watchdog_write(9)

📦 version 7.3.1, in nixpkgs unstable

💖 watchdog_write(9) — okay so this is the Kernel API Manual, bestie ✨

Like, hi, welcome to the watchdog_write(9) page — it's giving "tiny function, big responsibility" and honestly? Iconic. 🐕🫶

🌸 NAME 🌸

watchdog_write — literally writes to the watchdog, that's it, that's the whole vibe 💅

✨ SYNOPSIS ✨

ssize_t watchdog_write (struct file *file , const char __user *data ,
       size_t len , loff_t *ppos );

Look at her. Four args, one ssize_t return, main character energy fr fr 👑

🎀 ARGUMENTS 🎀

Ok bestie, here's who's who in the group chat:

  • file — the File from VFS. She's the one who showed up from the virtual filesystem, no cap.
  • data — user address of data. Yes, user address — behave yourself 🙈
  • len — length of data. How much we're working with, periodt.
  • ppos — pointer to the file offset. Little pointer, big job 💫

🦋 DESCRIPTION 🦋

So here's the tea ☕: a write to a watchdog device is defined as a keepalive ping. That's the whole definition — writing here = "hey bestie I'm still alive" 💖

And the spicy part? Writing the magic 'V' sequence allows the next close to turn off the watchdog — but ONLY if 'nowayout' is not set. So if 'nowayout' IS set, that door is closed, no takebacks, lowkey permanent 🌈

Careful pookie: that 'V' magic sequence is a whole mood shift — it arms the next close to actually shut the watchdog down. If 'nowayout' is set, that off-switch stays off-limits. Know before you write 🫶

⭐ RETURN ⭐

len if successful, error otherwise. That's it. Slay or fail, no in-between 💀

💜 SEE ALSO 💜

Kernel file ./drivers/watchdog/watchdog_dev.c — go read the source bestie, iykyk 🔥

And the whole watchdog friend group, all together in one big SE ALSO reunion:

🧚 Sign-off, mwah 🧚

This whole page comes to you courtesy of ./drivers/watchdog, dated October 2026 — so like, remember where she came from 🎀 Byeee, go ping your watchdog and stay hydrated 💖✨🌸

📦 where this page comes from