Boot a gparted iso and resize it from there. Trying to do it command line only, without installing anything is just going to be suffering.
this post was submitted on 14 Jan 2026
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Here it is, the dumb question: How can I boot from an iso to modify a VM's partitions? Further, would the VM's / dir need to be unmounted first to resize it? Thanks for the guidance.
Just configure your VM to boot the gparted iso. What virtulization software are you using? If it's proxmox on your VM there's the options on the side bar, then boot order. Just untick the main boot drive and only have the CD drive bootable until you're done resizing.
When you reboot nothing is mounted because it's off. Boot gparted and it will handle everything.
Since you're using docker, also ensure your containers are set to rotate log files. By default, docker does not enable this, but you can change the defaults. Otherwise you can quickly get gigabytes of logs that eat up space.
I really don't wanna sound like an asshole, but based on the question and its style, you'll fuck something up and lose data. there's too many moving targets in your stack; put aside the idea that a beginner is dicking around with proxmox (why!?)
exfil data, nuke the thing, create a new one sized right, import data, done.
if you really wanna have at it, add a live ISO to proxmox boot order for that VM, boot off it and once you get the desktop use KDE Partition Manager or Gparted to expand the file system. after you're done, shut down the VM, remove the live ISO and put the old boot order back in.
then, maybe, get rid of proxmox and have a regular debian server with a buncha docker services where you'll never have to pre-allocate virtual disks and such. good luck!
put aside the idea that a beginner is dicking around with proxmox (why!?)
Fun :)
But seriously, I wanted to throw myself into it to see if I could learn it. I totally get the impulse to question a beginner's choice for promox; I am questioning it too, frankly. I may follow your advice of restarting that server, but the thought of setting everything up again hurts my soul... At least I know how, though!
Thanks for the kind response.
I jumped into proxmox blind. Make a full backup and blow that shit up. Break things, have fun, roll it back.
Get a gparted iso, boot into it, resize shit and if it fucks up, restore from backup and try again.