debian/spl-dkms.postinst

   1 #!/bin/sh
   2 set -e
   3 # The hostname and hostid of the last system to access a ZFS pool are stored in
   4 # the ZFS pool itself.  A pool is foreign if, during `zpool import`, the
   5 # current hostname and hostid are different than the stored values thereof.
   6 #
   7 # The hostid on Solaris is intrinsic, but is not on Linux (see #595790), so the
   8 # spl kernel module invokes /usr/bin/hostid from the userland in its initialization
   9 # routine.
  10 #
  11 # /usr/bin/hostid will return the 4 first bytes of the file /etc/hostid.
  12 # If this file is not present or contains less than 4 bytes, then /usr/bin/hostid
  13 # will return the bytes of the IP address of $(hostname) flipped, or zero if
  14 # such IP couldn't be obtained
  15 #
  16 # This means that things like a DHCP lease change can affect the hostid.
  17 #
  18 # Therefore the only way of having a stable hostid is to define it on /etc/hostid.
  19 # This postinst helper will check if we already have the hostid stabilized by
  20 # checking the existence of the file /etc/hostid to be 4 bytes at least.
  21 # If this file don't already exists on our system or has less than 4 bytes, then
  22 # we will stabilize our current hostid by writing its value to /etc/hostid
  23
  24 if [ ! -f /etc/hostid ] || [ $(stat -c %s /etc/hostid) -lt 4 ] ; then
  25
  26         # Write our current hostid to /etc/hostid
  27         HOSTID=$(hostid)
  28         AA=$(echo $HOSTID | cut -b 1,2)
  29         BB=$(echo $HOSTID | cut -b 3,4)
  30         CC=$(echo $HOSTID | cut -b 5,6)
  31         DD=$(echo $HOSTID | cut -b 7,8)
  32
  33         # Big Endian
  34         if echo | gcc -E -dM - | grep -q "__BYTE_ORDER__.*__ORDER_BIG_ENDIAN__"; then
  35                 # Invoke the printf from coreutils. shell builtin lacks the byte format.
  36                 /usr/bin/printf "\x$AA\x$BB\x$CC\x$DD" >/etc/hostid
  37         else
  38         # Little Endian
  39                 /usr/bin/printf "\x$DD\x$CC\x$BB\x$AA" >/etc/hostid
  40         fi
  41 fi
  42
  43 #DEBHELPER#