This commit adds the options --build-host and --target-host to nixos-rebuild.
--build-host instructs nixos-rebuild to perform all nix builds on the
specified host (via ssh). Build results are then copied back to the
local machine and used when activating the system.
--build-target instructs nixos-rebuild to activate the configuration
not on the local machine but on the specified remote host. Build
results are copied to the target machine and then activated there (via ssh).
It is possible to combine the usage of --build-host and --target-host,
in which case you can perform the build on one remote machine and deploy
the configuration to another remote machine. The only requirement is that
the build host has a working ssh connection to the target host (if the
target is not local), and that the local machine can connect to both
the target and the build host. Also, your user must be allowed to copy
nix closures between the local machine and the target and host machines.
At no point in time are the configuration sources (the nix files) copied
anywhere. Instead, nix evaluation always happens locally
(with nix-instantiate). The drv-file is then copied and realised remotely
(with nix-store).
As a convenience, if only --target-host is specified, --build-host is
implicitly set to that host too. So if you want to build locally and deploy
remotely you have to explicitly set "--build-host localhost".
To activate (test, boot or switch) you need to have root access to the
target host. You can specify this by "--target-host root@myhost".
I have tested the obvious scenarios and they are working. Some of the
combinations of --build-host and --target-host and the various actions might
not make much sense, and should maybe be forbidden (like setting a remote
target host when building a VM), and some combinations might not work at all.
This partially reverts commit 3a4fd0bfc6.
Addresses another concern by @edolstra that users might not want to
update *all* channels. We're now reverting to the old behaviour but
after updating the "nixos" channel, we just check whether the channel
ships with a file called ".update-on-nixos-rebuild" and if it exists, we
update that channel as well.
Other channels than these are not touched anymore.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Should make it even easier to use custom channels, because whenever the
user does a "nixos-rebuild --upgrade", it will also upgrade possibly
used ("used" as in referenced in configuration.nix) channels besides
"nixos". And if you also ship a channel tied to a particular version of
nixpkgs or even remove the "nixos" channels, you won't run into
unexpected situations where the system is not updating your custom
channels.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
‘nixos-rebuild dry-activate’ builds the new configuration and then
prints what systemd services would be stopped, restarted etc. if the
configuration were actually activated. This could be extended later to
show other activation actions (like uids being deleted).
To prevent confusion, ‘nixos-rebuild dry-run’ has been renamed to
‘nixos-rebuild dry-build’.
Previously, if the currently installed Nix is too old to evaluate
Nixpkgs, then nixos-rebuild would fail and the user had to upgrade Nix
manually. Now, as a fallback, we run ‘nix-store -r’ to obtain a binary
Nix directly from the binary cache.
This allows doing any necessary actions that were not in the installed
nixos-rebuild (such as downloading a new version of Nix). This does
require us to be careful that nixos-rebuild is backwards-compatible
(i.e. can run in any old installation).
Commit 31203732b3 dropped the reference to
<nixos> from NIX_PATH (nixos/modules/programs/environment.nix) and thus
prevents systems that are not using channels from rebuilding.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
