GnosticStreetSweeperGnosticStreetSweeper@mastodon.zip
Jun 28, 2026, 2:33 AM@argv_minus_one @nixCraft what about file representation of physical devices and processes a lá /proc /sys and /dev?
Replies
ARGVMI~1.PIFargv_minus_one@mastodon.sdf.orgJun 28, 2026, 3:41 AM
Jun 28, 2026, 8:13 AM@argv_minus_one @GnosticStreetSweeper @nixCraft
They also have /proc, but not /sys. Linux’s sysfs serves largely the same purpose as sysctl on BSDs, but sysctl has a few benefits:
- It’s structured and the types are introspectable (nodes also expose human-readable descriptions). The command-line tool that exposes them for scripting can provide the structure to scripts.
- Reading or writing one is a single system call, not an open, read/write, close sequence.
- They don’t look like files, so don’t fail in weird ways (e.g. requiring reads of specific sizes).
- They don’t consume a file descriptor.
Their one disadvantage is that they don’t automatically benefit from file-namespace sandboxing tools. On FreeBSD, for example, there’s an allow list for sysctls that can be used in Capsicum capability mode but there’s no way of adding a sysctl to that list.
Norman Wilsonoclsc@mstdn.caJun 28, 2026, 3:12 PM@david_chisnall @argv_minus_one @GnosticStreetSweeper @nixCraft /sys does stuff similar to BSD sysctl, but in a much finer-grained way.
Interestingly, Linux sysctl maps directly onto /proc/sys: sysctl kernel.broken.stuff == /proc/sys/kernel/broken/stuff. The sysctl command is still a cleaner higher-level interface.