ZFS FAQ

How do I remount a filesystem in read/write mode? zfs set readonly=off zroot

How do I mount all filesystems? zfs mount -a

Recovering EFI boot partition

If your boot loader gets corrupted, you can boot off of MidnightBSD install media for your release and do the following from the live cd functionality.

(replace nvd0 with your disk. EFI should be on the first partition)

(more destructive, can wipe custom configurations here) gpart bootcode -p /boot/boot1.efifat -i 1 nvd0

In some cases, you can simply copy the loader.efi (after mounting it) mount_msdosfs /dev/nvd0p1 /mnt cp /boot/loader.efi /mnt/efi/boot/BOOTx64.efi

NFS

Setup NFS shares

zfs set sharenfs="-maproot=0 -network 192.168.0.0/24" zroot/my/path

service mountd restart

Verify configuration

zfs get sharenfs zroot/my/path

Note that any entries from sharenfs commands get placed in /etc/zfs/exports

Setting up multiple subnets

note the new lines INSIDE the quotes

zfs set sharenfs="-maproot=root -network 10.0.0.0/24 
> /path/to/mountpoint -maproot=root -network 192.168.0.0/24 
> /path/to/mountpoint -maproot=root -network 172.16.0.0/24" pool0/space

Tuning

Tuning for PostgreSQL

many guides recommend 8K or 16K for recordsize with postgresql. There are some benchmarks showing better results with 16K, but most favor 8k as that aligns with default block sizes in PG.

zfs set recordsize=8K tank/usr/local/pgsql

zfs set primarycache=metadata  tank/usr/local/pgsql

zfs set logbias=throughput  tank/usr/local/pgsql

zfs set redundant_metadata=most  tank/usr/local/pgsql

Tuning for large files

Setting a larger recordsize can be quite beneficial for large files such as videos.

zfs set recordsize=1M tank/media/video

Deduplication

It's usually a bad idea to use deduplication unless you have a lot of RAM or a very small file system. The minimum is usually around 5GB of RAM per 1TB of disk.

ZFS send / receive

To receive data as a non root user, myuser:

zfs allow myuser mount,create,receive vm/vm

To send, first snapshot then send

zfs snapshot vm/vm/m3164b@luke
zfs send vm/vm/m3164b@luke | ssh myuser@myhost zfs recv vm/vm/m3164