I want to run unshare, mount a few directories, and run a tmux session in the new mount namespace. Here is my setup
$ cat run
#!/bin/bash
mount --bind ~/a ~/b
tmux
$ unshare -r --mount ~/run
When I run this command, I get dropped into the tmux session but without the binding. What is more strange to me is that if I rerun the mount command in the tmux session and exit, the next time I run unshare -r --mount ~/run the binding is there!
I could get consistent behavior by always running the mount command in the tmux session but I would like to understand why the behavior depends on if the binding existed in a previous session.
Replacing tmux with /bin/bash to poke at the mounted directory shows that the binding always happens, as expected. Once running the mount command in tmux, all subsequent runs have the binding until I move ~/a. Then the problem is back.
I am now unable to reproduce my own problem. I suspect the solution was to power cycle. I do not think I had done so between installing tmux and running into this issue, so that may have been the root cause.