Having fixed the Google Compute Engine image build process's copying
of store paths in PR #24264, I ran `nixos-rebuild --upgrade switch`...
and the GCE image broke again, because it sets the NixOS configuration
option for the sysctl variable `kernel.yama.ptrace_scope` to
`mkDefault "1"`, i.e., with override priority 1000, and now the
`sysctl` module sets the same option to `mkDefault "0"` (this was
changed in commit 86721a5f78).
This patch raises the override priority of the Google Compute Engine
image configuration's definition of the Yama sysctl option to 500
(still lower than the priority of an unmodified option definition).
I have tested that this patch allows the Google Compute Engine image
to again build successfully for me.
And adopt the tests to add an interface and remove it again.
It should work when deactivating rstp, it will not work when activating
rstp for the first bridge as then the userspace daemon is not yet
available. But once one bridge is active with stp, it should work with
the reload for any further bridge.
Fixes#21745. Also see #22547.
Currently, if you try to build a NixOS config including channel.nix, e.g.:
nix-build -I nixpkgs=. -I nixos-config=nixos/modules/installer/cd-dvd/installation-cd-minimal.nix nixos -A config.system.build.isoImage
twice in a row, you end up with two different build results. This is
caused by the 'result' symlink of the first build affecting the channel
contents of the second build.
If we use filterSource with a predicate that ignores the 'result'
symlinks, the problem is gone. Do the same thing for VIM/Emacs
swap/backup files to avoid even more 'spurious' rebuilds.
Additionally, filter out the '.git' directory at the same time, as we
'rm -rf' it from the result anyway. This avoids a considerable amount of
unnecessary file I/O copying and deleting the .git directory.
In `nixos/modules/virtualisation/google-compute-image.nix`, copy store
paths with `rsync -a` rather than `cp -prd`, because `rsync` seems
better able to handle the hard-links that may be present in the store,
whereas `cp` may fail to copy them.
I have tested that the Google Compute Engine image builds successfully
for me with this patch, whereas it did not without this patch.
This is the same fix applied for Azure images in commit
097ef6e435.
Fixes#23973.
The inability to run strace or gdb is the kind of
developer-unfriendliness that we're used to from OS X, let's not do it
on NixOS.
This restriction can be re-enabled by setting
boot.kernel.sysctl."kernel.yama.ptrace_scope" = 1;
It might be nice to have a NixOS module for enabling hardened defaults.
Xref #14392.
Thanks @abbradar.
