Accessing ext4 partition with writable access without fstab entry

rng · 07-31-2013, 10:55 PM

I have Slackware14 full install (KDE), updated and otherwise working well. I recently tried to access an "ext4" formatted data partition by clicking on it in the left side partition list of Dolphin file manager. Dolphin asked me for password and then opened the partition. However, the partition is opening in read-only mode and I cannot create or edit any files there. How can I solve this problem without adding any entry to fstab (i.e. how to configure so that it mounts with writable access if clicked in file manager)? Thanks for your help.

willysr · 08-01-2013, 02:05 AM

can you post your /etc/fstab ?

rng · 08-01-2013, 02:57 AM

Quote:

can you post your /etc/fstab ?

Here it is:

Code:

/dev/sda3        /                ext4        defaults         1   1
#/dev/cdrom      /mnt/cdrom       auto        noauto,owner,ro,comment=x-gvfs-show 0   0
/dev/fd0         /mnt/floppy      auto        noauto,owner     0   0
devpts           /dev/pts         devpts      gid=5,mode=620   0   0
proc             /proc            proc        defaults         0   0
tmpfs            /dev/shm         tmpfs       defaults         0   0

As I mentioned above, I want to change auto-mount settings without making any change to fstab file.

willysr · 08-01-2013, 05:16 AM

what partition do you want to access? your fstab only list root partition

rng · 08-01-2013, 05:31 AM

Quote:

Originally Posted by willysr

what partition do you want to access? your fstab only list root partition

I have clarified in my earlier posts that I am mounting the partition by clicking on it in the file manager Dolphin when I need to access it. I do not want to make any fstab entry since the slackware14 installation is on an external disk which I may move to another computer with different hard disk structure.

Mark Pettit · 08-01-2013, 05:52 AM

I would add to fstab this line :

/dev/sdb1 /mnt/myusbdisk ext4 defaults,noauto,user 0 0

noauto says don't mount at boot
user says a user can mount it

You might need some other options, but that looks the basis to it.

rng · 08-01-2013, 08:59 AM

Is there any way I can solve this without any fstab entry?

saulgoode · 08-01-2013, 09:15 AM

I believe you can do that by editing the 'filesystem-mount-system-internal' section of /usr/share/polkit-1/actions/org.freedesktop.udisks.policy.

rng · 08-01-2013, 12:24 PM

Following parts of file /usr/share/polkit-1/actions/org.freedesktop.udisks.policy deal with 'mount':

Code:

<action id="org.freedesktop.udisks.filesystem-mount">
    <description>Mount a device</description>
    <description xml:lang="da">Montér en enhed</description>
    <message>Authentication is required to mount the device</message>
    <message xml:lang="da">Autorisering er påkrævet for at montere et fil system</message>
    <defaults>
      <allow_any>no</allow_any>
      <allow_inactive>no</allow_inactive>
      <allow_active>yes</allow_active>
    </defaults>
  </action>

<action id="org.freedesktop.udisks.filesystem-mount-system-internal">
    <description>Mount a system-internal device</description>
    <description xml:lang="da">Montér en intern enhed</description>
    <message>Authentication is required to mount the device</message>
    <message xml:lang="da">Autorisering er påkrævet for at montere et fil system</message>
    <defaults>
      <allow_any>no</allow_any>
      <allow_inactive>no</allow_inactive>
      <allow_active>auth_admin_keep</allow_active>
    </defaults>
  </action>

In the filesystem-mount-system-internal part, should I change both 'no' to 'yes'?

Mark Pettit · 08-01-2013, 03:04 PM

When I look at the hack required to make a disk mountable by a user and I see all that XML junk, somehow I feel Linux lost the plot. I'd still go with the fstab method as it's far simpler and will survive an upgrade. When you upgrade to the next version of Slack are you going to remember this obscure method and ridiculous file path and name?

guanx · 08-01-2013, 08:05 PM

I have a dirty solution: Open the GTK open file dialog, choose the unmounted filesystem from the left, then it's mounted read-write.

While this might be welcome by the OP, I am thoroughly horrified by how simple it is for an unprivileged user to do arbitrary mounts.

rng · 08-01-2013, 10:37 PM

I copied /usr/share/polkit-1/actions/org.freedesktop.udisks.policy and udisks2.policy files from another installed distribution (where mounting was as needed) and it worked well. I know this is not the best solution but it works.