Live resizing of an ext4 filesytem on linux

Recently I was working on a Linux VM which was running out of disk space and I wanted to increase the available space. I didn’t want to just add another drive and mount is separately but to to increase the size of the root partition.

Disclaimer: The following instructions can easily screw your data if you make a mistake. I was doing this on a VM which I backed up before performing the following actions. If you loose your data because you didn’t backup don’t come and complain.

The VM I was working on is a stock Ubuntu 12.10 Desktop install.

First: Increase the disk size.

In ESXi this is simple, just increase the size of the virtual disk. Now you have a bigger hard drive but you still need to a) increase the partition size and b) resize the filesystem.

Second: Increase the partition size.

You can use fdisk to change your partition table while running. The stock Ubuntu install has created 3 partitions: one primary (sda1), one extended (sda2) with a single logical partition (sda5) in it. The extended partition is simply used for swap, so I could easily move it without losing any data.

  1. Delete the primary partition
  2. Delete the extended partition
  3. Create a new primary partition starting at the same sector as the original one just with a bigger size (leave some for swap)
  4. Create a new extended partition with a logical partition in it to hold the swap space
me@ubuntu:~$ sudo fdisk /dev/sda

Command (m for help): p

Disk /dev/sda: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 cylinders, total 524288000 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: 0x000e49fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048   192940031    96468992   83  Linux
/dev/sda2       192942078   209713151     8385537    5  Extended
/dev/sda5       192942080   209713151     8385536   82  Linux swap / Solaris

Command (m for help): d
Partition number (1-5): 1

Command (m for help): d
Partition number (1-5): 2

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):
Using default value 1
First sector (2048-524287999, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-524287999, default 524287999): 507516925

Command (m for help): p

Disk /dev/sda: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 cylinders, total 524288000 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: 0x000e49fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   507516925   253757439   83  Linux

Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): e
Partition number (1-4, default 2): 2
First sector (507516926-524287999, default 507516926):
Using default value 507516926
Last sector, +sectors or +size{K,M,G} (507516926-524287999, default 524287999):
Using default value 524287999

Command (m for help): p

Disk /dev/sda: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 cylinders, total 524288000 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: 0x000e49fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   507516925   253757439   83  Linux
/dev/sda2       507516926   524287999     8385537    5  Extended

Command (m for help): n
Partition type:
   p   primary (1 primary, 1 extended, 2 free)
   l   logical (numbered from 5)
Select (default p): l
Adding logical partition 5
First sector (507518974-524287999, default 507518974):
Using default value 507518974
Last sector, +sectors or +size{K,M,G} (507518974-524287999, default 524287999):
Using default value 524287999

Command (m for help): p

Disk /dev/sda: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 cylinders, total 524288000 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: 0x000e49fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   507516925   253757439   83  Linux
/dev/sda2       507516926   524287999     8385537    5  Extended
/dev/sda5       507518974   524287999     8384513   83  Linux

Command (m for help): t
Partition number (1-5): 5

Hex code (type L to list codes): 82
Changed system type of partition 5 to 82 (Linux swap / Solaris)

Command (m for help): p

Disk /dev/sda: 268.4 GB, 268435456000 bytes
255 heads, 63 sectors/track, 32635 cylinders, total 524288000 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: 0x000e49fa

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1            2048   507516925   253757439   83  Linux
/dev/sda2       507516926   524287999     8385537    5  Extended
/dev/sda5       507518974   524287999     8384513   82  Linux swap / Solaris

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.

WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

me@ubuntu:~$ sudo reboot

I noticed afterwards that I didn’t set the bootable flag but apparently you don’t really need it.

Third: Enlargen the filesystem.

You can do this with resize2fs online on a mounted partition.

me@ubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        91G   86G   12M 100% /
udev            3.9G  4.0K  3.9G   1% /dev
tmpfs           1.6G  696K  1.6G   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            3.9G  144K  3.9G   1% /run/shm
none            100M   16K  100M   1% /run/user

me@ubuntu:~$ sudo resize2fs /dev/sda1
resize2fs 1.42.5 (29-Jul-2012)
Filesystem at /dev/sda1 is mounted on /; on-line resizing required
old_desc_blocks = 6, new_desc_blocks = 16
The filesystem on /dev/sda1 is now 63439359 blocks long.

me@ubuntu:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1       239G   86G  142G  38% /
udev            3.9G   12K  3.9G   1% /dev
tmpfs           1.6G  696K  1.6G   1% /run
none            5.0M     0  5.0M   0% /run/lock
none            3.9G  152K  3.9G   1% /run/shm
none            100M   36K  100M   1% /run/user

Slight catch: After rebooting the swap space wasn’t active. Turned out you need to run mkswap, adjust /etc/fstab to the new UUID and turn the swap on

me@ubuntu:~$ sudo mkswap /dev/sda5
Setting up swapspace version 1, size = 8384508 KiB
no label, UUID=141d401a-b49d-4a96-9b85-c130cb0de40a
me@ubuntu:~$ sudo swapon --all --verbose
swapon on /dev/sda5
swapon: /dev/sda5: found swap signature: version 1, page-size 4, same byte order
swapon: /dev/sda5: pagesize=4096, swapsize=8585740288, devsize=8585741312

Edit /etc/fstab to replace the UUID for the old swap partition with the new one from mkswap.

10 thoughts on “Live resizing of an ext4 filesytem on linux

  1. Thanks a lot, this was really helpful as I only had remote access to a Debian server. Surprisingly most other tutorials claim that a live root resize is impossible while it’s clearly not.

    Reply
  2. This worked for me as well (VM ubuntu 8.04.4LTS) and the logic behind it should make it sound for pretty much every other flavor. Great work OP

    Reply
  3. Supercool! Has worked like a charm on Ubuntu 12.04LTS. The only thing I changed was to run partprobe instead of rebooting. I had to resize the filesystem of a host computer with mutliple virtualbox instances running on it, so rebooting would have been a bother. However, doing first a partprobe and then the resize2fs did the job, and the system appears to be stable after the change. Thank you very much for sharing this!

    Reply
  4. Pingback: Build your own CDH5 QuickStart VM with Spark on CentOS | Denny Lee

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s