#!/bin/sh
set -e
# The hostname and hostid of the last system to access a ZFS pool are stored in
# the ZFS pool itself.  A pool is foreign if, during `zpool import`, the
# current hostname and hostid are different than the stored values thereof.
#
# The hostid on Solaris is intrinsic, but is not on Linux (see #595790), so the
# spl kernel module invokes /usr/bin/hostid from the userland in its initialization
# routine.
#
# /usr/bin/hostid will return the 4 first bytes of the file /etc/hostid.
# If this file is not present or contains less than 4 bytes, then /usr/bin/hostid
# will return the bytes of the IP address of $(hostname) flipped, or zero if
# such IP couldn't be obtained
#
# This means that things like a DHCP lease change can affect the hostid.
#
# Therefore the only way of having a stable hostid is to define it on /etc/hostid.
# This postinst helper will check if we already have the hostid stabilized by
# checking the existence of the file /etc/hostid to be 4 bytes at least.
# If this file don't already exists on our system or has less than 4 bytes, then
# we will stabilize our current hostid by writing its value to /etc/hostid

# Detect if /etc/hostid is a conffile of previous spl package, migrate if yes
# hostid file should preserve even when package is purged
if $(dpkg-query --showformat='${Conffiles}\n' --show spl >/dev/null 2>&1); then
	dpkg-maintscript-helper rm_conffile /etc/hostid -- "$@"
fi

if [ ! -f /etc/hostid ] || [ $(stat -c %s /etc/hostid) -lt 4 ] ; then

	# Write our current hostid to /etc/hostid
	HOSTID=$(hostid)
	AA=$(echo $HOSTID | cut -b 1,2)
	BB=$(echo $HOSTID | cut -b 3,4)
	CC=$(echo $HOSTID | cut -b 5,6)
	DD=$(echo $HOSTID | cut -b 7,8)

	# Big Endian
	if [ $(echo -n I | od -to2 | awk 'FNR==1{ print substr($2,6,1)}' 2>/dev/null) = 0 ]; then
		# Invoke the printf from coreutils. shell builtin lacks the byte format.
		/usr/bin/printf "\x$AA\x$BB\x$CC\x$DD" >/etc/hostid
	else
	# Little Endian
		/usr/bin/printf "\x$DD\x$CC\x$BB\x$AA" >/etc/hostid
	fi
fi

#DEBHELPER#