5

Out of curiosity, is this possible nowadays? I remember some old Slackware versions did support FAT root partition but I am not sure if this is possible with modern kernels and if there are any distros offering such an option. I am interested in pure DOS FAT (without long names support), VFAT 16/32 and exFAT.

PS: Don't tell me I shouldn't, I am not going to use this in production unless necessary :-)

Ivan
  • 17,368
  • 35
  • 93
  • 118
  • Signs point to "no" http://superuser.com/questions/782849/why-does-ubuntu-linux-insist-on-been-installed-on-a-ext-partition-and-can-it-be, but interesting Linux history question anyway. – dhag Dec 08 '15 at 19:24
  • 1
    *I am not going to use this in production unless necessary* Seriously? *unless necessary*? Man, you scare the heck out of me. ;) – Alois Mahdal Dec 08 '15 at 20:14
  • If it's possible it absolutely and definitely makes zero sense, like a safety net made in toilet paper. –  Dec 08 '15 at 22:16
  • Answer is "Technically, yes, but you'll run into a whole slew of issues. Solvable ones, and you'll come out with enhanced understanding of and appreciation for the POSIX filesystem, but it's not going to be a fun experience." – Shadur Dec 09 '15 at 09:32

2 Answers2

11

OK, I tried it.

First two problems from the beginning: NO support for hard and symbolic links. It means that I had to copy each file, duplicating it and wasting space.

Second problem: no special file support at all. This means things like /dev/console are unavailable at boot time to init before even /dev is remounted as tmpfs.

Third problem: you will loose permissions enforcing.

But out of this, there were no issues. My own system was booted successfully on a vfat volume.

QEMU LinFAT

Normally I would not do that, too.

0

It's not possible out of the box, because the umsdos driver which allows us to use Unix features on FAT drives were removed from Linux kernel 2.6

Umsdos is a linux file system. It provide an alternative to the EXT2 file-system. Its main goal is to achieve easier coexistence with Ms-DOS data by sharing the same partition. This document explain first how to use Umsdos in different configuration, and later explain its operation and try to provide some information letting you decide if it is a good choice for you (see UMSDOS-WHY-TO at the end).

https://tldp.org/HOWTO/UMSDOS-HOWTO.html

Without the ability to store permissions and symlinks lots of things will break, so no distro can offer that feature in their releases

umsdos

The key advantage to umsdos out of the three is that it provides full Unix file semantics. Therefore, it can be used in situations where it is desirable to install Linux on and run it from a FAT disk volume, which require such semantics to be available. However, Linux installed on and running from such a disk volume is slower than Linux installed on and running from a disk volume formatted with, for example, the ext2 filesystem format.[1][12] Further, unless a utility program is regularly run every time that one switches from running Windows to running Linux, certain changes made to files and directories on the disk by Windows will cause error messages about inaccessible files in Linux.

FAT filesystem and Linux

The modern replacement is POSIX Overlay Filesystem but since it's a FUSE driver, using it for rootfs would be tricky

A FUSE filesystem that provides POSIX functionality - UNIX-style permissions, ownership, special files - for filesystems that do not have such, e.g. vfat. It can be seen as a contemporary equivalent of the UMSDOS fs.

phuclv
  • 2,001
  • 1
  • 16
  • 41