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Re: User rw Permissions on New Hard Drive




On Thu 07 Mar 2019 at 13:49:42 (-0700), Cousin Stanley wrote:
> David Wright wrote:
> 
> > I prefer to populate fstab with canonical information 
> > that actually belongs to the filesystems that are to be mounted. 
> 
>   I don't understand what you're saying here.
> 
>   Does a disk label not belong to a filesystem
>   that is to be mounted ?

Yes. Using a concrete example from /etc/fstab, in:

LABEL=sand1g /media/camera1g vfat rw,errors=remount-ro,utf8,tz=UTC,shortname=lower,user,noauto,fmask=137,dmask=027

the characters sand1g have been written in the partition on the
device, an SD card. (The fact that they're lowercase means that
it's unlikely I wrote that LABEL in DOS or Windows.) But were
I to have put in /etc/fstab:

/dev/disk/by-label/sand1g /media/camera1g vfat rw,errors=remount-ro,utf8,tz=UTC,shortname=lower,user,noauto,fmask=137,dmask=027

I would not expect to find the characters /dev/disk/by-label/ anywhere
in the partition. That string belongs to the linux system, not to
the card. That's what I meant by "actually belongs to the filesystems".

> > A filesystem  that has a label, 
> > has that label regardless of any OS. 
> >
> > It's real, defined in the filesystem's documentation.
> >
> > All that stuff in /dev/disk/ is just an ephemeral 
> > bunch of convenient symbolic links, presumably conjured 
> > up by udev or somesuch, if not the linux kernel
> 
>   But are they not accurate after boot
>   for particular disks on a particular machine ?

I don't question its accuracy.

> > I'm not clear about which other sort of label
> > might be referenced by LABEL=
> 
>   I'm not either but if I use /dev/disk/by-label
>   I  think  I know what sort  that  is .... :)

OK, I thought you had something in mind.

BTW, in looking at   man mount   (to remind myself of the -L option),
I noticed that it actually mentions this business:

   "The recommended setup is to use tags (e.g. LABEL=label) rather
   than /dev/disk/by-{label,uuid,partuuid,partlabel} udev symlinks in
   the /etc/fstab file. Tags are more readable, robust and portable."

Cheers,
David.