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Author: fsmithred
To: dng
Subject: Re: [DNG] For all you automounter programmers
On 04/26/2016 03:36 PM, Hendrik Boom wrote:
> On Tue, Apr 26, 2016 at 02:08:33PM -0400, Steve Litt wrote:
>> Hi all,
>> It seems like everyone in the Devuan community has written his or her
>> own usb drive automounter, and I've just discovered something that will
>> help us all.
>> The thumb drive you buy at the store is formatted with a Windows file
>> system, and that's a good thing because it's mountable pretty much by
>> any device or computer. Sneakernet at its best.
>> But you must be root to mount it unless it's declared in /etc/fstab,
>> which is a bad idea for a number of reasons. And if you mount it as
>> root, normally the owner is root, and with its (typical) 755
>> permissions, a normal user can't write to it. Defeating its whole
>> purpose.
>> What you really want is for anyone in a certain group to be able to
>> write to it. I used group "floppy", because a USB drive is a pretty
>> good analog to a floppy, and floppies aren't even used much anymore. So
>> do the mount like this:
>> mount -o gid=floppy,fmask=113,dmask=002 /dev/sdd1 /mnt/thumb
>> or
>> mount -o gid=floppy,fmask=113,dmask=002 /dev/sdd1 /mnt/sdd1
>> The gid= means the thumb drive and all its files are group "floppy",
>> and the fmask and dmask make directories 775 and 664 respectively, so
>> group "floppy" can write.
>> I haven't yet tried this on a genuine ext4 formatted thumb drive, so I
>> don't know whether it would have any downside there. If so, the
>> different mount options would only appear if the thumb drive was
>> determined to be vfat/fat/msdos etc.
> I have a USB backup drive. I have root mount it, It's formatted
> ext3, and I have no problems doing so. It even allows me to use my
> systems's user IDs, though I expect it'll get confused if I were to use
> it on several systems with different UIDs.
> I just mount it as mount /dev/sdb1 /usbackup
> -- hendrik

This did not work for me:

$ mount -o gid=floppy,fmask=113,dmask=002 /dev/sdd1 /mnt/thumb
mount: only root can use "--options" option

First partition is vfat, second is ext4, and that won't mount, either. I'm
in the floppy group and also in plugdev group, and /mnt/thumb exists. What
am I doing wrong? Or is this something the user used to be able to do but
no longer can? (similar to what happened with blkid.)

I like pmount for mounting usb devices. It's pretty smart. For removable
devices, you don't need to list them in /etc/pmount.allow, and it handles
encrypted filesystems (cryptsetup/luks).