Mounting a Flash Filesystem

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TODO: {{#todo: Complete (11.27.13-12:15->KY+);(12.04.13-23:00->MD+);(12.20.13-11:00->MW+)|Klint Youngmeyer|oe 4,oe 5,ky,Complete,md,mw}}

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.

  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

    The highlighted line shows that the root device node for the flash device is sda containing one partition sda1.

Determine Which Partition to Mount

For this example, there is only one partition. It is possible that the flash device contains up to 4 primary partitions. If there are multiple partitions, choose the partition that contains the data that needs to be accessed. Repeat the steps below to mount the additional partitions if necessary. A partition with the number 5 (sda5) indicates an extended partition.

Determine Where to Mount the Device

Now that we know what partition we are going to mount, we need to determine where to mount it. The /mnt directory is typically used for the root mount point.

Create a directory to use for the mountpoint:

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

Any directory on the filesystem can be used as a mount point provided that the required permissions are obtained. If the directory used as the mount point contains files, they will be hidden when the flash device is mounted.

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, the flash device can be mounted 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

The device should be 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 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. Make sure there are no terminal windows open accessing any files or directories on the mounted filesystem before unmounting.

Continuing on with the example above, the device 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