mntui

11/7/2025

mntui - Simple UI for FSTAB in Linux

I wanted to democratize mount management in Linux and sometimes you just need a tool that doesn’t care about your distro, your init system, or whatever’s half-working around you. mntui is that kind of tool - a minimal, trusted mount utility that reads straight from the kernel and edits your /etc/fstab safely, without bringing any friends.

It should run the same on a polished workstation or in a panic shell with only busybox and hope.

What I started with

I wanted a mount manager that doesn’t depend on anything else - no util-linux, no systemd, no dynamic libraries quietly missing at the worst possible time.

Just a single static binary that:

• Lists what’s mounted right now (via /proc/self/mountinfo)
• Reads and validates /etc/fstab
• Lets you mount, unmount, and test entries safely
• Works even when /usr isn’t mounted yet

That’s it. Simple enough to trust. Portable enough to live on a rescue USB.

Ohh ‘kay, why though?

Most systems today assume the rest of userspace is intact - until it isn’t. In an initramfs, a chroot, or a stripped-down container, the usual helpers (findmnt, lsblk, blkid) just vanish.

mntui keeps working anyway. It’s both a recovery tool and a way to learn how Linux actually tracks mounts - through /proc, /sys, and the VFS namespace logic that glues it all together.

If nothing else, it’s a great excuse to poke around /proc/self/mountinfo and realize just how many layers there are between “mount this drive” and “why won’t this boot”.

The Guiding Rules

No magic daemons, no D-Bus, no guessing.

The Shape of It

+---------------------------+
|   (Optional TUI Frontend) |
|  ncurses / Textual client |
|  consumes JSON output     |
+---------------------------+
|        mntui-core (C)     |
|---------------------------|
| mountinfo.c   - /proc     |
| sysfs.c       - /sys      |
| fstab.c       - /etc      |
| actions.c     - syscalls  |
| json.c        - encoder   |
| main.c        - CLI/TUI   |
+---------------------------+
|     Linux Kernel APIs     |
| mount(2), umount2(2),     |
| statfs(), open(), etc.    |
+---------------------------+

The end goal is a static ELF around 200–400 KB. Tiny enough to drop in an initramfs or even embed into a Docker image.

Technical Aims

• Parse /proc/self/mountinfo directly and safely
• Spot mismatches between live mounts and /etc/fstab
• Perform atomic writes when updating fstab
• Call mount(2) and umount2(2) directly, no external tools
• Expose structured JSON for optional frontends or scripts

Basically: findmnt meets nmtui, but doesn’t explode when you forget to mount /usr.

Progress So Far

I’m still somewhere between discovery and architecture, but the core idea feels right: build one binary that always tells the truth about what’s actually mounted.

Why It Feels Right

Because when a system’s half-alive, it’s comforting to have one command that doesn’t lie. That’s the whole philosophy in a single line:

When nothing else runs, mntui should still tell the truth about your filesystems.

If You Want to Dig Deeper

If you want to go down the same rabbit hole:

• man 5 proc → the /proc/self/mountinfo spec
• man 2 mount → what all those MS_* flags mean
• I guess that there are other sources, but maybe you search for things now, or maybe you don’t, or maybe you don’t care, or maybe you don’t care about caring - That’s so cool how you don’t care… wow, that’s amazing! That’s incredible!

What were we talking about? I am tired now.
K thx! Bye!