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If a user owning a VM with a Bootable Volume needs to resize it to make it bigger (never SMALLER, in order to avoid breaking the VM), they can perform the operation themselves via Openstack Dashboard:
Checking there is enough free space usable on their tenant;
Shutting down the VM;
Clicking on the Bootable Volume, then on Extend Volume inside the right menu, writing there the desired new volume size;
Rebooting the VM and check that the volume has the correct size, using the command
df -h.
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