Specifying flake inputs¶

Tip

After changing your flake inputs, make sure you can rebuild your IOC with nix build -L, and re-generate your RELEASE.local file by running epicsConfigurePhase inside a development shell.

Point a flake input to a specific branch or tag¶

To make a flake input point to a specific Git branch, edit your inputs in flake.nix, and specify the branch in the URL.

GitHub¶

To specify the Git branch or tag in a GitHub URL, the format is github:owner/repo/branch-or-tag-or-revision.

For example:

Setting the EPNix release branch¶

  inputs.epnix.url = "github:epics-extensions/EPNix/nixos-25.05";

Generic SSH repository¶

For an SSH repository, the format is git+ssh://git-server/path/to/repo?ref=revision.

Tip

The ref URL parameter here means “reference,” as in a Git reference, which can be a branch name or a tag.

It’s different from the rev parameter.

For example:

Setting the branch of a GitLab SSH repo¶

  inputs.myInput.url = "git+ssh://git@my-gitlab.com/EXAMPLE/myInput.git?ref=myBranch";

Point a flake input to a specific commit¶

To make a flake input point to a specific Git commit (also called revision), edit your inputs in flake.nix, and specify the revision in the URL.

This will make sure that this input is never updated and will stay at the given revision.

GitHub¶

To specify the Git revision in a GitHub URL, the format is github:owner/repo/branch-or-tag-or-revision.

For example:

Fixing the EPNix revision¶

  inputs.epnix.url = "github:epics-extensions/EPNix/e040bcef0197ef2d39ab3313cf2bb1f00f61f582";

Generic SSH repository¶

For an SSH repository, the format is git+ssh://git-server/path/to/repo?rev=revision.

Tip

The rev URL parameter here means “revision”, as in a Git revision, which must be a commit hash.

It’s different from the ref parameter.

For example:

Fixing a GitLab SSH repo¶

  inputs.myInput.url = "git+ssh://git@my-gitlab.com/EXAMPLE/myInput.git?rev=e040bcef0197ef2d39ab3313cf2bb1f00f61f582";

By reading the lockfile¶

To find out what locked URL Nix uses, you can run nix flake metadata.

$ nix flake metadata

Resolved URL:  git+file:///home/.../myTop
Description:   My super exciting EPICS top
Path:          /nix/store/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-source
Revision:      ...
Last modified: 2025-04-24 16:23:33
Fingerprint:   ...
Inputs:
├───epnix: github:epics-extensions/EPNix/e040bcef0197ef2d39ab3313cf2bb1f00f61f582?narHash=sha256-FBCWeE/tanyKgdwr58o9w%2BKBqQaECMxgwvPuQRDu3zM%3D (2024-02-07 13:50:07)
│   ├───...
│   └───nixpkgs: github:NixOS/nixpkgs/70bdadeb94ffc8806c0570eb5c2695ad29f0e421?narHash=sha256-LWvKHp7kGxk/GEtlrGYV68qIvPHkU9iToomNFGagixU%3D (2024-01-03 14:06:54)
├───...
└───mySupportTop: git+ssh://git@my-gitlab.com/EXAMPLE/mySupportTop.git?ref=refs/heads/main&rev=3d3e3c0fe0aa5d0eaf54ee1b6d019431ae8b6bfa (2024-04-29 11:06:12)
    └───...

You can use these URLs in your flake.nix, to prevent updating your flake input by accident.

Updating flake inputs¶

See Dependency updates.