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A common usage pattern for zgenhostid, including in the ZFS dracut module, is running it as: zgenhostid $(hostid) However, zgenhostid only accepted hostid arguments greater than 0, which meant that, when the output of hostid(1) was "00000000", zgenhostid would error out, even though 0 is a possible return value for the gethostid(3) function used by hostid(1): - On current musl libc, gethostid(3) is a stub that always returns 0. - On glibc, gethostid(3) will return 0 if /etc/hostid exists but is smaller than 4 bytes. In these cases, it makes more sense for zgenhostid to treat a value of 0 as other parts of the zfs codebase do, meaning that a hostid value couldn't be determined; therefore, it should attempt to generate a random value to write into /etc/hostid. The manpage and usage output have been updated to reflect this. Whitespace has also been fixed in the usage output. Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Georgy Yakovlev <gyakovlev@gentoo.org> Reviewed-by: Andrew J. Hesford <ajh@sideband.org> Signed-off-by: Érico Rolim <erico.erc@gmail.com> Closes #11174 Closes #11189
104 lines
2.5 KiB
Groff
104 lines
2.5 KiB
Groff
.\"
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.\" CDDL HEADER START
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.\"
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.\" The contents of this file are subject to the terms of the
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.\" Common Development and Distribution License (the "License").
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.\" You may not use this file except in compliance with the License.
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.\"
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.\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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.\" or http://www.opensolaris.org/os/licensing.
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.\" See the License for the specific language governing permissions
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.\" and limitations under the License.
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.\"
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.\" When distributing Covered Code, include this CDDL HEADER in each
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.\" file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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.\" If applicable, add the following below this CDDL HEADER, with the
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.\" fields enclosed by brackets "[]" replaced with your own identifying
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.\" information: Portions Copyright [yyyy] [name of copyright owner]
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.\"
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.\" CDDL HEADER END
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.\"
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.\"
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.\" Copyright (c) 2017 by Lawrence Livermore National Security, LLC.
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.\"
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.Dd September 13, 2020
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.Dt ZGENHOSTID 8 SMM
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.Os
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.Sh NAME
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.Nm zgenhostid
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.Nd generate and store a hostid in
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.Em /etc/hostid
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.Sh SYNOPSIS
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.Nm
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.Op Fl f
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.Op Fl o Ar filename
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.Op Ar hostid
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.Sh DESCRIPTION
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Creates
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.Pa /etc/hostid
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file and stores hostid in it.
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If the user provides
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.Op Ar hostid
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on the command line, validates and stores that value.
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Otherwise, randomly generates a value to store.
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.Bl -tag -width "hostid"
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.It Fl h
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Display a summary of the command-line options.
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.It Fl f
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Force file overwrite.
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.It Fl o Ar filename
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Write to
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.Pa filename
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instead of default
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.Pa /etc/hostd
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.It Ar hostid
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Specifies the value to be placed in
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.Pa /etc/hostid .
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It should be a number with a value between 1 and 2^32-1.
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If it is 0, zgenhostid will generate a random hostid.
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This value
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.Sy must
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be unique among your systems.
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It
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.Sy must
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be expressed in hexadecimal and be exactly
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.Em 8
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digits long, optionally prefixed by
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.Em 0x .
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.El
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.Sh FILES
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.Pa /etc/hostid
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.Sh EXAMPLES
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.Bl -tag -width Bd
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.It Generate a random hostid and store it
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.Bd -literal
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# zgenhostid
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.Ed
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.It Record the libc-generated hostid in Pa /etc/hostid
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.Bd -literal
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# zgenhostid "$(hostid)"
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.Ed
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.It Record a custom hostid (0xdeadbeef) in Pa /etc/hostid
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.Bd -literal
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# zgenhostid deadbeef
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.Ed
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.It Record a custom hostid (0x01234567) in Pa /tmp/hostid
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and ovewrite the file if it exists
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.Bd -literal
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# zgenhostid -f -o /tmp/hostid 0x01234567
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.Ed
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.El
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.Sh SEE ALSO
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.Xr genhostid 1 ,
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.Xr hostid 1 ,
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.Xr sethostid 3 ,
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.Xr spl-module-parameters 5
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.Sh HISTORY
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.Nm
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emulates the
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.Xr genhostid 1
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utility and is provided for use on systems which
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do not include the utility or do not provide
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.Xr sethostid 3
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call.
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