Can fstab options uid and gid be the user-group name or must they be numeric?

Question

I'm learning how to set up a tmpfs in fstab for my www-data user and I was wondering if I can use the actual user/group name instead if the numeric ids (personal preference)?

I'm on Debian with ext4, formatted with "msdos" during setup.

It seems to be working, but I'm wondering if this is a Debian-specific feature or will it work across platforms (I like portability)?

Here's what I've got:

$ vim /etc/fstab

# PHP temporary files.
tmpfs /tmpfs/php-session tmpfs defaults,size=512M,mode=1700,uid=www-data,gid=www-data,noexec,nodev,nosuid 0 0
tmpfs /tmpfs/php-upload  tmpfs defaults,size=256M,mode=1700,uid=www-data,gid=www-data,noexec,nodev,nosuid 0 0

Answer 1

The Linux mount program interprets non-numeric parameters to uid and gid options as user and group names respectively. This applies to all filesystem types. It works both if the options come from the command line and if they come from /etc/fstab.

Source: source (old (parse_opt), new (mnt_optstr_fix_gid, mnt_optstr_fix_uid)).

Answer 2

If you are using an ext filesystem, the uid and gid options are ignored, as the permissions used are set by the filesystem.

To quote gilles from another answer:

On an ext4 filesystem (like ext2, ext3, and most other unix-originating filesystems), the effective file permissions don't depend on who mounted the filesystem or on mount options, only on the metadata stored within the filesystem.

One method to resolve this would be to chown or chgrp the filesystem at some point when mounted.