Can you expand a HDD on an online Linux VM?

On Windows since at least 2008, you have been able to expand a disk on a running virtual machine in VMware (or any other virtualization/SAN LUN) and then expand the disk/volume within Windows without needing downtime/maintenance.

We have SLES 11 VM’s with ext3 partitions in their LUNs. I’m sure that there has to be a way to do this. Is this possible with ext3, do I need to be using ext4, LVM, btrfs, I don’t know. I keep searching for this on the web and as soon as I think I’ve found the answer there is a “now, reboot the virtual machine” in it. Sorry I don’t have as much Linux experience as I do in Windows.

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jibbajabba

If you don't have LVMs the. You need some downtime as it requires deleting and recreating the partition table and unless you know what you are doing (and tested guides on a test VM) you likely end up with a broken system (snapshots help of course). Now IF the server in question has LVMs and the 'drive' you need expanding is indeed a logical volume, then you are lucky. Expanding a volume can be done online, without reboot. However, not many Linux systems recognise a drive change / increase without a reboot (reboot takes minutes if not seconds though, beauty of a VM).

However, there are ways to rescan the SCSI bus, which MAY cause Linux to recognise the increased / added VMDK.

One way is explained here, post 2

linux: rescan disk geometry for resized virtual... | VMware Communities

Each distro is different though so better Google a bit more