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Create a flavour with disk size as 0

asked 2016-09-20 01:59:11 -0600

naggappan gravatar image

Hi I created a flavour with 512mb of ram and root disk size as 0. And launched a ubuntu cloud iamge. So how does it works without a hard disk size?

Also df -h says I have 2.2GB of free space. Can some one explain if the hard disk size is really required to provide or we can use it as 0 and it will expand as it grows .

ubuntu@test-no-root:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on 
udev            241M   12K  241M   1% /dev
tmpfs            49M  332K   49M   1% /run
/dev/vda1       2.2G  786M  1.3G  39% /
none            4.0K     0  4.0K   0% /sys/fs/cgroup
none            5.0M     0  5.0M   0% /run/lock
none            245M     0  245M   0% /run/shm
none            100M     0  100M   0% /run/user

It would eb good if some one explain me from where /dev/vda1 is taken. Also which is best practice to have size 0 and use the vm's or to be used with HDD size minimum 10 or 20 GB provided. Consider that I would be taking snapshots also.

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answered 2016-09-21 03:51:02 -0600

volenbovsky gravatar image

Hi, either you boot from volume (not likely as I see) or see 'special case' of using 0, from ( "Disk Virtual root disk size in gigabytes. This is an ephemeral disk that the base image is copied into. When booting from a persistent volume it is not used. **The “0” size is a special case which uses the native base image size as the size of the ephemeral root volume. "

BR, Konstantin

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answered 2016-09-20 13:30:13 -0600

updated 2016-09-20 13:31:53 -0600

it's ephemeral storage. meaning it exists on the hypervisor under /var/lib/nova/instances until the machine is deleted.

best practice is to size them just like any other disk. right now it's the size of the image itself.

a good place to read about storage would be here:

and the image guide here:

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Asked: 2016-09-20 01:59:11 -0600

Seen: 61 times

Last updated: Sep 20 '16