hostid

[root@nixos:~]# zfs list
NAME               USED  AVAIL  REFER  MOUNTPOINT
rpool             4.80G  18.3G    96K  /rpool
rpool/home          96K  18.3G    96K  legacy
rpool/root        4.80G  18.3G    96K  none
rpool/root/nixos  4.80G  18.3G  4.80G  legacy

[root@nixos:~]# zpool status
  pool: rpool
 state: ONLINE
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        rpool       ONLINE       0     0     0
          mirror-0  ONLINE       0     0     0
            vda2    ONLINE       0     0     0
            vdb2    ONLINE       0     0     0

errors: No known data errors

[root@nixos:~]# cat /mnt/etc/hostid | od -A none -t x4
 8425e349

[root@nixos:~]# cat /etc/hostid | od -A none -t x4
 8425e349