Commit fe8ff02 adds a ‘guix-gc’ command to invoke the GC, similar to part of the ‘nix-store’ command. Below is a copy of the manual.
Comments welcome! Ludo’. Packages that are installed but not used may be "garbage-collected". The `guix-gc' command allows users to explicitly run the garbage collector to reclaim space from the `/nix/store' directory. The garbage collector has a set of known "roots": any file under `/nix/store' reachable from a root is considered "live" and cannot be deleted; any other file is considered "dead" and may be deleted. The set of garbage collector roots includes default user profiles, and may be augmented with `guix-build --root', for example (*note Invoking guix-build::). The `guix-gc' command has three mode of operations: it can be used to garbage-collect any dead files (the default), to delete specific files (the `--delete' option), or to print garbage-collector information. The available options are listed below: `--collect-garbage[=MIN]' `-C [MIN]' Collect garbage--i.e., unreachable `/nix/store' files and sub-directories. This is the default operation when no option is specified. When MIN is given, stop once MIN bytes have been collected. MIN may be a number of bytes, or it may include a unit as a suffix, such as `MiB' for mebibytes and `GB' for gigabytes. When MIN is omitted, collect as much garbage as possible. `--delete' `-d' Attempt to delete all the store files and directories specified as arguments. This fails if some of the files are not in the store, or if they are still live. `--list-dead' Show the list of dead files and directories still present in the store--i.e., files and directories no longer reachable from any root. `--list-live' Show the list of live store files and directories.