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