debian/spl.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 # Detect if /etc/hostid is a conffile of previous spl package, migrate if yes
  25 # hostid file should preserve even when package is purged
  26 if $(dpkg-query --showformat='${Conffiles}\n' --show spl >/dev/null 2>&1); then
  27         dpkg-maintscript-helper rm_conffile /etc/hostid -- "$@"
  28 fi
  29
  30 if [ ! -f /etc/hostid ] || [ $(stat -c %s /etc/hostid) -lt 4 ] ; then
  31
  32         # Write our current hostid to /etc/hostid
  33         HOSTID=$(hostid)
  34         AA=$(echo $HOSTID | cut -b 1,2)
  35         BB=$(echo $HOSTID | cut -b 3,4)
  36         CC=$(echo $HOSTID | cut -b 5,6)
  37         DD=$(echo $HOSTID | cut -b 7,8)
  38
  39         # Big Endian
  40         if [ $(echo -n I | od -to2 | awk 'FNR==1{ print substr($2,6,1)}' 2>/dev/null) = 0 ]; then
  41                 # Invoke the printf from coreutils. shell builtin lacks the byte format.
  42                 /usr/bin/printf "\x$AA\x$BB\x$CC\x$DD" >/etc/hostid
  43         else
  44         # Little Endian
  45                 /usr/bin/printf "\x$DD\x$CC\x$BB\x$AA" >/etc/hostid
  46         fi
  47 fi
  48
  49 #DEBHELPER#