Resizing a disk on a cloud compute instance (AWS or Google)

Resizing a disk on a cloud compute instance

Diagnosis

If you get an error when installing/upgrading a package that looks like this:

dpkg: error processing archive /var/cache/apt/archives/linux-image-3.13.0-62-generic_3.13.0-62.102_amd64.deb (--unpack):
 cannot copy extracted data for './boot/vmlinuz-3.13.0-62-generic' to '/boot/vmlinuz-3.13.0-62-generic.dpkg-new': failed to write (No space left on device)

...then your root file system is full. This can also be checked like this:

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/xvda1            129G   129G   0M 100% /

If this has happened, one way to proceed is to add a new file system and move data to it (e.g. so that /home is a separate file system that is mounted into the tree but not using any of the allocated space on the root file system any more).  This method is not covered here.

Another way is to expand the size of the existing root file system.  That is what this article covers.  The phases below apply to any file system that has become full.  (No longer do you need to shut down the instance or unmount the file system, snapshot the volume and create a new, larger one from the snapshot.)

How to fix 

Warning: A mistake or mis-interpretation when following these steps could destroy your data.  Please use caution, and unless you are an intermediate or above Linux user, consider asking a system administrator who is familiar with the tools presented to perform the task.

Phase 1 -- Expand virtual disk

If you are using Amazon Web Services:

1. Log in to the AWS console
2. Make sure you are in the EC2 service section
3. Click on Volumes in the left-hand menu
4. Find the volume that is attached to your instance (sort by the Attachment column)
• Ensure you have found the correct one if that instance has multiple volumes
5. Right-click on the volume and choose Modify
6. Alter the size
7. Click [Save]

 If you are using Google Compute Engine:

1. Log in to the console
2. In the drop-down menu, choose the project that your compute instance belongs to
3. In the Resources box, click on Compute Engine
4. Click on the name of your instance in the list
5. Scroll down to the "Boot disk and local disks" section
6. Click on the relevant disk
7. Click [EDIT] in the toolbar
8. Change the Size value
9. Click [Save]

Other virtualisation systems (like VMware) or storage management systems (like LVM), may allow you to expand a disk volume.  If your host uses one of these systems, research and apply whatever method is available to you, then continue with the next phases.

Phase 2a -- Expand partition

In the steps below, replace /dev/sda with the device name of the root file system, minus the partition number.

1. Log in via SSH 
2. Run lsblk to determine the device of the root file system
• See examples below
• The device name is given in the first column, and in this case is not preceded with "/dev/"
• The relevant disk or partition is the one with "/" in the MOUNTPOINT column
3. If the root file system's device is a disk (not a partition) skip to "Phase 3 -- Expand file system"
• Virtual disks under Linux have device names like "/dev/sda" or "/dev/xvdf"
• Partitions are a way of subdividing disks; they have device names like "/dev/sda1" or "/dev/xvdf2"
• A file system can reside on a partition or use the whole disk; in the latter case there is no partition table and so trying to list/manipulate it won't work
4. Tell Linux to detect the new disk size
1.  N/A -- this is done automatically by the kernel
5. Install parted
1.  Run "sudo apt-get update ; sudo apt-get install parted"
6. Run parted to expand the partition
1. Run "sudo parted /dev/sda"
• Observe the note above about /dev/sda
2. Check if there is more than one partition on the disk:
1. At the parted prompt, Run "print list"
• Take note of the disk size displayed on the second line of output
2. If the root file system's partition (see step 2) is not the last one on the disk, follow the steps at "Phase 2b -- Moving and expanding partitions" and then return here.
3.  At the parted prompt, Run "resize 1 start size"
• If appropriate, replace "1" with the root file system's partition number
• Replace "start" with the partition's existing Start value from the table show by "print list" above
• Replace "size" with the disk size value noted above
4. Follow the instructions provided by parted
5. At the parted prompt, Run "quit"
7. Tell Linux to update its view of the partitions
1.  Run "sudo kpartx -u /dev/sda"
• Observe the note above about /dev/sda

lsblk examples

$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
xvda 202:0    0  15G  0 disk /

 or:

$ lsblkNAME   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda      8:0    0  10G  0 disk
└─sda1   8:1    0  10G  0 part /

Phase 2b -- Moving and expanding partitions

Warning: Skip to Phase 3 unless Phase 2a directed you to follow these steps.

TBA

Phase 3 -- Expand file system

This is unnecessary if your root file system's device is a partition, as you will have resized both in Phase 2.

Firstly, run "df -hT" and take note of the value for the root file system in the Type column.

If the file system type is ext4, follow these steps:

1. Run "sudo apt-get update ; sudo apt-get install e2fsprogs"
2. Run "sudo resize2fs /dev/sda"
• Observe the note in Phase 2a about /dev/sda
3. Follow the instructions provided

 If the file system type is xfs, follow these steps:

1. Run "sudo apt-get update ; sudo apt-get install xfsprogs"
2. Run "sudo xfs_growfs /dev/sda"
• Observe the note in Phase 2a about /dev/sda
3. Follow the instructions provided

If the file system type is rootfs, look for the other line in the df output that is also mounted on "/" (don't ask me why there's two) and follow the steps above for that file system type.

If  the file system type is none of the above, do a web search for the type and the word "resize".

Phase 4 -- Verification

Run "df -h" and you should see that you now have plenty of free space on your root file system.