nixpkgs/nixos/modules/services/printing/cupsd.nix
Michael Weiss ea23f8bb07 cups service: Automatically detect Gutenprint in drivers
Additional CUPS drivers can be added via "services.printing.drivers" but
Gutenprint was an exception. It was possible to add a Gutenprint
derivation to that list and it would work at first but unlike the other
drivers Gutenprint requires a script to be run after each update or any
attempt to print something would simply fail and an error would show up
in the jobs queue (http://localhost:631/jobs/):
"The PPD version (5.2.11) is not compatible with Gutenprint 5.2.13.
Please run
`/nix/store/7762kpyhfkcgmr3q81v1bbyy0bjhym80-gutenprint-5.2.13/sbin/cups-genppdupdate'
as administrator."
This is due to state in "/var/lib/cups/ppd" and one would need to run
"/nix/store/.../bin/cups-genppdupdate -p /var/lib/cups/ppd" manually.
The alternative was to enable the following option:
"services.printing.gutenprint" but this had two disadvantages:
1) It is an exception that one could be unaware of or that could
potentially cause some confusion.
2) One couldn't use a customized Gutenprint derivation in
"services.printing.drivers" but would instead have to overwrite
"pkgs.gutenprint".

This new approach simply detects a Gutenprint derivation in
"services.printing.gutenprint" by checking if the meta set of a
derivation contains "isGutenprint = true". Therefore no special
exception for Gutenprint would be required and it could easily be
applied to other drivers if they would require such a script to be run.
2017-08-29 05:25:12 +04:00

393 lines
11 KiB
Nix

{ config, lib, pkgs, ... }:
with lib;
let
inherit (pkgs) cups cups-pk-helper cups-filters;
cfg = config.services.printing;
avahiEnabled = config.services.avahi.enable;
polkitEnabled = config.security.polkit.enable;
additionalBackends = pkgs.runCommand "additional-cups-backends" { }
''
mkdir -p $out
if [ ! -e ${cups.out}/lib/cups/backend/smb ]; then
mkdir -p $out/lib/cups/backend
ln -sv ${pkgs.samba}/bin/smbspool $out/lib/cups/backend/smb
fi
# Provide support for printing via HTTPS.
if [ ! -e ${cups.out}/lib/cups/backend/https ]; then
mkdir -p $out/lib/cups/backend
ln -sv ${cups.out}/lib/cups/backend/ipp $out/lib/cups/backend/https
fi
'';
# Here we can enable additional backends, filters, etc. that are not
# part of CUPS itself, e.g. the SMB backend is part of Samba. Since
# we can't update ${cups.out}/lib/cups itself, we create a symlink tree
# here and add the additional programs. The ServerBin directive in
# cupsd.conf tells cupsd to use this tree.
bindir = pkgs.buildEnv {
name = "cups-progs";
paths =
[ cups.out additionalBackends cups-filters pkgs.ghostscript ]
++ cfg.drivers;
pathsToLink = [ "/lib" "/share/cups" "/bin" ];
postBuild = cfg.bindirCmds;
ignoreCollisions = true;
};
writeConf = name: text: pkgs.writeTextFile {
inherit name text;
destination = "/etc/cups/${name}";
};
cupsFilesFile = writeConf "cups-files.conf" ''
SystemGroup root wheel
ServerBin ${bindir}/lib/cups
DataDir ${bindir}/share/cups
DocumentRoot ${cups.out}/share/doc/cups
AccessLog syslog
ErrorLog syslog
PageLog syslog
TempDir ${cfg.tempDir}
# User and group used to run external programs, including
# those that actually send the job to the printer. Note that
# Udev sets the group of printer devices to `lp', so we want
# these programs to run as `lp' as well.
User cups
Group lp
${cfg.extraFilesConf}
'';
cupsdFile = writeConf "cupsd.conf" ''
${concatMapStrings (addr: ''
Listen ${addr}
'') cfg.listenAddresses}
Listen /var/run/cups/cups.sock
SetEnv PATH /var/lib/cups/path/lib/cups/filter:/var/lib/cups/path/bin
DefaultShared ${if cfg.defaultShared then "Yes" else "No"}
Browsing ${if cfg.browsing then "Yes" else "No"}
WebInterface ${if cfg.webInterface then "Yes" else "No"}
${cfg.extraConf}
'';
browsedFile = writeConf "cups-browsed.conf" cfg.browsedConf;
rootdir = pkgs.buildEnv {
name = "cups-progs";
paths = [
cupsFilesFile
cupsdFile
(writeConf "client.conf" cfg.clientConf)
(writeConf "snmp.conf" cfg.snmpConf)
] ++ optional avahiEnabled browsedFile
++ cfg.drivers;
pathsToLink = [ "/etc/cups" ];
ignoreCollisions = true;
};
filterGutenprint = pkgs: filter (pkg: pkg.meta.isGutenprint or false == true) pkgs;
containsGutenprint = pkgs: length (filterGutenprint pkgs) > 0;
getGutenprint = pkgs: head (filterGutenprint pkgs);
in
{
###### interface
options = {
services.printing = {
enable = mkOption {
type = types.bool;
default = false;
description = ''
Whether to enable printing support through the CUPS daemon.
'';
};
listenAddresses = mkOption {
type = types.listOf types.str;
default = [ "127.0.0.1:631" ];
example = [ "*:631" ];
description = ''
A list of addresses and ports on which to listen.
'';
};
bindirCmds = mkOption {
type = types.lines;
internal = true;
default = "";
description = ''
Additional commands executed while creating the directory
containing the CUPS server binaries.
'';
};
defaultShared = mkOption {
type = types.bool;
default = false;
description = ''
Specifies whether local printers are shared by default.
'';
};
browsing = mkOption {
type = types.bool;
default = false;
description = ''
Specifies whether shared printers are advertised.
'';
};
webInterface = mkOption {
type = types.bool;
default = true;
description = ''
Specifies whether the web interface is enabled.
'';
};
extraFilesConf = mkOption {
type = types.lines;
default = "";
description = ''
Extra contents of the configuration file of the CUPS daemon
(<filename>cups-files.conf</filename>).
'';
};
extraConf = mkOption {
type = types.lines;
default = "";
example =
''
BrowsePoll cups.example.com
LogLevel debug
'';
description = ''
Extra contents of the configuration file of the CUPS daemon
(<filename>cupsd.conf</filename>).
'';
};
clientConf = mkOption {
type = types.lines;
default = "";
example =
''
ServerName server.example.com
Encryption Never
'';
description = ''
The contents of the client configuration.
(<filename>client.conf</filename>)
'';
};
browsedConf = mkOption {
type = types.lines;
default = "";
example =
''
BrowsePoll cups.example.com
'';
description = ''
The contents of the configuration. file of the CUPS Browsed daemon
(<filename>cups-browsed.conf</filename>)
'';
};
snmpConf = mkOption {
type = types.lines;
default = ''
Address @LOCAL
'';
description = ''
The contents of <filename>/etc/cups/snmp.conf</filename>. See "man
cups-snmp.conf" for a complete description.
'';
};
drivers = mkOption {
type = types.listOf types.path;
default = [];
example = literalExample "[ pkgs.gutenprint pkgs.hplip pkgs.splix ]";
description = ''
CUPS drivers to use. Drivers provided by CUPS, cups-filters,
Ghostscript and Samba are added unconditionally. If this list contains
Gutenprint (i.e. a derivation with
<literal>meta.isGutenprint = true</literal>) the PPD files in
<filename>/var/lib/cups/ppd</filename> will be updated automatically
to avoid errors due to incompatible versions.
'';
};
tempDir = mkOption {
type = types.path;
default = "/tmp";
example = "/tmp/cups";
description = ''
CUPSd temporary directory.
'';
};
};
};
###### implementation
config = mkIf config.services.printing.enable {
users.extraUsers = singleton
{ name = "cups";
uid = config.ids.uids.cups;
group = "lp";
description = "CUPS printing services";
};
environment.systemPackages = [ cups.out ] ++ optional polkitEnabled cups-pk-helper;
environment.etc."cups".source = "/var/lib/cups";
services.dbus.packages = [ cups.out ] ++ optional polkitEnabled cups-pk-helper;
# Cups uses libusb to talk to printers, and does not use the
# linux kernel driver. If the driver is not in a black list, it
# gets loaded, and then cups cannot access the printers.
boot.blacklistedKernelModules = [ "usblp" ];
systemd.packages = [ cups.out ];
systemd.services.cups =
{ wantedBy = [ "multi-user.target" ];
wants = [ "network.target" ];
after = [ "network.target" ];
path = [ cups.out ];
preStart =
''
mkdir -m 0700 -p /var/cache/cups
mkdir -m 0700 -p /var/spool/cups
mkdir -m 0755 -p ${cfg.tempDir}
mkdir -m 0755 -p /var/lib/cups
# Backwards compatibility
if [ ! -L /etc/cups ]; then
mv /etc/cups/* /var/lib/cups
rmdir /etc/cups
ln -s /var/lib/cups /etc/cups
fi
# First, clean existing symlinks
if [ -n "$(ls /var/lib/cups)" ]; then
for i in /var/lib/cups/*; do
[ -L "$i" ] && rm "$i"
done
fi
# Then, populate it with static files
cd ${rootdir}/etc/cups
for i in *; do
[ ! -e "/var/lib/cups/$i" ] && ln -s "${rootdir}/etc/cups/$i" "/var/lib/cups/$i"
done
#update path reference
[ -L /var/lib/cups/path ] && \
rm /var/lib/cups/path
[ ! -e /var/lib/cups/path ] && \
ln -s ${bindir} /var/lib/cups/path
${optionalString (containsGutenprint cfg.drivers) ''
if [ -d /var/lib/cups/ppd ]; then
${getGutenprint cfg.drivers}/bin/cups-genppdupdate -p /var/lib/cups/ppd
fi
''}
'';
serviceConfig.PrivateTmp = true;
};
systemd.services.cups-browsed = mkIf avahiEnabled
{ description = "CUPS Remote Printer Discovery";
wantedBy = [ "multi-user.target" ];
wants = [ "cups.service" "avahi-daemon.service" ];
bindsTo = [ "cups.service" "avahi-daemon.service" ];
partOf = [ "cups.service" "avahi-daemon.service" ];
after = [ "cups.service" "avahi-daemon.service" ];
path = [ cups ];
serviceConfig.ExecStart = "${cups-filters}/bin/cups-browsed";
restartTriggers = [ browsedFile ];
};
services.printing.extraConf =
''
LogLevel info
DefaultAuthType Basic
<Location />
Order allow,deny
Allow localhost
</Location>
<Location /admin>
Order allow,deny
Allow localhost
</Location>
<Location /admin/conf>
AuthType Basic
Require user @SYSTEM
Order allow,deny
Allow localhost
</Location>
<Policy default>
<Limit Send-Document Send-URI Hold-Job Release-Job Restart-Job Purge-Jobs Set-Job-Attributes Create-Job-Subscription Renew-Subscription Cancel-Subscription Get-Notifications Reprocess-Job Cancel-Current-Job Suspend-Current-Job Resume-Job CUPS-Move-Job>
Require user @OWNER @SYSTEM
Order deny,allow
</Limit>
<Limit Pause-Printer Resume-Printer Set-Printer-Attributes Enable-Printer Disable-Printer Pause-Printer-After-Current-Job Hold-New-Jobs Release-Held-New-Jobs Deactivate-Printer Activate-Printer Restart-Printer Shutdown-Printer Startup-Printer Promote-Job Schedule-Job-After CUPS-Add-Printer CUPS-Delete-Printer CUPS-Add-Class CUPS-Delete-Class CUPS-Accept-Jobs CUPS-Reject-Jobs CUPS-Set-Default>
AuthType Basic
Require user @SYSTEM
Order deny,allow
</Limit>
<Limit Cancel-Job CUPS-Authenticate-Job>
Require user @OWNER @SYSTEM
Order deny,allow
</Limit>
<Limit All>
Order deny,allow
</Limit>
</Policy>
'';
security.pam.services.cups = {};
};
}