proc_pid_mounts(5)

💖 proc_pid_mounts — like, the manual page, bestie 💖

okay so this is a page from the File Formats Manual — it's the proc_pid_mounts(5) situation and honestly? it's giving filesystem gossip and i'm obsessed. let's get into it 🫶

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✨ NAME ✨

/proc/pid/mounts — the mounted filesystems, periodt 💅

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🌸 DESCRIPTION 🌸

🎀 /proc/pid/mounts (since Linux 2.4.19)

okay bestie, so this file right here? it lists all the filesystems currently mounted in the process's mount namespace — yes, the whole namespace thing, go check mount_namespaces(7) if you're new here 🦋

and the format of this file? it's documented in fstab(5). like, literally the exact same format. iykyk ✨

🔥 the pollable era (since Linux 2.6.15)

not me being able to poll this file 😭 since Linux 2.6.15 this file is pollable — here's the tea:

after you open the file for reading, if something changes in this file (i.e., a filesystem mount or unmount happens), then:

• select(2) marks the file descriptor as having an exceptional condition 👀
• poll(2) and epoll_wait(2) mark the file as having a priority event (POLLPRI) 💅

🕰️ throwback moment: before Linux 2.6.30, a change in this file was signalled differently — the file descriptor got marked as readable for select(2), and got marked as having an error condition for poll(2) and epoll_wait(2). different vibe, same drama 💀

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🦋 /proc/mounts

so before Linux 2.4.19, this file was just a list of all the filesystems currently mounted on the system. simple. unbothered. iconic ✨

but then per-process mount namespaces got introduced in Linux 2.4.19 (see mount_namespaces(7) — go read it 🌈), and this file became a link to /proc/self/mounts, which lists the mounts of the process's own mount namespace. main character energy only, no cap 👑

and yep, the format of this file is documented in fstab(5) too. consistency, we love to see it 💜

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⭐ SEE ALSO ⭐

• proc(5)

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and that's the whole page bestie, no notes 💖 tysm for reading, mwah 🎀

this was brought to you by Linux man-pages 6.20, dated 2026-02-08 — proc_pid_mounts(5), slay ✨🌸