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Mounting Volumes as a Block Device on Controller

Normally you would use $> 3t vol manage to do any work on a volumes filesystem or $> 3t vol fscheck to run a fsck however there are times were you need to access the filesystem directly as a block device to run these commands directly o perform other tasks.

Make sure the application is stopped and the volume you want to access is in an available state.

The vol manage and vol fscheck commands should be used whenever possible.

For 2.9.9 and earlier versions:

• For 2.9.9 and below grids volumes did not support partitions inside them so its failry straight forward.
• To mount the volume: $> 3tctl mount sv <appname>.class.<volname> Note: user volumes will be in the form of <appname>.user.<volname>
• This will mount the volume as a md block device which you can then mount as normal with: $> mount /dev/mdX /mnt/temp
• To unmount, first unmount the mdX device: $> umount /mnt/temp
• Now unmount the volume: $> 3tctl umount sv <appname>.class.<volname>
  • Example:
  • [root@ops ~]# 3tctl mount sv testvds1.class.VDS_CENTOS54.boot
    mount_id = /dev/md3
  • [root@ops ~]# mount /dev/md3 /mnt/temp
  • [root@ops ~]# ls /mnt/temp
    appliance boot etc lib
  • [root@ops ~]# umount /mnt/temp
  • [root@ops ~]# 3tctl umount sv testvds1.class.VDS_CENTOS54.boot

For 3.0+:

• In version 3.0 and up the volumes now support partitions inside of them so there is a extra step. Note: Not all volumes will have a internal partition scheme.
• To mount the volume as a block device you perform the same 3tctl command as above.

To mount the md device to the system you will need to find the offset first with sfdisk: $> sfdisk -uB -l /dev/mdX

• Example output:
• [root@SupportGrid ~]# sfdisk -uB -l /dev/md1
  Disk /dev/md1: 67328 cylinders, 2 heads, 4 sectors/track
  Warning: The partition table looks like it was made
  for C/H/S=*/39/5 (instead of 67328/2/4).
  For this listing I'll assume that geometry.
  Units = blocks of 1024 bytes, counting from 0
  Device Boot Start End #blocks Id System
  /dev/md1p1 32 266271 266240 83 Linux
  start: (c,h,s) expected (0,12,5) found (0,1,2)
  end: (c,h,s) expected (1023,38,5) found (33,38,5)
  /dev/md1p2 0 - 0 0 Empty
  /dev/md1p3 0 - 0 0 Empty
  /dev/md1p4 0 - 0 0 Empty
• The offset in this example is at block 32 and the Units is in 1024 bytes per block.
• The mount command only takes the value in bytes so we multiple 32x1024=32768

• To mount the volume you will specify the offset as an option to mount: $> mount -o offset=32768 /dev/md1 /mnt/temp
• The unmount commands are the same as the 2.9 and below grids. See above.