Volumes
Volumes are extra storage you can attach to your virtual machine.
Let’s take a look at the current status of our virtual machine, by using the lsblk tool. This tool will show any block devices available.
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 252:0 0 10G 0 disk
└─vda1 252:1 0 10G 0 part /
From the output above, we can see that we have a single 10GB disk available called vda. This is the root disk that is provided by our Instance flavor we chose in an earlier step. This block device has one partition vda1 which is mounted to /, which is our root filesystem.
Using the df tool, we can get a better look at the filesystem. We pass the -h argument to show us human readable sizes and / as the last argument to only show us the root filesystem mounted at /.
df -h /
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 9.9G 1.1G 8.4G 12% /
So we currenly have 8.4G of storage available on our new Instance. Depending on the type of workload that this instance might run, that might not be enough.
Creating a new volume
To create a new volume, select Project > Volumes -> Volumes from the left-hand navigation panel. Click the Create Volume button to get started.
From the Create Volume form, you should specify a Name and a Size for your new volume. It is also very important to select the Availability Zone that matches the Availability Zone that your Instance has been launched in. A Volume can only be attached to an Instance if their Availability Zones match.
Attaching the volume
Once the Volume has been created, click the down arrow of Actions menu next to your new volume, and choose Manage Attachments. From the form, you can choose to attach the volume to your instance. Find your Instance from the list, and click the Attach button.
The status should change to indicate the Volume has now been attached to your new instance, and this should be reflected within our Instance.
lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 252:0 0 10G 0 disk
└─vda1 252:1 0 10G 0 part /
vdb 252:16 0 1G 0 disk
As we can now see, there is a new 1GB disk attached called vdb with no partitions.
Creating a filesystem
To make this storage usable, we need to create a filesystem on this device, if one doesn’t already exist. In this case, we’re certain that the device doesn’t already contain a filesystem.
We’re going to use the lsblk command again, but pass the --fs option to show us any filesystem information.
lsblk --fs
NAME FSTYPE LABEL UUID MOUNTPOINT
vda
└─vda1 ext4 3bd4d5a4-a8ce-4584-acda-28d323c0ec99 /
vdb
This shows us that vdb does not have a filesystem on it yet, so we should go ahead and create one. We’re going to use the standard ext4 filesystem for our Volume. There are other choices we could make, depending on our requirements, but ext4 is a good choice for general workloads. Note that we need to prefix this command with sudo as we’ll require superuser privileges.
sudo mkfs -t ext4 /dev/vdb
mke2fs 1.44.1 (24-Mar-2018)
Creating filesystem with 262144 4k blocks and 65536 inodes
Filesystem UUID: cd8d17cb-20f2-469b-9ff5-8ab2d1db2856
Superblock backups stored on blocks:
32768, 98304, 163840, 229376
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
Running our lsblk command again shows that we’ve successfully created a filesystem on our device.
lsblk --fs
NAME FSTYPE LABEL UUID MOUNTPOINT
vda
└─vda1 ext4 3bd4d5a4-a8ce-4584-acda-28d323c0ec99 /
vdb ext4 cd8d17cb-20f2-469b-9ff5-8ab2d1db2856
Take note of that UUID value for our new filesystem on the vdb device.
Mounting the volume
The first step is to prepare our mount point. This will be the location to where our new Volume’s filesystem will be available. In this example, we’re going to use the path /mnt/data.
We’re going to create directory for this using the mkdir command. The -p argument creates any preceeding directories if they don’t already exist, and the last argument is the path to create.
sudo mkdir -p /mnt/data
Let’s now mount our filesystem to this new path, using the mount command. We need to pass it the device (which is vdb) and the path to where it should be mounted.
sudo mount /dev/vdb /mnt/data
Coming back to our df tool, we can now see the status of the filesystem we created on our Volume now mounted and available for use.
df -h /mnt/data
Filesystem Size Used Avail Use% Mounted on
/dev/vdb 976M 2.6M 907M 1% /mnt/data
Auto mounting our filesystem
To ensure the filesystem is mounted on boot, we need to add an entry for it to the /etc/fstab file.
Our entry is in the following format:
device_name mount_point file_system_type fs_mntops fs_freq fs_passno
So in our case, we’ll add the following line to our /etc/fstab file.
UUID=cd8d17cb-20f2-469b-9ff5-8ab2d1db2856 /mnt/data ext4 defaults,nofail 0 2
The UUID is the value we discovered earlier corresponding to our new filesysten on vdb. Explaining all the values here are out of scope for this example, but if you’re interested in what these values mean, you should consult the fstab manual page by typing man fstab.
Now, we’ll edit the file using the nano editor with superuser priviliges.
sudo nano /etc/fstab
Add our new entry to the bottom of the file. Once you’re happy, press Ctrl+X to exit, and type Y to save, and hit enter to accept the default file name.
To confirm the changes to the file are valid, we can run the mount -a command, again with superuser priviliges.
sudo mount -a
If everything is correct, you should see no output.