On Fri, Dec 18, 2020 at 11:49 AM Jeff Moyer <jmoyer@xxxxxxxxxx> wrote: > > Chris Murphy <lists@xxxxxxxxxxxxxxxxx> writes: > > > Hi, > > > > Short version: > > # mkfs.any /dev/vda4 > > unable to open /dev/vda4: Device or resource busy > > > > Curiously /dev/vda4 is just a blank partition, not in use by anything > > that I'm aware of. And gdisk is allowed to modify the GPT on /dev/vda > > without complaint. This is a snippet from strace of the above command > > at the failure point: > > > > openat(AT_FDCWD, "/dev/vda4", O_RDWR|O_EXCL) = -1 EBUSY (Device or > > resource busy) > > [snip] > > > format, and /proc/mounts shows > > > > /dev/vda /run/initramfs/live iso9660 > > ro,relatime,nojoliet,check=s,map=n,blocksize=2048 0 0 > > That mount claims the device, and you can't then also open a partition > on that device exclusively. > > > So it sees the whole vda device as iso9660 and ro? But permits gdisk > > to modify some select sectors on vda? I admit it's an ambiguous image. > > Is it a duck or is it a rabbit? And therefore best to just look at it, > > not make modifications to it. Yet /dev/vda is modifiable, where the > > partitions aren't. Hmm. > > The file system is mounted read-only. It may be that the /device/ is not > read-only. OK super, thanks for the clear explanation. -- Chris Murphy
