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.Dd May 26, 2021
.Dt ZGENHOSTID 8
.Os OpenZFS
.
.Sh NAME
.Nm zgenhostid
.Nd generate host ID into /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 the host ID in it.
If
.Ar hostid
was provided, validate and store that value.
Otherwise, randomly generate an ID.
.
.Sh OPTIONS
.Bl -tag -width "-o filename"
.It Fl h
Display a summary of the command-line options.
.It Fl f
Allow output overwrite.
.It Fl o Ar filename
Write to
.Pa filename
instead of the default
.Pa /etc/hostid .
.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
.Sy 0 ,
generate a random ID.
This value
.Em must
be unique among your systems.
It
.Em must
be an 8-digit-long hexadecimal number, optionally prefixed by
.Qq 0x .
.El
.
.Sh FILES
.Pa /etc/hostid
.
.Sh EXAMPLES
.Bl -tag -width Bd
.It Generate a random hostid and store it
.Dl # Nm
.It Record the libc-generated hostid in Pa /etc/hostid
.Dl # Nm Qq $ Ns Pq Nm hostid
.It Record a custom hostid Po Ar 0xdeadbeef Pc in Pa /etc/hostid
.Dl # Nm Ar deadbeef
.It Record a custom hostid Po Ar 0x01234567 Pc in Pa /tmp/hostid No and overwrite the file if it exists
.Dl # Nm Fl f o Ar /tmp/hostid 0x01234567
.El
.
.Sh SEE ALSO
.Xr genhostid 1 ,
.Xr hostid 1 ,
.Xr sethostid 3 ,
.Xr spl 4
.
.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 the
.Xr sethostid 3
function.