Documentation/block/blockconsole/bcon_tail

#!/bin/bash

TAIL_LEN=16
TEMPLATE=/tmp/bcon_template
BUF=/tmp/bcon_buf

if [ $(whoami) != "root" ]; then
	echo "You need to be root to run this."
	exit 1
fi

if [ -z "$(which lsscsi)" ]; then
	echo "You need to install the lsscsi package on your distro."
	exit 1
fi

if [ -z "$(which hdparm)" ]; then
	echo "You need to install the hdparm package on your distro."
	exit 1
fi

end_of_log() {
	DEV=$1
	UUID=`head -c40 $DEV|tail -c8`
	LOGFILE=/var/log/bcon.$UUID
	SECTORS=`hdparm -g $DEV|grep sectors|sed 's/.*sectors = \([0-9]*\).*/\1/'`
	#MSIZE=`expr $SECTORS / 2048`
	dd if=$DEV iflag=direct bs=512 2>/dev/null|head -c50 > $TEMPLATE
	#START, MIDDLE and END are in sectors
	START=0
	MIDDLE=$SECTORS
	END=$SECTORS
	while true; do
		MIDDLE=`expr \( \( $END + $START \) / 4096 \) \* 2048`
		if [ $MIDDLE -eq $START ]; then
			break
		fi
		dd if=$DEV iflag=direct bs=512 count=1 skip=$MIDDLE 2>/dev/null|head -c50 > $BUF
		if diff -q $BUF $TEMPLATE > /dev/null; then
			START=$MIDDLE
		else
			END=$MIDDLE
		fi
	done
	#switch to megabytes
	END=`expr $END / 2048`
	START=`expr $START / 2048`
	if [ $START -lt $TAIL_LEN ]; then
		START=0
	else
		START=`expr $START - $TAIL_LEN + 1`
	fi
	LEN=`expr $END - $START`
	dd if=$DEV iflag=direct bs=1M count=$LEN skip=$START >$LOGFILE 2>/dev/null
	echo $LOGFILE
}

# HEADER contains a newline, so the funny quoting is necessary
HEADER='
Linux blockconsole version 1.1'
CANDIDATES=`lsscsi |sed 's|.*/dev|/dev|'`

for DEV in $CANDIDATES; do
	if [ "`head -c32 $DEV`" == "$HEADER" ]; then
		end_of_log $DEV
	fi
done