SWWDOG(4)

💖 swwdog(4) — software watchdog timer 💖

okay bestie, welcome to the swwdog(4) page from the Kernel Interfaces Manual. this is the software watchdog timer, and it's lowkey the kernel's "are you still there??" bestie. no cap. ✨

🌸 NAME 🌸

swwdog — software watchdog timer. that's the whole name, periodt. 💅

✨ SYNOPSIS ✨

pseudo-device swwdog

🎀 DESCRIPTION 🎀

okay so the swwdog driver provides a software watchdog timer that works with wdogctl(8). if the timer expires, the system reboots if the boolean variable swwdog_reboot is true; otherwise, the system will panic. swwdog_reboot is accessible as the sysctl(8) variable hw.swwdog.reboot and defaults to false. 😭

The default period of swwdog is 60 seconds. yes, a whole minute — the watchdog is patient, but not that patient. 💅

As with other watchdog timers, the swwdog driver prevents a system from suspending when the watchdog is armed. so if the watchdog is armed, the system is not going to sleep on you. periodt. 🫶

🔥 SEE ALSO 🔥

• sysctl(8)
• wdogctl(8)

👑 HISTORY 👑

The swwdog driver was written by Steven M. Bellovin. iconic author behavior, honestly. 🫶

💀 BUGS 💀

• Only one watchdog timer can be active at any given time. (Arguably, this is a bug in the watchdog timer framework.) Therefore, only a single instance of the swwdog device can be created. so yeah, one at a time, bestie.
• Kernel tickle mode is useless with swwdog and arguably should be rejected, since both it and this driver rely on the same callout mechanism; if one is blocked, almost certainly the other is as well.
• The alarm option to wdogctl(8) isn't implemented.

mwah 💋 — this page is from Debian, dated June 8, 2011. hope that helped bestie 🫶✨