{password-authentication?}, in addition to PAM account and session
module processing for all authentication types.

Because PAM challenge response authentication usually serves an
equivalent role to password authentication, you should disable either
@code{challenge-response-authentication?} or
@code{password-authentication?}.

@item @code{print-last-log?} (default: @code{#t})
Specifies whether @command{sshd} should print the date and time of the
last user login when a user logs in interactively.

@item @code{subsystems} (default: @code{'(("sftp" "internal-sftp"))})
Configures external subsystems (e.g. file transfer daemon).

This is a list of two-element lists, each of which containing the
subsystem name and a command (with optional arguments) to execute upon
subsystem request.

The command @command{internal-sftp} implements an in-process SFTP
server.  Alternately, one can specify the @command{sftp-server} command:
@example
(service openssh-service-type
         (openssh-configuration
          (subsystems
           '(("sftp" ,(file-append openssh "/libexec/sftp-server"))))))
@end example
@end table
@end deftp

@deffn {Scheme Procedure} dropbear-service [@var{config}]
Run the @uref{https://matt.ucc.asn.au/dropbear/dropbear.html,Dropbear SSH
daemon} with the given @var{config}, a @code{<dropbear-configuration>}
object.

For example, to specify a Dropbear service listening on port 1234, add
this call to the operating system's @code{services} field:

@example
(dropbear-service (dropbear-configuration
                    (port-number 1234)))
@end example
@end deffn

@deftp {Data Type} dropbear-configuration
This data type represents the configuration of a Dropbear SSH daemon.

@table @asis
@item @code{dropbear} (default: @var{dropbear})
The Dropbear package to use.

@item @code{port-number} (default: 22)
The TCP port where the daemon waits for incoming connections.

@item @code{syslog-output?} (default: @code{#t})
Whether to enable syslog output.

@item @code{pid-file} (default: @code{"/var/run/dropbear.pid"})
File name of the daemon's PID file.

@item @code{root-login?} (default: @code{#f})
Whether to allow @code{root} logins.

@item @code{allow-empty-passwords?} (default: @code{#f})
Whether to allow empty passwords.

@item @code{password-authentication?} (default: @code{#t})
Whether to enable password-based authentication.
@end table
@end deftp

@defvr {Scheme Variable} %facebook-host-aliases
This variable contains a string for use in @file{/etc/hosts}
(@pxref{Host Names,,, libc, The GNU C Library Reference Manual}).  Each
line contains a entry that maps a known server name of the Facebook
on-line service---e.g., @code{www.facebook.com}---to the local
host---@code{127.0.0.1} or its IPv6 equivalent, @code{::1}.

This variable is typically used in the @code{hosts-file} field of an
@code{operating-system} declaration (@pxref{operating-system Reference,
@file{/etc/hosts}}):

@example
(use-modules (gnu) (guix))

(operating-system
  (host-name "mymachine")
  ;; ...
  (hosts-file
    ;; Create a /etc/hosts file with aliases for "localhost"
    ;; and "mymachine", as well as for Facebook servers.
    (plain-file "hosts"
                (string-append (local-host-aliases host-name)
                               %facebook-host-aliases))))
@end example

This mechanism can prevent programs running locally, such as Web
browsers, from accessing Facebook.
@end defvr

The @code{(gnu services avahi)} provides the following definition.

@deffn {Scheme Procedure} avahi-service [#:avahi @var{avahi}] @
          [#:host-name #f] [#:publish? #t] [#:ipv4? #t] @
          [#:ipv6? #t] [#:wide-area? #f] @
          [#:domains-to-browse '()] [#:debug? #f]
Return a service that runs @command{avahi-daemon}, a system-wide
mDNS/DNS-SD responder that allows for service discovery and
"zero-configuration" host name lookups (see @uref{http://avahi.org/}), and
extends the name service cache daemon (nscd) so that it can resolve
@code{.local} host names using
@uref{http://0pointer.de/lennart/projects/nss-mdns/, nss-mdns}.  Additionally,
add the @var{avahi} package to the system profile so that commands such as
@command{avahi-browse} are directly usable.

If @var{host-name} is different from @code{#f}, use that as the host name to
publish for this machine; otherwise, use the machine's actual host name.

When @var{publish?} is true, publishing of host names and services is allowed;
in particular, avahi-daemon will publish the machine's host name and IP
address via mDNS on the local network.

When @var{wide-area?} is true, DNS-SD over unicast DNS is enabled.

Boolean values @var{ipv4?} and @var{ipv6?} determine whether to use IPv4/IPv6
sockets.
@end deffn

@deffn {Scheme Variable} openvswitch-service-type
This is the type of the @uref{http://www.openvswitch.org, Open vSwitch}
service, whose value should be an @code{openvswitch-configuration}
object.
@end deffn

@deftp {Data Type} openvswitch-configuration
Data type representing the configuration of Open vSwitch, a multilayer
virtual switch which is designed to enable massive network automation
through programmatic extension.

@table @asis
@item @code{package} (default: @var{openvswitch})
Package object of the Open vSwitch.

@end table
@end deftp

@node X Window
@subsubsection X Window

@cindex X11
@cindex X Window System
Support for the X Window graphical display system---specifically
Xorg---is provided by the @code{(gnu services xorg)} module.  Note that
there is no @code{xorg-service} procedure.  Instead, the X server is
started by the @dfn{login manager}, currently SLiM.

@deftp {Data Type} sddm-configuration
This is the data type representing the sddm service configuration.

@table @asis
@item @code{display-server} (default: "x11")
Select display server to use for the greeter. Valid values are "x11"
or "wayland".

@item @code{numlock} (default: "on")
Valid values are "on", "off" or "none".

@item @code{halt-command} (default @code{#~(string-apppend #$shepherd "/sbin/halt")})
Command to run when halting.

@item @code{reboot-command} (default @code{#~(string-append #$shepherd "/sbin/reboot")})
Command to run when rebooting.

@item @code{theme} (default "maldives")
Theme to use. Default themes provided by SDDM are "elarun" or "maldives".

@item @code{themes-directory} (default "/run/current-system/profile/share/sddm/themes")
Directory to look for themes.

@item @code{faces-directory} (default "/run/current-system/profile/share/sddm/faces")
Directory to look for faces.

@item @code{default-path} (default "/run/current-system/profile/bin")
Default PATH to use.

@item @code{minimum-uid} (default 1000)
Minimum UID to display in SDDM.

@item @code{maximum-uid} (default 2000)
Maximum UID to display in SDDM

@item @code{remember-last-user?} (default #t)
Remember last user.

@item @code{remember-last-session?} (default #t)
Remember last session.

@item @code{hide-users} (default "")
Usernames to hide from SDDM greeter.

@item @code{hide-shells} (default @code{#~(string-append #$shadow "/sbin/nologin")})
Users with shells listed will be hidden from the SDDM greeter.

@item @code{session-command} (default @code{#~(string-append #$sddm "/share/sddm/scripts/wayland-session")})
Script to run before starting a wayland session.