Ubuntu – How to create a swap for Azure Ubuntu VM

azurecloud-initUbuntu

I have read quite a few posts on this, but I am still unsure about the correct approach, assuming:

I have a default Ubuntu 14.04 LTS VM created by and running on Azure, which doesn't come with a swap
I would like to create a swap using existing VM storage, instead of create a new disk using additional storage

Posts I have read:

Many solutions were discussed but I can't seem to find one that will persists across server reboots (probably due to cloud-init has it's own idea about image partitioning), can someone advise me on the best practice?

Best Answer

Assuming that you have Linux Agent installed. All you have to do is to enable swap under /etc/waagent.conf. These are the relevant lines:

ResourceDisk.Format=y                   # Format if unformatted. If 'n', resour$
ResourceDisk.Filesystem=ext4            # Typically ext3 or ext4. FreeBSD image$
ResourceDisk.MountPoint=/mnt/resource   #
ResourceDisk.EnableSwap=y               # Create and use swapfile on resource d$
ResourceDisk.SwapSizeMB=2048            # Size of the swapfile.

It will automatically use the resource disk (which comes with every VM) to create the swap. There's no need to create a disk for it.

Update: You also need to execute the steps below in order to create the swapfile:

umount /mnt
service walinuxagent restart

Related Solutions

Linux – Why don’t EC2 ubuntu images have swap

You are right, the Ubuntu EC2 EBS images don't come with swap space configured (for 11.04 at least). The "regular" instance-type images do have a swap partition, albeit only 896 MB on the one I tested.

If some process blows up and you don't have swap space, your server could come to a crawling halt for a good while before the OOM killer kicks in, whereas with swap, it merely gets slow. For that reason, I always like to have swap space around, even with enough RAM. Here's your options:

Create an EBS volume (2-4 times the size of your RAM), attach it to your instance (I like calling it /dev/xvdm for "memory"), sudo mkswap /dev/xvdm, add it to fstab, sudo swapon -a, and you're good to go. I have done this before and it works fine, but it is probably a bit slower than instance store because it goes over the network.
Or you might be able to repartition your disk to add a swap partition, though this might require creating a new AMI. I have not been able to do this in a running instance, because I cannot unmount the root file system, and I do not even have access to the disk device (/dev/xvda), only the partition (xvda1).
Or you can create a swap file. This is my preferred solution right now.
```
sudo dd if=/dev/zero of=/var/swapfile bs=1M count=2048 &&
sudo chmod 600 /var/swapfile &&
sudo mkswap /var/swapfile &&
echo /var/swapfile none swap defaults 0 0 | sudo tee -a /etc/fstab &&
sudo swapon -a
```
Done. :) I know a lot of people feel icky about using files instead of partitions, but it certainly works well enough as emergency swap space.

Ubuntu – open port on ubuntu in azure

You'll need to add it as an endpoint instead. From the Windows Azure preview portal, select Virtual Machines -> Your virtual machine. Then click the endpoints tab and finally New. You can see there that only SSH port is open by default.

Best Answer

Related Solutions

Linux – Why don’t EC2 ubuntu images have swap

Ubuntu – open port on ubuntu in azure

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