I backup my hard drive through sudo zfs send snapshot | sudo tee /my-mount-point/my-snapshot.zfs > /dev/null, and I want to make sure that I don't accidentally unmount (and turn off) /my-mount-point.

Now, had I cd into there, it wouldn't be a problem, as I would get umount: /my-mount-point: target is busy.. But with tee, it doesn't do that.

Moreover, when I try running lsof | grep "my-mount-point", I get nothing. If I cd into my-mount-point, lsof will show it. Otherwise, nothing.

Is there a way to get if something's writing to a file under my-mount-point?

  • As a side note, your command line is strange. Since you don't output the backup to stdout, you don't need tee, sudo zfs send snapshot > /my-mount-point/my-snapshot.zfs is enough, isn't it?
    – Amessihel
    Jun 30, 2020 at 19:27
  • @Amessihel not if /my-mount-pointt isn't user writable
    – unix
    Jun 30, 2020 at 21:40
  • Even with the sudo call, you're sure?
    – Amessihel
    Jun 30, 2020 at 21:45

1 Answer 1


Why not CD-ing into that directory before backing up your HD?

cd /my-mount-point/ &&
(sudo zfs send snapshot | 
 sudo tee my-snapshot.zfs > /dev/null) && cd

Sounds to be the easiest way to get a CWD under your mount point.

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