OVH Guide

Repartitioning a VPS after an upgrade

Last updated 14th November, 2017

Objective

When you upgrade your VPS, you might need to repartition your storage space. Here are the steps to follow.

Repartitioning could permanently damage your data. OVH cannot be held responsible for any loss or damage to your data. Before doing anything, make sure you back up all of your data.

Requirements

  • You must have SSH access to the VPS (root access).
  • You need to reboot the server in rescue mode.

Instructions

Following an upgrade, the RAM and processor (CPU) will automatically be adjusted. This won’t systematically be the case for the storage space.

This guide explains the steps you need to follow to increase your storage space.

Back up your data

Attempting to extend a partition can lead to a loss of data. It is therefore strongly recommended that you back up the data on your VPS.

Unmount the partition

After logging in to your VPS in rescue mode, your partition will automatically be mounted. In order to resize it, you will need to unmount it. If you know the name of your partition, you can skip the following step. If you don’t know the name of your partition, use the following command:

lsblk

The partition corresponding to rescue mode will be the one mounted in the / directory, which is actually the system root. In contrast, the partition of your VPS will probably be placed in the directory associated with /mnt, or not mounted at all.

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 254:0 0 10G 0 disk
└─sda1 254:1 0 10G 0 part /
sdb 254:16 0 25G 0 disk
└─sdb1 254:17 0 25G 0 part /mnt/sdb1

To unmount your partition, use the following command:

unmount /dev/sdb1

Check the filesystem

After unmounting the partition, you should check the filesystem (filesystem check) to see if there are errors in the partition. The command is as follows:

e2fsck -yf /dev/sdb1

e2fsck 1.42.9 (4-Feb-2014)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/dev/sdb1: 37870/1310720 files (0.2% non-contiguous), 313949/5242462 blocks

If you receive a bad magic number in superblock error, do not proceed. A procedure to fix this issue is given at the end of this guide.

Launch the fdisk application

If the filesystem check is completed successfully, launch the fdisk application. In the settings, you need to enter the name of the disk and not the name of the partition. For instance, if your partition is sdb1 instead of vdb1, the disk name will be /dev/sdb.

fdisk -u /dev/sdb

This application has several sub-commands, which you can view with the command m.

Delete the old partition

Before deleting the old partition, it is recommended that you write down the number corresponding to the first sector of the partition. You can find this information through the command p. The information is listed under the Start field. Save this data for later.

Command (m for help): p

Disk /dev/sdb: 21.5 GB, 21474836480 bytes
54 heads, 49 sectors/track, 15851 cylinders, total 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000132ff

Device Boot Start End Blocks Id System
/dev/sdb1 * *2048* 41941745 20969849 83 Linux

If you haven’t backed up your data, this is the point of no return.

Then delete the partition with the command d.

Command (m for help): d
Selected partition 1

The single partition will automatically be deleted.

Create a new partition

You now need to create a new partition with the command n. It is recommended that you use the default values.

Command (m for help): n
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-41943039, default 2048): 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): 41943039.

On the First sector line, check that the default value is the same as the one you have previously written down. If it is different, use the value you have written down.

Making the partition bootable

You now need to ensure that the partition is bootable. You can do this using the command a.

Command (m for help): a

Partition number (1-4): 1

Save your changes and exit the application with the command w:

Command (m for help): w

The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

Extending the filesystem on the partition

The partition has been extended, but the filesystem still occupies the same space as before. To extend it, simply enter the following command:

resize2fs /dev/sdb1

resize2fs 1.42.9 (4-Feb-2014)
Resizing the filesystem on /dev/sdb1 to 5242624 (4k) blocks.
The filesystem on /dev/sdb1 is now 5242624 blocks long.

Check the results

In order to check if the extension has been successful, you can mount the newly created partition and verify its size.

mount /dev/sdb1 /mnt
df -h

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 991M 793M 132M 86% /
none 4.0K 0 4.0K 0% /sys/fs/cgroup
udev 1.9G 12K 1.9G 1% /dev
tmpfs 386M 360K 386M 1% /run
none 5.0M 0 5.0M 0% /run/lock
none 1.9G 0 1.9G 0% /run/shm
none 100M 0 100M 0% /run/user
/dev/sdb1 50G 842M 48G 2% /mnt

You will find the new partition size listed below the label size.

How do I fix a bad magic number in superblock error?

If the command e2fsck returns the error message bad magic number in superblock, you should check and repair the filesystem by using a backup of the superblock. To see which backups of the superblock are available, enter the following command:

dumpe2fs /dev/sdb1 | grep superblock

Primary superblock at 0, Group descriptors at 1-6
Backup superblock at 32768, Group descriptors at 32769-32774
Backup superblock at 98304, Group descriptors at 98305-98310
Backup superblock at 163840, Group descriptors at 163841-163846
Backup superblock at 229376, Group descriptors at 229377-229382
Backup superblock at 294912, Group descriptors at 294913-294918
Backup superblock at 819200, Group descriptors at 819201-819206
Backup superblock at 884736, Group descriptors at 884737-884742
Backup superblock at 1605632, Group descriptors at 1605633-1605638
Backup superblock at 2654208, Group descriptors at 2654209-2654214
Backup superblock at 4096000, Group descriptors at 4096001-4096006
Backup superblock at 7962624, Group descriptors at 7962625-7962630
Backup superblock at 11239424, Group descriptors at 11239425-11239430
Backup superblock at 20480000, Group descriptors at 20480001-20480006
Backup superblock at 23887872, Group descriptors at 23887873-23887878

Then use the first superblock backup to check and repair the filesystem:

fsck -b 32768 /dev/sdb1

Go further

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