Expand root zpool while online

When the physical zvol has increased in capacity, ZFS should expand to use all the extra space. However this usually requires a re-mount which also means a reboot if your zpool is used for the root filesystem.

There is a command I found that works around this limitation, usually used for bringing new disks into a running zpool.

zpool online -e zroot <disk>

This should cause the zpool to recognise the new storage area immediately.

A re-mount may be a safer way to do this however if that is possible and a reboot is not so much of a problem.