2.6 KiB
Getting the Sources
By default, NixOS's nixos-rebuild command uses the NixOS and Nixpkgs
sources provided by the nixos channel (kept in
/nix/var/nix/profiles/per-user/root/channels/nixos). To modify NixOS,
however, you should check out the latest sources from Git. This is as
follows:
$ git clone https://github.com/NixOS/nixpkgs
$ cd nixpkgs
$ git remote update origin
This will check out the latest Nixpkgs sources to ./nixpkgs the NixOS
sources to ./nixpkgs/nixos. (The NixOS source tree lives in a
subdirectory of the Nixpkgs repository.) The nixpkgs repository has
branches that correspond to each Nixpkgs/NixOS channel (see
for more information about channels). Thus, the
Git branch origin/nixos-17.03 will contain the latest built and tested
version available in the nixos-17.03 channel.
It's often inconvenient to develop directly on the master branch, since if somebody has just committed (say) a change to GCC, then the binary cache may not have caught up yet and you'll have to rebuild everything from source. So you may want to create a local branch based on your current NixOS version:
$ nixos-version
17.09pre104379.6e0b727 (Hummingbird)
$ git checkout -b local 6e0b727
Or, to base your local branch on the latest version available in a NixOS channel:
$ git remote update origin
$ git checkout -b local origin/nixos-17.03
(Replace nixos-17.03 with the name of the channel you want to use.)
You can use git merge or git rebase to keep your local branch in sync with the channel, e.g.
$ git remote update origin
$ git merge origin/nixos-17.03
You can use git cherry-pick to copy commits from your local branch to
the upstream branch.
If you want to rebuild your system using your (modified) sources, you
need to tell nixos-rebuild about them using the -I flag:
# nixos-rebuild switch -I nixpkgs=/my/sources/nixpkgs
If you want nix-env to use the expressions in /my/sources, use
nix-env -f /my/sources/nixpkgs, or change the default by adding a symlink in
~/.nix-defexpr:
$ ln -s /my/sources/nixpkgs ~/.nix-defexpr/nixpkgs
You may want to delete the symlink ~/.nix-defexpr/channels_root to
prevent root's NixOS channel from clashing with your own tree (this may
break the command-not-found utility though). If you want to go back to
the default state, you may just remove the ~/.nix-defexpr directory
completely, log out and log in again and it should have been recreated
with a link to the root channels.