34435a9502
Before commit 54fa0cfe4eef7e54e23380704af70ee7b65473ce, the `redshift`
service was run with the environment variable `DISPLAY` set to `:0`.
Commit 54fa0cfe4eef7e54e23380704af70ee7b65473ce changed this to
instead use the value of the `services.xserver.display` configuration
option in the value of the `DISPLAY` variable. In so doing, no default
value was provided for the case where `services.xserver.display` is
`null`.
While the default value of `services.xserver.display` is `0`, use of
which by the `redshift` module would result in `DISPLAY` again being
set to `:0`, `services.xserver.display` may also be `null`, to which
value it is set by, e.g., the `lightdm` module.
In the case that `services.xserver.display` is `null`, with the change
made in commit 54fa0cfe4eef7e54e23380704af70ee7b65473ce, the `DISPLAY`
variable in the environment of the `redshift` service would be set to
`:` (a single colon), which, according to my personal experience,
would result in —
- the `redshift` service failing to start; and
- systemd repeatedly attempting to restart the `redshift` service,
looping indefinitely, while the hapless `redshift` spews error
messages into the journal.
It can be observed that the malformed value of `DISPLAY` is likely at
fault for this issue by executing the following commands in an
ordinary shell, with a suitable `redshift` executable, and the X11
display not already tinted:
- `redshift -O 2500` — This command should reduce the color
temperature of the display (making it more reddish).
- `DISPLAY=':' redshift -O 6500` — This command should raise the
color temperature back up, were it not for the `DISPLAY`
environment variable being set to `:` for it, which should cause
it to, instead, fail with several error messages.
This commit attempts to fix this issue by having the `DISPLAY`
environment variable for the `redshift` service default to its old
value of `:0` in the case that `services.xserver.display` is `null`.
I have tested this solution on NixOS, albeit without the benefit of a
system with multiple displays.
Nixpkgs is a collection of packages for the Nix package manager. It is periodically built and tested by the hydra build daemon as so-called channels. To get channel information via git, add nixpkgs-channels as a remote:
% git remote add channels git://github.com/NixOS/nixpkgs-channels.git
For stability and maximum binary package support, it is recommended to maintain
custom changes on top of one of the channels, e.g. nixos-16.03 for the latest
release and nixos-unstable for the latest successful build of master:
% git remote update channels
% git rebase channels/nixos-16.03
For pull-requests, please rebase onto nixpkgs master.
NixOS linux distribution source code is located inside
nixos/ folder.
- NixOS installation instructions
- Documentation (Nix Expression Language chapter)
- Manual (How to write packages for Nix)
- Manual (NixOS)
- Nix Wiki (deprecated, see milestone "Move the Wiki!")
- Continuous package builds for unstable/master
- Continuous package builds for 16.03 release
- Tests for unstable/master
- Tests for 16.03 release
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