System information

Type | Version/Name
--- |master
Distribution Name | ubuntu
Distribution Version | 20.3
Linux Kernel | 5.4.0-42-generic
Architecture |Intel 64
ZFS Version | 0.8.3-1ubuntu12.1
SPL Version | modinfo spl | grep -iw version

Describe the problem you're observing

Despite many reports, documentation on sharenfs still doesn't describe what it does.

Describe how to reproduce the problem

man zfs

Include any warning/errors/backtraces from the system logs

Here's what I suggest: The sharenfs property can be "on", "off" or a list of options. "on" is equivalent to "rw,crossmnt". Options other than ro, rw, and sec are accumulated into a single list, which is used for all exports. That means there is no way to use different options with different hosts or groups of hosts, other than "ro", "rw", and "sec." Most options are used as is with the Linux exportfs command. "ro" or "ro=hostlist" generates a readonly export. Without a hostlist (i.e. "ro" alone) the export goes to all hosts. Similarly, "rw" or "rw=hostlist" generates a readwrite export. The export include all options that appear in the property, except "sec", "rw" and "ro", plus the most recent version of sec appearing before the "ro" or "rw". If no "sec" option has appeared, "sec=sys" is used. hostlist may be a single hostspec or a list separated by colons. Each hostspec can be as in /etc/exports, i.e. hostname(s), IP addresses or ranges, netgroups. A leading @ in the hostspec is skipped, for compatibility with Solaris IP ranges. Thus a netgroup must be specified as @@netgroup. Because of the use of : as a separator, there is no reliable way to specify an IPV6 range.