Re: [gentoo-user] udisks and exfat

[Bill Kenworthy]

On 1/5/19 4:35 pm, Mick wrote:
> On Wednesday, 1 May 2019 03:32:21 BST Bill Kenworthy wrote:
>> Got sidetracked - turns out fuse and exfat on usb do not play well with
>> mounts as a user due to changes late last year.  It can now only be
>> mounted/unmounted by root.
>>
>> The second part (also due to fuse) is that to stop fuse (silently as ls
>> still showed the execute bit set) from interfering with execution of
>> files on the mounted device) it must be mounted as the user under a user
>> owned directory such as /home/user (mount cannot deal with this - it did
>> in the past, but something has changed).  So the solution is to mount
>> via root as the user you want (via sudo) under a mount point in the
>> users home.  This may all be unique to fuse-exfat, and which versions of
>> everything involved as I saw one email on the mechanics of the changes
>> saying fat is handled a little differently due to a different use
>> scenario.  And ext2/3/4 etc don't have the problem at all.  Auto-mount
>> on device plugin still doesn't happen so thats next on my list.
>>
>> /etc/fstab:
>>
>> /dev/sda1               /home/myuser/mnt           auto
>> rw,auto,exec,uid=1000,gid=1000,users,user=myuser                   0 0
>>
>>
>> BillK
> exFAT and VFAT are mounted with different permissions by udisks, without
> overriding options in fstab or command line.
>
> A random file in exFAT:
>
> $ stat /run/media/michael/VERBATIM32G/blah
>   File: /run/media/michael/VERBATIM32G/blah
>   Size: 32768     	Blocks: 64         IO Block: 4096   regular file
> Device: 811h/2065d	Inode: 19          Links: 1
> Access: (0777/-rwxrwxrwx)  Uid: ( 1000/ michael)   Gid: ( 1002/ michael)
> Access: 2018-06-08 11:20:50.000000000 +0100
> Modify: 2015-08-24 12:50:56.000000000 +0100
> Change: 2015-08-24 12:50:56.000000000 +0100
>  Birth: -
>
> A random file in FAT:
>
> $ stat /run/media/michael/CRUCIAL-8G/blah
>   File: /run/media/michael/CRUCIAL-8G/blah
>   Size: 1731366   	Blocks: 3384       IO Block: 4096   regular file
> Device: 810h/2064d	Inode: 124         Links: 1
> Access: (0644/-rw-r--r--)  Uid: ( 1000/ michael)   Gid: ( 1002/ michael)
> Access: 2019-04-08 01:00:00.000000000 +0100
> Modify: 2007-08-25 22:46:42.000000000 +0100
> Change: 2019-04-08 14:04:54.000000000 +0100
>  Birth: -
>
> Ditto for directories.
>
> exFAT:
>
> $ stat /run/media/michael/VERBATIM32G/Foo
>   File: /run/media/michael/VERBATIM32G/Foo
>   Size: 32768     	Blocks: 64         IO Block: 4096   directory
> Device: 811h/2065d	Inode: 24          Links: 1
> Access: (0777/drwxrwxrwx)  Uid: ( 1000/ michael)   Gid: ( 1002/ michael)
> Access: 2018-02-11 17:22:52.000000000 +0000
> Modify: 2018-02-11 17:22:54.000000000 +0000
> Change: 2018-02-11 17:22:54.000000000 +0000
>  Birth: -
>
>
> FAT:
>
> $ stat /run/media/michael/CRUCIAL-8G/Foo
>   File: /run/media/michael/CRUCIAL-8G/Foo
>   Size: 4096      	Blocks: 8          IO Block: 4096   directory
> Device: 810h/2064d	Inode: 79          Links: 2
> Access: (0755/drwxr-xr-x)  Uid: ( 1000/ michael)   Gid: ( 1002/ michael)
> Access: 2019-04-08 01:00:00.000000000 +0100
> Modify: 2019-04-08 14:43:26.000000000 +0100
> Change: 2019-04-08 14:43:26.000000000 +0100
>  Birth: -
>
> The mount options are different as shown below.
>
> exFAT:
>
> $ findmnt -oOPTIONS /dev/sdb1
> OPTIONS
> rw,nosuid,nodev,relatime,user_id=0,group_id=0,default_permissions,allow_other,
> blksize=4096
>
> FAT:
>
> $ findmnt -oOPTIONS /dev/sdb
> OPTIONS
> rw,nosuid,nodev,relatime,uid=1000,gid=1002,fmask=0022,dmask=0022,codepage=437,
> iocharset=iso8859-1,shortname=mixed,showexec,utf8,flush,errors=remount-ro
>
>
> In the above examples I used udisksctl to mount the devices.  I understand
> Gnome expose via Gvfs an API to handle I/O to block devices, which desktop
> applications can plug into without performing raw kernel calls to hardware
> devices (like e.g. /bin/mount does).  I don't run Gnome and am not familiar
> with its internals to know how similar it is with udisksctl.
>
> Regarding mounting with udisksctl I don't know why exFAT and VFAT are
> different, but the udisksctl man page provides this revealing information on
> the mount permissions allowed:
>
>       The device will be mounted with a safe set of default options. You
>       can influence the options passed to the mount(8) command with
>       --options. Note that only safe options are allowed - requests with
>       inherently unsafe options such as suid or dev that would allow the
>       caller to gain additional privileges, are rejected.
>
> HTH.

Sounds like you are using gnome/systemd ... thats a whole other box of
worms to open.  This is a gnomeless openrc system with a recently
getting elogind to replace consolekit.


BillK