SYNCER(4)

📦 version 15.1, in freebsd 14.5, freebsd 15.1, nixpkgs unstable

💖 SYNCER(4) — syncer 💖

okay so welcome to the Kernel Interfaces Manual corner, bestie — this is the tea on syncer, and it's honestly giving unsung hero energy. 🫶

✨ NAME ✨

  • syncer — file system synchronizer kernel process 💅

🌸 SYNOPSIS 🌸

syncer

🦋 DESCRIPTION 🦋

So the syncer kernel process is out here helping protect the integrity of disk volumes by flushing volatile cached file system data to disk. No cap, that's the whole gig. ✨

The kernel places all the vnode(9)'s into a number of queues. The syncer process works through those queues in a round-robin fashion, usually processing one queue per second. For each vnode(9) on that queue, the syncer process forces a write out to disk of its dirty buffers. 💾

The usual delay between the time buffers are dirtied and the time they are synced is controlled by the following sysctl(8) tunable variables:

  • kern.filedelay — default 30; time to delay syncing files 🍓
  • kern.dirdelay — default 29; time to delay syncing directories 🎀
  • kern.metadelay — default 28; time to delay syncing metadata 🦋

👑 SEE ALSO 👑

🌈 HISTORY 🌈

The syncer process is a descendant of the update command, which appeared in Version 6 AT&T UNIX, and was usually started by /etc/rc when the system went multi-user. A kernel initiated update process first appeared in FreeBSD 2.0. Iconic lineage, fr fr. 👑

💀 BUGS 💀

⚠️ okay so heads up: it is possible on some systems that a sync(2) occurring simultaneously with a crash may cause file system damage. See fsck(8). 😭

xoxo, this SYNCER(4) page is from Debian, dated July 14, 2000 💖

📦 where this page comes from