75 lines
2.3 KiB
Markdown
75 lines
2.3 KiB
Markdown
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# Building Specific Parts of NixOS {#sec-building-parts}
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With the command `nix-build`, you can build specific parts of your NixOS
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configuration. This is done as follows:
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```ShellSession
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$ cd /path/to/nixpkgs/nixos
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$ nix-build -A config.option
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```
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where `option` is a NixOS option with type "derivation" (i.e. something
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that can be built). Attributes of interest include:
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`system.build.toplevel`
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: The top-level option that builds the entire NixOS system. Everything
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else in your configuration is indirectly pulled in by this option.
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This is what `nixos-rebuild` builds and what `/run/current-system`
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points to afterwards.
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A shortcut to build this is:
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```ShellSession
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$ nix-build -A system
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```
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`system.build.manual.manualHTML`
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: The NixOS manual.
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`system.build.etc`
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: A tree of symlinks that form the static parts of `/etc`.
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`system.build.initialRamdisk` , `system.build.kernel`
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: The initial ramdisk and kernel of the system. This allows a quick
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way to test whether the kernel and the initial ramdisk boot
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correctly, by using QEMU's `-kernel` and `-initrd` options:
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```ShellSession
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$ nix-build -A config.system.build.initialRamdisk -o initrd
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$ nix-build -A config.system.build.kernel -o kernel
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$ qemu-system-x86_64 -kernel ./kernel/bzImage -initrd ./initrd/initrd -hda /dev/null
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```
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`system.build.nixos-rebuild` , `system.build.nixos-install` , `system.build.nixos-generate-config`
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: These build the corresponding NixOS commands.
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`systemd.units.unit-name.unit`
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: This builds the unit with the specified name. Note that since unit
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names contain dots (e.g. `httpd.service`), you need to put them
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between quotes, like this:
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```ShellSession
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$ nix-build -A 'config.systemd.units."httpd.service".unit'
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```
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You can also test individual units, without rebuilding the whole
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system, by putting them in `/run/systemd/system`:
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```ShellSession
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$ cp $(nix-build -A 'config.systemd.units."httpd.service".unit')/httpd.service \
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/run/systemd/system/tmp-httpd.service
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# systemctl daemon-reload
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# systemctl start tmp-httpd.service
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```
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Note that the unit must not have the same name as any unit in
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`/etc/systemd/system` since those take precedence over
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`/run/systemd/system`. That's why the unit is installed as
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`tmp-httpd.service` here.
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