Mounting permissions for simple user

Panagiotis_IOA · 03-15-2006, 04:17 PM

When I'm trying to mount CD-ROM or USB flash-disk I got the message that only root has these permissions. I tried by changing permission at the files: /dev/cdrom and /dev/sda1 (for the flash-disk) but again it didn't work.
Also, I have a FAT32 partition and I can read and write as root but as user I can only read. I tried and here to change the permissions but they don't unfortunately they didn't.

Bruce Hill · 03-15-2006, 06:00 PM

This is what you need in your /etc/fstab to mount the flash disk read/write as a normal user:

Code:

/dev/sdc1        /mnt/usb         vfat        noauto,user,rw,umask=1000  0  0

Change the device (/dev/sdc1) and mount point (/mnt/usb) and filesystem (vfat) appropriately.

This is what you need to mount your CD-ROM as a normal user (can't mount read/write):

Code:

/dev/hdc         /mnt/cdrw        iso9660     noauto,user,ro   0   0

Change the device (/dev/hdc) and mount point (/mnt/cdrw) appropriately.

This is what you need in your /etc/fstab to mount the FAT32 partition read/write as a normal user:

Code:

/dev/sda2        /Shared          vfat        user,umask=1000,rw,auto  1   0

Change the device (/dev/sda2) and mount point (/Shared) appropriately.

You can make the changes to /etc/fstab as root, then issue "umount /<yourFAT32mount" and then issue "mount /<yourFAT32mount" and it will be mounted read/write. No need to reboot your box.

Neither CD-ROM, CD-RW, DVD-ROM, nor DVD+/-RW can be mounted read/write (rw) because they are all read-only filesystems. You use software to write to medium in these devices such as growisofs, dvd+rw-tools, dvdrtools, and cdrecord. There are also GUI frontends such as K3B which use those command line tools.

For the flash disk, you'll need to know where your system is attaching it. Plug that thing in and wait a few seconds (5 to 30 depending upon your system) then issue and read:

Code:

bruce@silas:~$ dmesg | tail
usb 1-6: reset high speed USB device using ehci_hcd and address 7
usb 1-6: reset high speed USB device using ehci_hcd and address 7
usb 1-6: reset high speed USB device using ehci_hcd and address 7
sdc: Write Protect is off
sdc: Mode Sense: 02 00 00 00
sdc: assuming drive cache: write through
 sdc: sdc1
sd 4:0:0:0: Attached scsi removable disk sdc
sd 4:0:0:0: Attached scsi generic sg2 type 0
usb-storage: device scan complete

That's why I have /dev/sdc1 to mount at /mnt/usb then /dev/sdd1 to mount at /mnt/usb1 just in case I need to use both my flash disks at one time. Notice that I haven't yet mounted the disk, but because of my fstab entry above:

Code:

bruce@silas:~$ mount /mnt/usb && ls -alhn /mnt/usb
total 147M
drwxrwxrwx 2 1001 100 2.0K 1970-01-01 07:00 ./
drwxr-xr-x 8    0   0  192 2006-03-11 17:24 ../
-rwxrwxrwx 1 1001 100  20M 2006-03-13 12:44 AdbeRdr705_enu_full.exe*
-rwxrwxrwx 1 1001 100 5.0M 2006-02-08 17:12 Firefox\ Setup\ 1.5.0.1.exe*
-rwxrwxrwx 1 1001 100  91M 2006-03-13 12:42 OOo_2.0.1_Win32Intel_install_wJRE.exe*
-rwxrwxrwx 1 1001 100 6.1M 2006-03-13 12:41 Thunderbird\ Setup\ 1.5.exe*
-rwxrwxrwx 1 1001 100 4.3M 2006-03-13 02:29 epson10511.exe*
-rwxrwxrwx 1 1001 100 2.0M 2006-03-13 02:39 epson10576.exe*
-rwxrwxrwx 1 1001 100 1.4M 2006-03-13 02:34 epson11667.exe*
-rwxrwxrwx 1 1001 100 6.7M 2006-03-13 12:43 gaim-1.5.0.exe*
-rwxrwxrwx 1 1001 100   65 2006-03-13 13:41 key*
-rwxrwxrwx 1 1001 100 8.5M 2006-03-13 12:41 nentenst.exe*
-rwxrwxrwx 1 1001 100 184K 2006-02-01 03:00 slack1.png*
-rwxrwxrwx 1 1001 100 1.6M 2006-03-13 12:43 xchat-2.6.1a.exe*

I issue two commands at once using "&&" to save time. And then after you're finished with him:

Code:

bruce@silas:~$ umount /mnt/usb

and you can safely unplug him from your system.

Panagiotis_IOA · 03-15-2006, 06:36 PM

Thanks a lot for your reply and the information you gave me. Now, and the three of them are working properly.
After reading your post and you mention about two flashdisks it came to my mind what would I do if I get another one.
I mount the one I have at /dev/sda1 and under the link /mnt/memstick. If I plug a second one will it like /dev/sda2 ?

chrisortiz · 03-15-2006, 06:40 PM

Quote:

I mount the one I have at /dev/sda1 and under the link /mnt/memstick. If I plug a second one will it like /dev/sda2 ?

it would be /dev/sbd1
a third drive would be /dev/sbc1
the numbers refer the the partitions on the device and letters refer to the devices

Bruce Hill · 03-15-2006, 06:42 PM

If you plug in two at the same time it will take the next device. You can make more mount points. Issue "dmesg | tail" to determine which device the kernel gave it. You can also use udev (man udev) to mount devices according to their names you setup in udev rules. However, udev seems to be messy, and this 2.6.x.y kernel is a moving target; so I don't use udev. Perhaps some really smart Slacker will come along and prove me wrong. I'd sure like to just plug devices in and they're there and They Just Work (TM) like in those other, so poorly coded OSes (Mac and Windows).

Panagiotis_IOA · 03-15-2006, 06:44 PM

Ok, thanks a lot! I'll try with a second flashdisk soone or later

Bruce Hill · 03-15-2006, 06:45 PM

Quote:

Originally Posted by chrisortiz

it would be /dev/sbd1
a third drive would be /dev/sbc1
the numbers refer the the partitions on the device and letters refer to the devices

You're close, but incorrect.

It would be:
sda1
sdb1
sdc1
sdd1

It is s (scsi) d (device) a (first device) 1 (partition number).

You could have many partitions on one scsi (or scsi emulated) device.

chrisortiz · 03-15-2006, 06:50 PM

oh i had a typo =) thanks for catching it.