mount ramfs as user

Question

My fstab entry:

none    /home/jreinhart/ramdisk    ramfs    defaults,user   0 0

The directory before mounting:

drwxrwxr-x  2 jreinhart jreinhart  4096  Oct 17 11:31 ramdisk

The directory after mount ramdisk:

drwxr-xr-x  2 root     jreinhart  4096  Oct 17 11:31 ramdisk

So, you can see the problem. Once I mount, the owner changes to root, and the group permissions go to r-x so I cannot use this ramdisk. What gives?

I'm trying to do this without having to su.

Solution 1

I had the same problem. Using mode=777 instead of umask=777 as an option seems to work (Ubuntu 15.10).

Solution 2

Assuming this is Linux, you could also use tmpfs (see here for differences, i.e., why it might be advisable to use tmpfs), which is explained here and (see link) supports the options mode, gid and uid. There's the following paragraph in tmpfs.txt which might also be relevant:

These options do not have any effect on remount. You can change these
parameters with chmod(1), chown(1) and chgrp(1) on a mounted filesystem.

So maybe a sudo chown ... is still needed (I guess not, but I'm not quite sure about this, sorry.)

Comments

[Jonathon Reinhart]

I should have mentioned it, but I can't use tmpfs. tmpfs can be paged out to disk, which I need to avoid.

[Bryan Hunt]

Incorrect, ramfs has a max size option

[redanimalwar]

@BryanHunt source? Because I read this everywhere. "A ramfs derivative called tmpfs was created to add size limits"

[DepressedDaniel]

Except that it's not "once and for all" as the ramfs contents are lost when it is unmounted. OP probably wants the permissions to persist across reboots, which is why he is giving us an fstab entry to look at.

[Neurotransmitter]

This is the sole right answer. So the OP's fstab entry may look like this: none /home/jreinhart/ramdisk ramfs user,noauto,size=1024M,mode=0770 0 0. I removed defaults since it somewhat contradicts to user (it implies plenty of other options) and tuned mode to a more safe world-non-readable 0770 mask (so only root and jreinhart may read and write to this).