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  • Resizing NMIS VMs
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If it should become necessary to expand the storage space for /data, the following set of instructions should help you to perform that change with minimal NMIS downtime.

The resizing procedure is quite simple, for size increases at least. The two required steps are:

  • adding extra storage 'hardware' to the VM
  • informing the operating system of the extra storage, attaching the storage and resizing the active file systems.

This is possible because the Opmantek Virtual appliance makes use of Linux's excellent LVM support (Logical Volume Management, described in more details here).

First Step, determine the current state

login as as root to the VM and run


which will show you something like this

/dev/sdb   vg_nmis64_data  lvm2 a-   100.00g    0

meaning 100gb are allocated and vg_nmis64_data is using it. Note that on some older VMs the volume group is called vg_data instead; the resizing process can be performed as long as you remember to change the volume group name in the command invocations.

Next run


and it'll tell you

lv_data vg_nmis64_data -wi-ao 100.00g

that the lv_data logical volume is using all of vg_nmis64_data's space, and a final

df -h

will tell you that

 /dev/mapper/vg_nmis64_data-lv_data 99G 39G 56G 42% /data

 /data is the filesystem on top of the logical volume, which has a size of 99GB (plus spare change), of which 39BG are used. It is recommended that you rerun these commands at the end to verify that the resizing has worked.

Second Step,  Resize Storage Hardware

At this point it'll be simplest to open your vmware client, resize the VM's disk 2 to the desired new size and then reboot the VM to make it pick up the size change.

If you would like to avoid any downtime and not reboot, that's also possible if your virtualisation system allows adding or resizing disks "on the go": Virtualbox doesn't allow that, Vmware does. Please note that Vmware doesn't let you resize disks if there are any snapshots present; if that is the case, then these snapshots must be removed before the resize can occur.

In many cases it will be simpler to add another 'disk' to the system rather than resizing either of the existing 'disks'.

Third Step, Informing the OS and resizing the file system

When the VM boots the newly resized disk 2 (aka /dev/sdb) will be detected but volume group and logical volume still need to be told about the change of 'hardware'.

If you added a new disk

If you did add disks instead of resizing existing ones, the OS should have picked them up dynamically and they should show up as /dev/sdc, sdd etc. In this case they must be registered as physical volumes (optionally after partitioning), and added to the volume group.

To do so, login as root first. Then check under what id your new disk has shown up, and add it as a whole as a new physical volume:

cat /proc/scsi/scsi
Host: scsi2 Channel: 00 Id: 01 Lun:  # the '2' indicates /dev/sdc is the device file
# this marks the whole disk as physical volume
pvcreate /dev/sdc 
# this addds the pv to the volume group
vgextend vg_nmis64_data /dev/sdc
If you resized an existing disk that was partitioned (e.g. the FIRST harddisk):

The resized disk will have grown, but the partition table on it won't reflect the new size yet, and thus  the extra space needs claiming before it can be accessed.

To do that, login as root, then add a new partition to the existing disk, make it use all the new space and give it type 8E (= Linux LVM), reboot to ensure the partition table is actually reread (this doesn't always work on-the-go); when that is done, create a new physical volume on that extra partition.

# assuming the modified disk is the first one, ie. /dev/sda
cfdisk /dev/sda # but you may prefer to use fdisk or gdisk instead
#...go through dialog to claim the extra space, let's assume we create /dev/sda4
pvcreate /dev/sda4
If you resized an existing disk that was used without partitions, just as phyiscal LVM volume (e.g. 2nd or 3rd harddisk):

In this case we just tell the LVM subsystem that there's now more space available in a particular physical volume. Login as root, then run

# assuming that the second disk was resized
pvresize /dev/sdb

which will tell you that sdb is now as large as the disk2 size you configured in your virtualisation tool.

New or resized disk

Finally we're ready to add the new space to the logical volume we need it in; To do that, login as root and run

lvextend -l 100%VG /dev/vg_nmis64_data/lv_data

to perform the resizing for the logical volume, follwed by

resize2fs /dev/vg_nmis64_data/lv_data

which will take a bit of time and eventuallly tell you that  it has resized the file system for the new extended disk size. A final

df -h

should show that /data is now larger than before.



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