preinst is in psad 2.2.3-1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82  | #!/bin/sh
#
# Update_conf
#
# This function searchs a key entry in a file and updates its value with the new
# one.
#
# Syntax:
#
#    update_conf new_val key conffile
#      -> new_val ... : Value to set for the key value
#      -> key ....... : Name of the key to be updated
#      -> conffile .. : File to search
#
update_conf ()
{
        local new_val
        local key
        local conffile
        new_val=$1
        key=$2
        conffile=$3
        cp $conffile $conffile.old
        old_val=`awk '$1 == "'$key'" { print $2 }' $conffile`
        awk '$1 == "'$key'" { gsub("'$old_val'","'$new_val';",$0); \
                           print $0 } \
                 $1 != "'$key'" { print $0 }' \
                 $conffile.old > $conffile
        rm $conffile.old
}
if [ "$1" = "upgrade" -o "$1" = "install" ]; then
    # Revert changes added to the configuration file by the postinst script
    # if we are upgrading from a version which changed it (#688891)
    # or if we are installed with a prior version (#675231)
    if [ -n "$2" ] && dpkg --compare-versions 2.2-3 gt $2 ; then
        update_conf "_CHANGEME_" "HOSTNAME" "/etc/psad/psad.conf"
    fi
fi
if [ "$1" = "upgrade" ]; then
    # This script is only intended to fix bug #497574.
    # We check for an upgrade from Psad older than 2.1.5 and remove the old
    # Psad process if needed.
    #
    # NB: As some commands can return an exit code other than 0 we do not use
    # *set -e* at the beginning.
    status=1;
    if [ -x "`which dpkg 2>/dev/null`" ]; then 
        dpkg --compare-versions 2.1.5 gt $2
        status=$?
    fi
    if [ $status = 0 ]; then
        echo -n "Removing old Psad process ... "
        process_list="psadwatchd kmsgsd psad"
        for process in $process_list; do
	    pkill $process 2>/dev/null
        done
        echo "Done."
    fi
fi
set -e
exit 0
 |