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|
#!/bin/bash
#
# rassplit and rasmerge: An example of using ras(1) to split a large
# file across multiple floppies with redundancy.
#
# rassplit usage: rassplit <number> <file>
# Split <file> onto floppies, including enough redundancy that <file>
# can still be regenerated if up to <number> floppies fail.
#
# The mount-point for the floppy drive
FLOPPY=/floppy
# The command used to mount the floppy
MOUNT="mount $FLOPPY"
# The unmount command
UMOUNT="umount $FLOPPY"
# The size of the chunks into which <file> is to be split. Should be a bit
# less than the capacity of the floppies.
SEGSIZE=1400000
############################################################################
function file_to_floppy ()
# Copy the file $1 to the floppy drive, prefixed by a pre-calculated md5
# checksum that's been saved in a file $1.md5. Overwrite the current
# contents of the floppy.
{
echo "Putting file $1, insert formated floppy and press RETURN"
printf '\a'
read -e
$MOUNT
rm -rf $FLOPPY/*
# Wait for the md5 checksum to appear (it will be calculated by a
# background task that may not have done it yet)
until [ -r $1.md5 ]
do
echo "Waiting for $1.md5 ..."
sleep 1
done
cat $1.md5 $1 >$FLOPPY/$1
$UMOUNT
}
############################################################################
function sumnames ()
# Convert a decimal number from 0 to 10 to a string holding the names to be
# used for ras sumfiles, and put that string in the variable SUMNAMES. For
# example, "sumnames 3" will put "sum0 sum1 sum2" in SUMNAMES.
{
case "$1" in
0) NUMS="" ;;
1) NUMS="0" ;;
2) NUMS="01" ;;
3) NUMS="012" ;;
4) NUMS="0123" ;;
5) NUMS="01234" ;;
6) NUMS="012345" ;;
7) NUMS="0123456" ;;
8) NUMS="01234567" ;;
9) NUMS="012345678" ;;
10) NUMS="0123456789" ;;
*) echo "Invalid arg to sumnames: $1"
exit 1
;;
esac
SUMNAMES=`echo $NUMS | sed -e 's/\(.\)/sum\1 /g' -e 's/ $//'`
}
############################################################################
FILE="$2"
if [ ! -r $FILE ]
then
echo "rassplit: Cannot read from file $FILE"
exit 1
fi
SUMCOUNT="$1"
sumnames "$1"
#
# Split a tar file of the file specified and an md5 sum of it into a
# temporary directory.
#
TMP="/tmp/rassplit.$$"
rm -rf $TMP
mkdir $TMP
md5sum "$FILE" >ras.md5sum
tar cvf - "$FILE" ras.md5sum | (cd $TMP ; split -b 1400000)
rm ras.md5sum
cd $TMP
#
# Determine how many, if any, sumfiles need to be generated
#
if [ -r xab ]
then
ONESEG=No # there are at least 2 segfiles
else
ONESEG=Yes # there is only 1 segfile
fi
if [ "$SUMCOUNT" != "0" -a "$ONESEG" == "No" ]
then
SUMFILES="$SUMNAMES" # We wish to generate some ras sumfiles
else
SUMFILES="" # We don't want any sumfiles.
fi
#
# Launch a background job to calculate md5 checksums of the segfiles,
# and then generate (and calculate checksums of) ras sumfiles if any
# are required.
#
(
for i in x??
do
md5sum <$i | sed 's/ .*//' > $i.md5.tmp
mv $i.md5.tmp $i.md5
done
if [ ! -z "$SUMFILES" ]
then
# We want to generate some ras sumfiles, which will also need
# checksums.
ras -cs $SUMFILES
for i in $SUMFILES
do
md5sum <$i | sed 's/ .*//' > $i.md5.tmp
mv $i.md5.tmp $i.md5
done
fi
) &
#
# Copy the files to floppies
#
if [ "$SUMCOUNT" != "0" -a "$ONESEG" == "Yes" ]
then
# redundancy required and only one segment present, get the redundancy
# by having multiple copies of the segment.
for dummy in the_segment $SUMNAMES
do
file_to_floppy xaa
done
else
for file in x?? $SUMFILES
do
file_to_floppy $file
done
fi
#
# Done, tidy up
#
cd / # abandon doomed dir
rm -rf $TMP
|
