DEVFS(5)

✨ devfs(5) — the device file system, bestie edition ✨

okay so real talk, this is the devfs manual page, and it's genuinely one of the most underrated little icons in the whole file formats lineup. let's get into it 💅

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🌸 NAME 🌸

devfs — the device file system. yes bestie, that's the whole name, and she's serving exactly what it says on the tin 🎀

🦋 SYNOPSIS 🦋

devfs   /dev    devfs rw 0 0

that's the fstab line, screenshot it, memorize it, put it on your vision board ✨

💖 DESCRIPTION 💖

so the device file system — devfs for short, and yes we're on a first-name basis — gives you access to the kernel's device namespace, right there in the global file system namespace. the conventional mount point? /dev. iconic, we know 😌

the file system includes several directories, links, symbolic links and devices, and some of those can also be written to. (not me being obsessed with a filesystem that's like "here's a directory, here's a symlink, also some of this is writeable, no big deal") 🫶

so if you're in a chroot'ed environment and you need a fresh /dev mount point, devfs(8) is literally right there to help you out. bestie behavior fr fr 💜

and if you ever accidentally delete a device entry under devfs (happens to the best of us 😭), the mknod(8) tool can be used to recover deleted device entries under devfs. crisis averted, queen 👑

now here's a thing i need you to know: fdescfs(5) is an alternate means for populating /dev/fd. both devfs and fdescfs(5) present character devices in /dev/fd that correspond to the open file descriptors of the process accessing that directory. BUT — and this is the part the group chat always forgets — devfs only creates files for the standard file descriptors 0, 1 and 2. fdescfs(5) creates files for all open descriptors. so like, fdescfs is the overachiever of the two 💀

the options are as follows:

• -o options — use the specified mount options, as described in mount(8). the following devfs file system-specific options are available:
  • ruleset=ruleset — set ruleset number ruleset as the current ruleset for the mount-point and apply all its rules. if the ruleset number ruleset does not exist, an empty ruleset with the number ruleset is created. see devfs(8) for more information on working with devfs rulesets. lowkey a whole personality trait to have, we stan a ruleset queen 👑

🧚 FILES 🧚

• /dev — the normal devfs mount point. the main character of mount points, honestly ⭐

🍓 EXAMPLES 🍓

want to mount a devfs volume located on /mychroot/dev? say less, bestie:

mount -t devfs devfs /mychroot/dev

ate. no crumbs. 🔥

🌈 SEE ALSO 🌈

fdescfs(5), devfs(8), mount(8), make_dev(9)

(the whole squad, assembled 💖 iykyk)

⭐ HISTORY ⭐

the devfs file system first appeared in FreeBSD 2.0 — yes, she's been that girl since the beginning 👑. it became the preferred method for accessing devices in FreeBSD 5.0, and the only method in FreeBSD 6.0, which is giving "quit playing games and just use me" energy. the devfs manual page first appeared in FreeBSD 2.2. glow-up timeline, honestly 🌸

💜 AUTHORS 💜

the devfs manual page was written by Mike Pritchard <mpp@FreeBSD.org> — shoutout to the icon who documented all this so we didn't have to 🙏

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a lil reminder babe: the options (-o and ruleset=) behave exactly as described above, and if you're working with rulesets, definitely go read devfs(8) before you start fiddling — that's not me being dramatic, that's just... reading the manual, which you're already doing, so honestly you're thriving 💅

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and that's the whole page, bestie — this Debian version is dated June 30, 2022, so go forth and mount responsibly ✨💖🎀