* Update attribute names in code examples (* -> settings.*).
* Use `nix-shell -p` rather than `nix run` because the example won't
work with the current default Nix.
* Update config values for `element-web`.
* Fix link to `element-web` security considerations.
* Make the synapse expression even smaller and use callout-lists to
explain the code.
* Document how to correctly deploy the shared registration secret.
[1] https://spec.matrix.org/latest/client-server-api/#getwell-knownmatrixclient
Potential use cases for disabling `useDefaultFilesystems` include:
- Testing with uncommon filesystem layouts
- Testing scenarios where swapping occurs
- Testing with LUKS-encrypted disks
Closes#177963
Running `nixos/tests/keepassxc.nix` shows:
```
machine # [ 18.705390] xsession[985]: /nix/store/2g2jx5c6x3p152wbiijr0rmky7byqivc-xsession: line 13: nn: command not found
```
This garbled bash script runs without `set -o errexit` and thus skips
"\n\n" as invalid command:
```
$ cat -n /nix/store/2g2jx5c6x3p152wbiijr0rmky7byqivc-xsession
...
\n\n
if [ -e $HOME/.background-image ]; then
/nix/store/wq1d1ph8wj4alpx78akvpbd0a0m9qkd1-feh-3.8/bin/feh --bg-scale $HOME/.background-image
fi
...
```
KeePassXC uses it through
`nixos/modules/services/x11/display-managers/default.nix`:
```
...
# Script responsible for starting the window manager and the desktop manager.
xsession = dm: wm: pkgs.writeScript "xsession" ''
#! ${pkgs.bash}/bin/bash
# Legacy session script used to construct .desktop files from
# `services.xserver.displayManager.session` entries. Called from
# `sessionWrapper`.
# Start the window manager.
${wm.start}
# Start the desktop manager.
${dm.start}
...
'';
...
```
The bogus line was introduced in PR #160752:
```
commit 0bc0dc8090
Author: Shaw Vrana <shaw@vranix.com>
Date: Fri Feb 18 11:27:42 2022 -0800
desktop manager script: start properly
Adds a missing line feed when X is enabled to the start script name
and the appended if check. Resolves#160735
```
I have not tried to reproduce the original issue and thus don't know
why "\n\n" apparently gets interpreted fine in one place but remains
literal the `xsession` case.
However, using a literal newline must be valid for all cases and
certainly fixes the warning seen in KeePassXC tests.
Furthermore, starting the nix string (`''`) with a newline as usual also
fixes its overall indentation.
Seems silly to install this for use with the local server, but to not
configure it to use the local server. Otherwise, out of the box we
just get an error about no server being configured.
