mirror_zfs/man/man8/zgenhostid.8
Érico Rolim c4a5e3b90f zgenhostid: accept hostid arguments equal to zero.
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
2020-11-17 12:19:33 -08:00

104 lines
2.5 KiB
Groff

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.\" Copyright (c) 2017 by Lawrence Livermore National Security, LLC.
.\"
.Dd September 13, 2020
.Dt ZGENHOSTID 8 SMM
.Os
.Sh NAME
.Nm zgenhostid
.Nd generate and store a hostid in
.Em /etc/hostid
.Sh SYNOPSIS
.Nm
.Op Fl f
.Op Fl o Ar filename
.Op Ar hostid
.Sh DESCRIPTION
Creates
.Pa /etc/hostid
file and stores hostid in it.
If the user provides
.Op Ar hostid
on the command line, validates and stores that value.
Otherwise, randomly generates a value to store.
.Bl -tag -width "hostid"
.It Fl h
Display a summary of the command-line options.
.It Fl f
Force file overwrite.
.It Fl o Ar filename
Write to
.Pa filename
instead of default
.Pa /etc/hostd
.It Ar hostid
Specifies the value to be placed in
.Pa /etc/hostid .
It should be a number with a value between 1 and 2^32-1.
If it is 0, zgenhostid will generate a random hostid.
This value
.Sy must
be unique among your systems.
It
.Sy must
be expressed in hexadecimal and be exactly
.Em 8
digits long, optionally prefixed by
.Em 0x .
.El
.Sh FILES
.Pa /etc/hostid
.Sh EXAMPLES
.Bl -tag -width Bd
.It Generate a random hostid and store it
.Bd -literal
# zgenhostid
.Ed
.It Record the libc-generated hostid in Pa /etc/hostid
.Bd -literal
# zgenhostid "$(hostid)"
.Ed
.It Record a custom hostid (0xdeadbeef) in Pa /etc/hostid
.Bd -literal
# zgenhostid deadbeef
.Ed
.It Record a custom hostid (0x01234567) in Pa /tmp/hostid
and ovewrite the file if it exists
.Bd -literal
# zgenhostid -f -o /tmp/hostid 0x01234567
.Ed
.El
.Sh SEE ALSO
.Xr genhostid 1 ,
.Xr hostid 1 ,
.Xr sethostid 3 ,
.Xr spl-module-parameters 5
.Sh HISTORY
.Nm
emulates the
.Xr genhostid 1
utility and is provided for use on systems which
do not include the utility or do not provide
.Xr sethostid 3
call.