Document Derivations and Deriving Paths #12290
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And get rid of "store derivation" nonsense.
It is not a language topic.
roberth
reviewed
Jan 19, 2025
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| So far, we have covered "inert" [store objects][store object]. | ||
| But the point of the Nix store layer is to be a build system. |
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Did we? Not sure how the reader lands here. I guess we could make So far a link, but how about:
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| So far, we have covered "inert" [store objects][store object]. | |
| But the point of the Nix store layer is to be a build system. | |
| Besides functioning as a [content addressed store] the Nix store layer works as a [build system]. |
(my links and link targets need work, sorry)
doc/manual/source/store/drv.md
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| ### `__structuredAttrs` | ||
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| Historically speaking, most users of Nix made GNU Bash with a script the command run, regardless of what they were doing. |
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I am just going to delete this, because it is too explanation-y, and there are langauge docs we can move to store docs for this (in a subsequent PR!).
Ericson2314
commented
Jan 20, 2025
Thanks!! Co-authored-by: Robert Hensing <[email protected]>
Ericson2314
commented
Jan 20, 2025
| Each input must be [realised] prior to building the derivation in question. | ||
| At that point, the derivation can be *normalized*, by replacing each input deriving path with its store path --- which we now know since we've realised it. | ||
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| ## Builder Execution |
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This section is taken from the language derivation docs with no modification but link updates. It is moved here.
More can be written, but this will do for now.
It is too much of an explanation. There are other docs we can move here later in the language section already.
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This pull request has been mentioned on NixOS Discourse. There might be relevant details there: https://discourse.nixos.org/t/2024-01-20-nix-team-meeting-minutes-209/59119/1 |
Ericson2314
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Jan 20, 2025
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| ## Processing outputs | ||
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| If the builder exited successfully, the following steps happen in order to turn the output directories left behind by the builder into proper store objects: | ||
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| - **Normalize the file permissions** | ||
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| Nix sets the last-modified timestamp on all files | ||
| in the build result to 1 (00:00:01 1/1/1970 UTC), sets the group to | ||
| the default group, and sets the mode of the file to 0444 or 0555 | ||
| (i.e., read-only, with execute permission enabled if the file was | ||
| originally executable). Any possible `setuid` and `setgid` | ||
| bits are cleared. | ||
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| > **Note** | ||
| > | ||
| > Setuid and setgid programs are not currently supported by Nix. | ||
| > This is because the Nix archives used in deployment have no concept of ownership information, | ||
| > and because it makes the build result dependent on the user performing the build. | ||
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| - **Calculate the references** | ||
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| Nix scans each output path for | ||
| references to input paths by looking for the hash parts of the input | ||
| paths. Since these are potential runtime dependencies, Nix registers | ||
| them as dependencies of the output paths. | ||
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| Nix also scans for references to other outputs' paths in the same way, because outputs are allowed to refer to each other. | ||
| If the outputs' references to each other form a cycle, this is an error, because the references of store objects much be acyclic. |
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OK actually this part was reworked a little bit
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Added this heading
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Flipped the order of the two bullets
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Made part of the first one a Note
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Added the second paragraph to the second about output references
Ericson2314
requested review from
fricklerhandwerk and
edolstra
as code owners
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Motivation
Continue documenting the store layer
Context
Some material pulled from #6877
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