Skip to content

README.md

Latest commit

 

History

History
85 lines (64 loc) · 3.26 KB

README.md

File metadata and controls

85 lines (64 loc) · 3.26 KB
Raw

Running oans on a schedule (systemd)

These two template units turn oans into a set-and-forget background job: pick a directory tree once, then let a timer re-deduplicate it (weekly by default), picking up only what changed since last time.

They lean on the self-describing hashfile — a normal run records its options, paths and excludes in the hashfile, so the scheduled run only needs to name that file (oans --hashfile=FILE).

Install

If you built from source:

sudo make install-systemd          # installs both units (see the note on paths)

Or copy them by hand into your system unit directory (usually /usr/lib/systemd/system or /etc/systemd/system) and run sudo systemctl daemon-reload.

The unit ships with ExecStart=/usr/bin/oans …. make install-systemd rewrites that to wherever the binary actually lands ($(PREFIX)/bin/oans). If you install the units by hand and oans is elsewhere, edit ExecStart.

Set up a job

Give the job a short name (here media) and do the first run yourself, naming the tree and any options you want — this creates the hashfile and records the configuration the timer will replay:

sudo install -d -m 0755 /var/cache/oans
sudo oans -dr --hashfile=/var/cache/oans/media.hash /srv/media

Include -d in this run. The timer replays whatever this one recorded, so seeding with a read-only preview gives you a job that hashes weekly and never deduplicates — exit 0, 0 B reclaimed, indistinguishable from a healthy run. A replay in that state warns and prints the command that fixes it.

Then enable the timer for that job:

sudo systemctl enable --now [email protected]

That's it. Every week oans re-scans /srv/media, hashes only changed/new files, and deduplicates. To change what a job does, just re-run the setup command with new paths/options — the hashfile remembers the latest.

Operate

systemctl list-timers 'oans@*'            # when each job next runs
systemctl start [email protected]        # run one now, out of band
journalctl -u [email protected]          # see what a run did
oans --history --hashfile=/var/cache/oans/media.hash   # reclaimed-over-time

Tuning

  • Frequency: sudo systemctl edit [email protected] and override OnCalendar= (e.g. daily, Mon *-*-* 03:00:00). Per-job overrides work because each instance is its own unit.
  • Politeness: the service already runs at Nice=19 / IOSchedulingClass=idle so it yields to interactive work. Override with systemctl edit if needed.
  • Read-only report instead of dedupe: set the job up without -d (oans -r --hashfile=…) and the scheduled runs will only refresh hashes and report, never change data.

Notes

  • The service runs as root so it can read and re-extent files anywhere in the configured tree. It does no path sandboxing for that reason.
  • Deduplication only ever adjusts extent sharing through the kernel's byte-verified FIDEDUPERANGE ioctl, so an interrupted run can waste work but never corrupt data.
  • The hashfile under /var/cache/oans is just a cache; deleting it only forces the next run to re-hash from scratch.