mergerfs/mkdocs/docs/setup/upgrade.md

# Upgrade

mergerfs can be upgraded live by mounting on top of the previous
instance. Simply install the new version of mergerfs and follow the
instructions below.

Run mergerfs again or if using `/etc/fstab` call for it to mount
again. Existing open files and such will continue to work fine though
they won't see runtime changes since any such change would be the new
mount. If you plan on changing settings with the new mount you should
/ could apply those before mounting the new version.

```
$ sudo mount /mnt/mergerfs
$ mount | grep mergerfs
media on /mnt/mergerfs type mergerfs (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other)
media on /mnt/mergerfs type mergerfs (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other)
```

A problem with this approach is that the underlying instance will
continue to run even if the software using it stop or are
restarted. To work around this you can use a "lazy umount". Before
mounting over top the mount point with the new instance of mergerfs
issue: `umount -l <mergerfs_mountpoint>`. Or you can let mergerfs do
it by setting the option `lazy-umount-mountpoint=true`.