Reorganize zfs(8) man page into sections

Most subcommands got their own manpages (e.g. create). Some related
commands grouped into a single manpage and symlinks created (e.g. set, 
get, and inherit). I did this when topics were either too short to 
warrant their own file or so interrelated that a user would want to
refer between commands in the same file.

Corrected .Sx internal references to .Xr cross refs; lots of .Sx 
references from when text was all in zfs.8 needed to be changed to 
.Xr zfs-$SUBCOMMAND 8 cross references.

Divided subcommand list in zfs(8) into sections of related 
functionality. This required writing new descriptions for some 
commands.

Preserved ".Os Linux", `.Os` macro parsing behavior differs between 
mandoc from the "BSD" mandoc package (available on Ubuntu) and man 
from Ubuntu's man-db package, which calls groff to format the manpages.

Groff handles the `.Os` macro differently and wrongly, defaulting 
it to "BSD" in `/usr/share/groff/*/tmac/mdoc/doc-common`, instead of
getting the default from `uname`.

A future set of changes will introduce build-time preprocessing of
manpages for platform-specific documentation and can insert the
correct operating system name.

Added SEE ALSO sections, the newly-divided zfs-*.8 subcommand man
pages needed their own SEE ALSO sections pointing to related
subcommands and, in some cases, documentation from other packages
(e.g. zfs-share.8).

Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Kjeld Schouten <[email protected]>
Reviewed-by: Sean Eric Fagan <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: Ross Williams <[email protected]>
Closes #9559 

1 files changed, 110 insertions, 0 deletions

diff --git a/man/man8/zfs-hold.8 b/man/man8/zfs-hold.8
new file mode 100644
index 000000000..200c17ebf
--- /dev/null
+++ b/man/man8/zfs-hold.8
@@ -0,0 +1,110 @@
+.\"
+.\" CDDL HEADER START
+.\"
+.\" The contents of this file are subject to the terms of the
+.\" Common Development and Distribution License (the "License").
+.\" You may not use this file except in compliance with the License.
+.\"
+.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+.\" or http://www.opensolaris.org/os/licensing.
+.\" See the License for the specific language governing permissions
+.\" and limitations under the License.
+.\"
+.\" When distributing Covered Code, include this CDDL HEADER in each
+.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+.\" If applicable, add the following below this CDDL HEADER, with the
+.\" fields enclosed by brackets "[]" replaced with your own identifying
+.\" information: Portions Copyright [yyyy] [name of copyright owner]
+.\"
+.\" CDDL HEADER END
+.\"
+.\"
+.\" Copyright (c) 2009 Sun Microsystems, Inc. All Rights Reserved.
+.\" Copyright 2011 Joshua M. Clulow <[email protected]>
+.\" Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
+.\" Copyright (c) 2014, Joyent, Inc. All rights reserved.
+.\" Copyright (c) 2014 by Adam Stevko. All rights reserved.
+.\" Copyright (c) 2014 Integros [integros.com]
+.\" Copyright 2019 Richard Laager. All rights reserved.
+.\" Copyright 2018 Nexenta Systems, Inc.
+.\" Copyright 2019 Joyent, Inc.
+.\"
+.Dd June 30, 2019
+.Dt ZFS-HOLD 8
+.Os Linux
+.Sh NAME
+.Nm zfs Ns Pf - Cm hold
+.Nd Hold a snapshot to prevent it being removed with the zfs destroy command.
+.Sh SYNOPSIS
+.Nm
+.Cm hold
+.Op Fl r
+.Ar tag Ar snapshot Ns ...
+.Nm
+.Cm holds
+.Op Fl rH
+.Ar snapshot Ns ...
+.Nm
+.Cm release
+.Op Fl r
+.Ar tag Ar snapshot Ns ...
+.Sh DESCRIPTION
+.Bl -tag -width ""
+.It Xo
+.Nm
+.Cm hold
+.Op Fl r
+.Ar tag Ar snapshot Ns ...
+.Xc
+Adds a single reference, named with the
+.Ar tag
+argument, to the specified snapshot or snapshots.
+Each snapshot has its own tag namespace, and tags must be unique within that
+space.
+.Pp
+If a hold exists on a snapshot, attempts to destroy that snapshot by using the
+.Nm zfs Cm destroy
+command return
+.Er EBUSY .
+.Bl -tag -width "-r"
+.It Fl r
+Specifies that a hold with the given tag is applied recursively to the snapshots
+of all descendent file systems.
+.El
+.It Xo
+.Nm
+.Cm holds
+.Op Fl rH
+.Ar snapshot Ns ...
+.Xc
+Lists all existing user references for the given snapshot or snapshots.
+.Bl -tag -width "-r"
+.It Fl r
+Lists the holds that are set on the named descendent snapshots, in addition to
+listing the holds on the named snapshot.
+.It Fl H
+Do not print headers, use tab-delimited output.
+.El
+.It Xo
+.Nm
+.Cm release
+.Op Fl r
+.Ar tag Ar snapshot Ns ...
+.Xc
+Removes a single reference, named with the
+.Ar tag
+argument, from the specified snapshot or snapshots.
+The tag must already exist for each snapshot.
+If a hold exists on a snapshot, attempts to destroy that snapshot by using the
+.Nm zfs Cm destroy
+command return
+.Er EBUSY .
+.Bl -tag -width "-r"
+.It Fl r
+Recursively releases a hold with the given tag on the snapshots of all
+descendent file systems.
+.El
+.El
+.Sh SEE ALSO
+.Xr zfs-destroy 8