A more discerning cousin of nix-collect-garbage, mostly intended as a
testbed to allow experimentation with more advanced selection processes.
Developers and users who make use of a lot of packages ephemerally end up
with a large nix store full of packages which may or may not be used
again in the near future, but aren't referenced from a GC-root. While
nix-collect-garbage's --max-freed option is handy here, it still
selects which paths to delete at random.
nix-heuristic-gc uses a greedy algorithm to prefer deletion of less-recently
accessed (or more easily replaceable) store paths.
- Since we're unable to hold nix's garbage-collection lock between calls to discover unreachable store paths and then request deletion of them, it's possible we may request deletion of paths that are no longer unreachable.
- Whether a path is "recently used" is determined using atime, which is far from perfect and may even be disabled on your filesystem.
- This may not work (at all) well with both
keep-derivationsandkeep-outputsnix settings enabled. - This is unable to delete invalid paths (i.e. the partial products of failed builds) because libnixstore lacks the interface to precisely request such a thing.
- If it breaks, you get to keep both parts. That said, there shouldn't be any real danger of e.g. deleting something that the existing GC wouldn't delete as we effectively just wrap the existing GC commands at a cpp-level.
usage: nix_heuristic_gc [-h]
[--penalize-drvs | --no-penalize-drvs | --penalize-drvs-weight WEIGHT]
[--penalize-substitutable | --no-penalize-substitutable | --penalize-substitutable-weight WEIGHT]
[--penalize-inodes | --no-penalize-inodes | --penalize-inodes-weight WEIGHT]
[--penalize-size | --no-penalize-size | --penalize-size-weight WEIGHT]
[--penalize-exceeding-limit | --no-penalize-exceeding-limit | --penalize-exceeding-limit-weight WEIGHT]
[--inherit-atime | --no-inherit-atime] [--dry-run | --no-dry-run]
[--threads THREADS] [--version] [--verbose | --quiet]
limit
delete the least recently used or most easily replaced nix store paths based on customizable
heuristics
positional arguments:
limit Amount of garbage to collect, specified either in units of bytes (with
optional multiplier prefix) or in units of 'I' (uppercase) - the number
of inodes to be freed. Numbers with no units are assumed to be bytes.
E.g. '100MiB' - 100 Mebibytes, '12KI' - 12 thousand inodes, '2G' - 2
Gigabytes
options:
-h, --help show this help message and exit
--penalize-drvs
--no-penalize-drvs
--penalize-drvs-weight WEIGHT
Prefer choosing .drv paths for deletion, with weighting WEIGHT
typically being a value from 1 (weak) to 10 (strong). --penalize-drvs
flag applies a WEIGHT of 5. .drv files are usually easily regenerated
and occupy an inode each.
--penalize-substitutable
--no-penalize-substitutable
--penalize-substitutable-weight WEIGHT
Prefer choosing paths for deletion that are substitutable from a binary
cache, with weighting WEIGHT typically being a value from 1 (weak) to
10 (strong). --penalize-substitutable flag applies a WEIGHT of 5. On by
default, this can slow down the path selection process for large
collections due to the mass querying of binary cache(s).
--penalize-inodes
--no-penalize-inodes
--penalize-inodes-weight WEIGHT
Prefer choosing paths for deletion that will free up a lot of inodes,
with weighting WEIGHT typically being a value from 1 (weak) to 10
(strong). --penalize-inodes flag applies a WEIGHT of 5. When specifying
a deletion limit by number of inodes, this will tend to select fewer,
more inode-heavy paths to reach that limit - but it can be prone to
overshoot, so recommend use with --penalize-exceeding-limit in this
case..
--penalize-size
--no-penalize-size
--penalize-size-weight WEIGHT
Prefer choosing larger (by nar size) paths for deletion, with weighting
WEIGHT typically being a value from 1 (weak) to 10 (strong).
--penalize-size flag applies a WEIGHT of 5. When specifying a deletion
limit in bytes, this will tend to select fewer, larger paths to reach
that limit - but it can be prone to overshoot, so recommend use with
--penalize-exceeding-limit in this case..
--penalize-exceeding-limit
--no-penalize-exceeding-limit
--penalize-exceeding-limit-weight WEIGHT
Attempt to avoid going significantly over the size limit, with
weighting WEIGHT typically being a value from 1 (weak) to 10 (strong).
--penalize-exceeding-limit flag applies a WEIGHT of 5. This penalizes
path selections that would cause more deletion than requested by limit
proportional to the overshoot.
--inherit-atime, --no-inherit-atime
Whether recent-usage calculations should take into account recent usage
of referring paths. The idea of this being to avoid removal of packages
which may not *themselves* have been accessed recently, but may still
have been required by a path that *was* accessed recently. This can
only use information from paths that still exist at time of invocation,
so repeated calls for small deletions will produce less accurate
results than a single call for a larger deletion which has more
information to work with. (default: False)
--dry-run, --no-dry-run
Don't actually delete any paths, but print list of paths that would be
deleted to stdout. (default: False)
--threads THREADS, -t THREADS
Maximum number of threads to use when gathering path information. 0
disables multi-threading entirely. Default automatic. Concurrency is
also limited by store settings' max-connections value - for best
results increase that to a sensible value (perhaps via NIX_REMOTE?).
--version show program's version number and exit
--verbose, -v
--quiet, -q