Mounting a Flash Filesystem

TODO: {{#todo: SEOKWREV (11.27.13-12:15->KY+);(12.04.13-23:00->MD+);(12.20.13-11:00->MW+);(03.06.14-14:55->BS-);(04.11.14-10:05->BS+)|Klint Youngmeyer|oe 4,oe 5,ky,SEOKWREV,md,mw,bs}}

In order to use a flash filesystem on an EMAC OE system, it must be mounted first.

There are four steps to mounting a flash filesystem on an EMAC OE machine:

1. Determine which device node is assigned to the flash device.

2. Determine which partition to mount.

3. Determine where to mount the device.

4. Mount the device.

Determining the Device Node Assigned to the Flash Device

The easiest way to determine which device node is assigned to a particular flash device is to inspect the output of the dmesg command shortly after the device has been connected to your machine. Follow these steps to do so:

1. Insert the SD, CF or microSD card or plug in the USB flash device to your EMAC OE machine.

2. Wait a few seconds for the device to settle and be recognized by the OS.

3. Run this command at a shell on your EMAC OE machine:
   

   root@emac-oe:~# dmesg | tail -n 15
   

4. Inspect the output. The output should look similar to the following:

   usb 2-2: new full speed USB device using at91_ohci and address 2
   usb 2-2: not running at top speed; connect to a high speed hub
   usb 2-2: configuration #1 chosen from 1 choice
   scsi0 : SCSI emulation for USB Mass Storage devices
   usb-storage: device found at 2
   usb-storage: waiting for device to settle before scanning
   scsi 0:0:0:0: Direct-Access              Patriot Memory   PMAP PQ: 0 ANSI: 4
   usb-storage: device scan complete
   sd 0:0:0:0: [sda] 15634432 512-byte hardware sectors: (8.00 GB/7.45 GiB)
   sd 0:0:0:0: [sda] Write Protect is off
   sd 0:0:0:0: [sda] Mode Sense: 23 00 00 00
   sd 0:0:0:0: [sda] Assuming drive cache: write through
   sd 0:0:0:0: [sda] Assuming drive cache: write through 
   sda: sda1
   sd 0:0:0:0: [sda] Attached SCSI removable disk
   

   Inside square brackets, we see sda. This is the root device node assigned to our flash device.

Determine Which Partition to Mount

On a line by itself, we see:

sda: sda1

This means one partition was found on our device: sda1. This is the partition we will use.

Determine Where to Mount the Device

Now that we know what device node we are going to mount, we need to determine where to mount it. The /mnt directory is typically used for this (mnt is short for mount).

Create a directory to use for the mountpoint:

root@emac-oe:~# mkdir /mnt/myflash

Alternatively, you can pick another place in the filesystem to use. Just make sure you have permission to create a directory in that location. If the directory contains files, it will still be used as the mountpoint when the mount command is issued; however, the files contained in the directory will be hidden for as long as the directory is in use as a mountpoint. This could create a great deal of confusion, so beware this potential pitfall.

Mount the Device

Now that sda1 has been determined to be the partition to mount and /mnt/myflash has been created to be used as the mountpoint, we can mount our flash device with the following command:

root@emac-oe:~# mount /dev/sda1 /mnt/myflash

If no message is returned from the above command, then it succeeded. To verify this, try the following command

root@emac-oe:~# mount | grep sda1

You should see your device listed in the output of the above command. If it is listed more than once, it may have been mounted automatically by the OS. If so, inspection of the output should show you where it was mounted.

Unmounting the Filesystem After Use

After you are finished using the flash device, you may wish to unmount it (similar to "Safely Removing" a device on other operating systems). The umount command is used for this purpose.

Continuing on with the example above, the device mounted above would be unmounted with the following command:

root@emac-oe:~# umount /mnt/myflash

If it was automounted elsewhere, it will also need to be unmounted from that mountpoint before it will be safe to remove the device. For instance, if the automounter mounted it on /media/sda1, then issue the following command:

root@emac-oe:~# umount /media/sda1