Having socket-activated epmd means that there always be only a single
instance managed centrally. Because Erlang also starts it
automatically if not available, and in worst case scenario 'epmd' can
be started by some Erlang application running under systemd. And then
restarting this application unit will cause complete loss of names in
'epmd' (if other Erlang system are also installed on this host).
E.g. see at which lengths RabbitMQ goes to recover from such
situations:
7741b37b1e/src/rabbit_epmd_monitor.erl (L36)
Having the only one socket-activated epmd completely solves this
problem.
This makes the command ‘nix-env -qa -f. --arg config '{skipAliases =
true;}'’ work in Nixpkgs.
Misc...
- qtikz: use libsForQt5.callPackage
This ensures we get the right poppler.
- rewrites:
docbook5_xsl -> docbook_xsl_ns
docbook_xml_xslt -> docbook_xsl
diffpdf: fixup
This adds configuration options which automate the configuration of NVIDIA Optimus using PRIME. This allows using the NVIDIA proprietary driver on Optimus laptops, in order to render using the NVIDIA GPU while outputting to displays connected only to the integrated Intel GPU. It also adds an option for enabling kernel modesetting for the NVIDIA driver (via a kernel command line flag); this is particularly useful together with Optimus/PRIME because it fixes tearing on PRIME-connected screens.
The user still needs to enable the Optimus/PRIME feature and specify the bus IDs of the Intel and NVIDIA GPUs, but this is still much easier for users and more reliable. The implementation handles both the X configuration file as well as getting display managers to run certain necessary `xrandr` commands just after X has started.
Configuration of commands run after X startup is done using a new configuration option `services.xserver.displayManager.setupCommands`. Support for this option is implemented for LightDM, GDM and SDDM; all of these have been tested with this feature including logging into a Plasma session.
Note: support of `setupCommands` for GDM is implemented by making GDM run the session executable via a wrapper; the wrapper will run the `setupCommands` before execing. This seemed like the simplest and most reliable approach, and solves running these commands both for GDM's X server and user X servers (GDM starts separate X servers for itself and user sessions). An alternative approach would be with autostart files but that seems harder to set up and less reliable.
Note that some simple features for X configuration file generation (in `xserver.nix`) are added which are used in the implementation:
- `services.xserver.extraConfig`: Allows adding arbitrary new sections. This is used to add the Device section for the Intel GPU.
- `deviceSection` and `screenSection` within `services.xserver.drivers`. This allows the nvidia configuration module to add additional contents into the `Device` and `Screen` sections of the "nvidia" driver, and not into such sections for other drivers that may be enabled.
This allows non-privileged users to configure local DNS
entries by editing hosts files read by NetworkManager's dnsmasq
instance.
Cherry-picked from e6c3d5a507909c4e0c0a5013040684cce89c35ce and
5a566004a2b12c3d91bf0acdb704f1b40770c28f.
The deep merge caused all the options to be unset when generating docs, unless quagga was enabled.
Using imports, instead, properly allows the documentation to be generated.
The `.service` file defining the `systemd` unit for `autorandr.service`
which is bundled with the package itself uses `--default default` in the
`ExecStart` section. This can be an issue when having multiple layouts
(e.g. `default` as workstation layout I mostly work on and `mobile` when
I go somewhere else).
When the service gets restarted and `--default` can't be applied,
however the current layout can't be detected (e.g. when working with an
unknown beamer) the service silently fails with a message like this:
```
Jun 22 18:44:46 hauptshuhle autorandr[3168]: /nix/store/h83b72ffm68nm8fyjnppljchp456a94r-xrandr-1.5.0/bin/xrandr: ca>
Jun 22 18:44:46 hauptshuhle autorandr[3168]: Failed to apply profile 'default' (line 718):
Jun 22 18:44:46 hauptshuhle autorandr[3168]: Command failed: /nix/store/h83b72ffm68nm8fyjnppljchp456a94r-xrandr-1.>
```
As discussed in the IRC (see https://botbot.me/freenode/nixos/2018-07-05/?msg=101791455&page=6)
it's a bad long-term solution in terms of maintenance to manually patch
the service file bundled with the derivation, instead the service shall
be configured declaratively. Additionally this makes possible overrides
from the user-space way easier.
The `udev` rule (in `$out/etc/udev/rules.d`) won't' be affected, it
simply runs `systemctl start autorandr.service` when e.g. a new display
is added, so now `udev` communicates with the NixOS systemd unit.
