[SOLVED] Write permissions to external drive

nix.noob · 02-06-2015, 01:47 PM

I have an external disk but I can only write to it using sudo, not as my normal user.

The commands I've issued are:

Code:

sudo mkdir /media/USBSSD
sudo mount -t auto /dev/sda1 /media/USBSSD
sudo chmod 777 /media/USBSSD
sudo mkdir /media/USBSSD/share

How can I set it up so that other users can write to it?

Keruskerfuerst · 02-06-2015, 01:57 PM

You should add a line t oyour /etc/fstab like this

/dev/sda1 auto /media/USBSSD users 0 2

nix.noob · 02-06-2015, 02:26 PM

Thank you for your suggestion.
It already said

Code:

/dev/sda1       /media/USBSSD   auto    noatime           0       0

So I changed it to

Code:

/dev/sda1       /media/USBSSD   auto    users           0       2

but it didnt seem to make any difference.

yancek · 02-06-2015, 02:48 PM

To give users rw to another partition, an example below which works for me on an ext4 filesystem. Is this an ntfs filesystem and you forgot to mention that?? Makes a difference. So what happened when you ran the mkdir command, you didn't post the output.

Quote:

/dev/sda1 /media/USBSSD ext4 auto,user,rw 1 2

nix.noob · 02-06-2015, 04:29 PM

Hi,
Its vfat.

Code:

$ mkdir /media/USBSSD/share
mkdir: cannot create directory `/media/USBSSD/share': Permission denied

$ sudo mkdir /media/USBSSD/share
no output from this, it worked
$ sudo chmod 777 /media/USBSSD
$ echo foo > /media/USBSSD/share/foo.txt
-bash: /media/USBSSD/share/foo.txt: Permission denied
$ ls -l /media/USBSSD/
total 16
drwxr-xr-x 2 root root 16384 Feb  6 22:19 share

sudo cfdisk:

Code:

Name    Flags   Part Type   FS Type  [Label]  Size (MB)
--------------------------------------------------------------
sda1   Boot    Primary     vfat                    30016.66    *

I tried

Code:

/dev/sda1 /media/USBSSD auto auto,user,rw 1 2

and

Code:

/dev/sda1 /media/USBSSD vfat auto,user,rw 1 2

but I still get

Code:

$ echo foo > /media/USBSSD/share/foo.txt
-bash: /media/USBSSD/share/foo.txt: Permission denied

(where foo.txt doesn't exist yet)

Habitual · 02-06-2015, 04:33 PM

https://help.ubuntu.com/community/Au...ountPartitions

nix.noob · 02-06-2015, 04:49 PM

That page (thanks for the link) suggests that for FAT partitions which are to be accessible by everyone, use the string user,auto,fmask=0111,dmask=0000 in fstab, so I changed mine to say

Code:

/dev/sda1       /media/USBSSD   vfat    user,auto,fmask=0111,dmask=0000      0       2

and tried writing the file again but still permission denied.
So then I tried adding the rw flag too but that didnt make a difference

Code:

/dev/sda1       /media/USBSSD   vfat    user,auto,fmask=0111,dmask=0000,rw      0       2

yancek · 02-06-2015, 06:45 PM

Which Ubuntu are you using? The more recent version have flash and external devices under /media/username
Post the permissions: ls -ld /media/USBSSD
What kind of data is on it?

nix.noob · 02-07-2015, 05:15 AM

I'm not running Ubuntu, I'm using the most up-to-date version of raspbian.
I'm trying to connect a new empty disk to a raspberry pi to act as a cheap nas.

Code:

$ ls -ld /media/USBSSD/
drwxr-xr-x 3 root root 16384 Jan  1  1970 /media/USBSSD/

There is no data on it as it's a new disk.

jpollard · 02-07-2015, 06:49 AM

Usually, that is done by giving the separate users a separate directory on the disk. That way they control who can read what within their directory.

You could also make the base directory sticky... (as in chmod ugo+rwxt the/media/USBSSD) which is the same as the access mode of /tmp. This allows any user to create a directory there, and then put stuff on it.

nix.noob · 02-07-2015, 07:07 AM

I tried

Code:

$ sudo chmod ugo+rwxt /media/USBSSD/
chmod: changing permissions of `/media/USBSSD/': Operation not permitted

In this case it's not a problem if users can edit each others files, so I'm not sure it needs to be sticky.
So I also tried without the sticky bit

Code:

$ sudo chmod ugo+rwx /media/USBSSD/

but I don't think it is altering the ability to write. I still can't create new files except with sudo

Code:

$ ls -ld /media/USBSSD/
drwxr-xr-x 3 root root 16384 Jan  1  1970 /media/USBSSD/
$ echo foo > /media/USBSSD/share/foo.txt
-bash: /media/USBSSD/share/foo.txt: Permission denied

michaelk · 02-07-2015, 07:50 AM

Since you are wanting to use the drive for a NAS it would make more sense to reformat (via mkfs) it with ext3 or other linux filesystem. A FAT32 (vfat) filesystem is not compatible with linux permissions.

And mount it as:

Quote:

/dev/sda1 /media/USBSSD ext3 defaults 0 2

yancek · 02-07-2015, 07:58 AM

My understanding has always been that Linux permissions aren't comatible with windows filesystem types. You indicate you can write to it as sudo and note the owner:group both root:root. Might also try changing one of those.

jpollard · 02-07-2015, 08:08 AM

You likely have to be root to change permissions on /media/USBSSD/

Now if it is automatically mounted at boot then the permissions will likely go away (it depends on the filesystem used for /media, which is usually tmpfs for automatic mounts - that way it is also cleaned up on reboots as /media has to be recreated on each boot).

jpollard · 02-07-2015, 08:10 AM

Quote:

Originally Posted by yancek

My understanding has always been that Linux permissions aren't comatible with windows filesystem types. You indicate you can write to it as sudo and note the owner:group both root:root. Might also try changing one of those.

That translation is what Samba is used for (as well as protocol compatibility).