On 13.09.2018 19:15, Serhat Sevki Dincer wrote: >> -1 seems to be EPERM, is your device write-protected, readonly or >> something like that ? > > I am able to use ext4 partition read/write, created a file and wrote > in it, un/re mounted it, all is ok. > The drive only has a microusb port and a little led light; no rw > switch or anything like that.. > What might help is running btrfs convert under strace. So something like : sudo strace -f -o strace.log btrfs-convert /dev/sdb1 and then send the log.
