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I've created btrfs system on USB stick, copied about 2GB of files via GUI (Nemo, Linux Mint 20), ejected via GUI. Inserted in another PC, but have not seen these files. I've checked df -h output and partition via GUI: df shows several megabytes used, GUI shows 2.2 GB used. How to find the files? I wanted to start to use btrfs more, e.g. for replication/backups as I've read many recommend, but I'm wary when I see files disappear.

I've read Why does size and used space in df output contradict available space, df and Nemo show about same on both devices, hence answer than some process holds to the files I consider not applicable and another "By default, ext2, ext3 and ext4 filesystems reserve 5% of their capacity for use by the root user." also as it is not ext filesystem.

I've run btrfs check, output showed no issues.

df -h
/dev/sdb1        57G  3,8M   55G   1% /media/alex/usb

$ sudo btrfs check --force /dev/sdb1
Opening filesystem to check...
WARNING: filesystem mounted, continuing because of --force
Checking filesystem on /dev/sdb1


[1/7] checking root items
[2/7] checking extents
[3/7] checking free space cache
[4/7] checking fs roots
[5/7] checking only csums items (without verifying data)
[6/7] checking root refs
[7/7] checking quota groups skipped (not enabled on this FS)
found 393216 bytes used, no error found
total csum bytes: 0
total tree bytes: 131072
total fs tree bytes: 32768
total extent tree bytes: 16384
btree space waste bytes: 124727
file data blocks allocated: 262144
 referenced 262144

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Martian2020
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  • Does the other PC see the partition on the USB stick? Does the other PC have the same version of btrfs tools? – rickhg12hs Dec 06 '21 at 00:13
  • @rickhg12hs, yes, sees. I use Linux Mint 20 now mostly as OS, I have not installed additional btrfs tools. If Linux of slightly different versions of tools and/or kernel results in files missing that is no-go for me for that fs. I've encountered some time ago that kernel 3 does not read ext4 from kernel 5 (due to new journaling), but I was "told" by the system that partition cannot be opened, not just empty folder. P.S. maybe btrfs needs to be synced and unmounted from terminal as GUI support for in is not "perfect". – Martian2020 Dec 06 '21 at 04:01
  • I haven't "passed around" btrfs partitions by USB stick before, but I do pass them between several VMs that have different Linux distros, etc., and I've not seen what you are experiencing. I don't use Mint or Nemo, but I hope they properly sync/umount filesystems before ejecting them. If you manually sync/umount/eject, is everything there? – rickhg12hs Dec 06 '21 at 21:00

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