Linux 和 Windows 共享交换区

1. 前言
现在,越来越多的人在一台使用Linux 和 Windows. 这应该说是Linux的胜利. 我们知
道, Linux 要使用交换分区，
Windows 要使用交换文件。如果一台PIII, 有192M 内存，我们分配给Linux 192M 交换
区， Windows 2000 至少要
200M. 那么，我们要用近400M硬盘空间。如果交换区更大，浪费就更可观了。
由于两个系统的交换区都只是运行时的临时数据,所以,我们采用动态修改分区信息的方法
来达到共享目的.

2. 方法简介
1). 备份Windows 分区信息。
2). 当启动Linux时， 将该分区做成Linux 交换区，并将其激活。
3） 当Linux 关闭时，将该分区重新变成Windows 交换区。

3. 具体步骤
1). 分区
Fdisk, 只分主分区, 不分扩展分区
2). 安装 Windows.
3). 安装Linux (占一个主分区)
4). 在Linux 下, 分扩展分区)
5). 设定Linux交换区(假定/dev/hda10)
6). 建立winswap 设备
ln -s /dev/hda10 /dev/winswap
7). 启动Linux, 关闭交换区
# swapoff -a
8). 从文件安装表中删除该分区
vi /etc/fstab
注释掉该行 (/dev/hda10)
9). 将该分区该成 FAT16 或其他 DOS 分区.
10). 启动 Windows
a). 格式化该分区
b). 将系统的交换文件设在该分区.
11). 启动 Linux, 计算Total Special Sectors
公式:
T = r + (s * f) + (d / 16)
参数:
Reserved Sectors at beginning : r
FAT Copies : f
Sectors per FAT : s
Root directory entries : d
参见: msinfo.sh
注解: 可以运行 msinfo.sh 来获得.
# msinfo.sh /dev/hda10

12). 备份Windows 分区信息
# dd if=/dev/winswap bs=512 count=XXX | gzip -9 > /etc/winswap.gz
这里, XXX = T
14). 编写启动, 退出脚本, 并把它们放在 /etc/rc.d/xxx.
可用 grep -nr * | grep swapon (或 swapoff) 来找系统激活和关闭交换区, 将它们
替换称我们
的脚本)
我们在附录中提供了启动和关闭的脚本.
4. 附加说明
1. 本文使用的是FAT16, 如果使用NTFS 或其它, 必须修改脚本.
2. mkswap /dev/winswap 377496 (这个值需要修改, 依照你的分区大小)

5. 参考资料:
Linux HOWTO: Swap-space

6. 附录 -- 相应的脚本
1. msinfo.sh 脚本
#!/bin/sh
#
# msinfo.sh This shell script displays the boot sector of the
# given partition.
#
# Author: Rahul U. Joshi
#
# Modifications Removed the use of expr and replaced it by the let
# command.

# check for command line arguments
if [ $# -ne 1 ]; then
echo "Usage: msinfo "
exit 1
fi

# check whether the input name is a block device
if [ ! -b $1 ]; then
echo "msinfo: $1 is not a block device"
exit 1
fi

# create two temporary files for use
TMPFILE=`mktemp -q /tmp/$0.XXXXXX`
if [ $? -ne 0 ]; then
echo "msinfo: Can't create temp file, exiting..."
exit 1
fi

TXTFILE=`mktemp -q /tmp/$0.XXXXXX`
if [ $? -ne 0 ]; then
echo "msinfo: Can't create temp file, exiting..."
rm -f $TMPFILE
exit 1
fi

back_title="`printf "%78s" "msinfo, Information about FAT16 filesystem --
Rahul
Joshi"`"

dialog --title "Boot sector of $1" --backtitle "$back_title" --infobox
"nAnalysing boot sector for $1nPlease wait ..." 14 60

# truncate TXTFILE to zero length
echo > $TXTFILE

# get Formatting DOS version
dd 2>/dev/null if=$1 bs=1 count=8 skip=3 | dd 2>/dev/null of=$TMPFILE
printf >>$TXTFILE "%30s : %sn" "Formatting DOS version" "`cat $TMPFILE`"

# get file system
dd 2>/dev/null if=$1 bs=1 count=8 skip=54 | dd 2>/dev/null of=$TMPFILE
printf >>$TXTFILE "%30s : %sn" "Filesystem" "`cat $TMPFILE`"

# check if filesystem in a FAT16
if [ "`cat $TMPFILE`" != "FAT16 " ]; then
dialog --title "Boot sector of $1" --backtitle "$back_title" --infobox
"nCan't find a FAT16 filesystem on $1" 14 60
exit 2
fi

# get volume label in boot sector
dd 2>/dev/null if=$1 bs=1 count=11 skip=43 | dd 2>/dev/null of=$TMPFILE
printf >>$TXTFILE "%30s : %sn" "Volume label in boot sector" "`cat
$TMPFILE`"

# get Sector size
dd 2>/dev/null if=$1 bs=1 count=2 skip=11| od -An -tdS | dd 2>/dev/null
of=$TMPFILE
printf >>$TXTFILE "%30s : %dn" "Sector size" `cat $TMPFILE`
sector_size=`cat $TMPFILE`

# get Reserved sectors
dd 2>/dev/null if=$1 bs=1 count=2 skip=14| od -An -tdS | dd 2>/dev/null
of=$TMPFILE
printf >>$TXTFILE "%30s : %dn" " Reserved sectors" `cat $TMPFILE`
reserved_sectors=`cat $TMPFILE`

# get FAT sectors
dd 2>/dev/null if=$1 bs=1 count=1 skip=16| od -An -tdS | dd 2>/dev/null
of=$TMPFILE
fat_count=`cat $TMPFILE`

dd 2>/dev/null if=$1 bs=1 count=2 skip=22| od -An -tdS | dd 2>/dev/null
of=$TMPFILE
sectors_per_fat=`cat $TMPFILE`

# calculate the no of sectors allocated for FAT's
let fat_sectors=fat_count*sectors_per_fat

printf >>$TXTFILE "%30s : %u (%u x %u) n" "FAT sectors" "$fat_sectors"
"$fat_count" "$sectors_per_fat"

# get root directory sectors
dd 2>/dev/null if=$1 bs=1 count=2 skip=17| od -An -tdS | dd 2>/dev/null
of=$TMPFILE
root_sectors=`cat $TMPFILE`

# calculate the no of sectors allocated for root directory
let root_sectors=root_sectors*32/sector_size

printf >>$TXTFILE "%30s : %un" "Root directory sectors" "$root_sectors"

# get Total special sectors
let total=reserved_sectors+fat_sectors+root_sectors
printf >>$TXTFILE "%30s : %un" "Total special sectors" "$total"

# display the information in a message box
dialog --title "Boot sector of $1" --backtitle "$back_title" --msgbox
"`cat $TXTFILE`" 14 60

# delete temporary files
rm -f $TMPFILE
rm -f $TXTFILE

# end of msinfo.sh

2. swapinit.sh
#!/bin/sh
#
# /etc/rc.d/init.d/swapinit.sh - activate the swap partition
#
# written by Rahul U. Joshi
# Verify and initialize swap space
#

echo -n 'Verifying swap space... '

loopcount=0

# flag to indicate whether the partition has been activated or not
activated=0

# check for signatures 6 times before giving up
while [ $loopcount -lt 6 ]
do
if [ "`/bin/dd 2>/dev/null if=/dev/winswap bs=1 count=10 skip=4086`" =
'SWAPSPACE2' ]; then

echo "Linux signature found, iteration $loopcount"
echo "Activating swap partitions"
swapon /dev/winswap
activated=1
break

elif [ "`/bin/dd 2>/dev/null if=/dev/winswap bs=1 count=5 skip=54`" =
'FAT16' ]; then
echo "DOS signature found, iteration $loopcount"
echo "Making swap partition"
mkswap /dev/winswap 377496
echo "Activating swap partitions"
swapon /dev/winswap
activated=1
break

else
let loopcount=loopcount+1
fi

done

if [ $activated -ne 1 ] ; then
echo "Swap signature not found after $loopcount tries"
echo "No swapping partitions activated"
exit 1
fi

3. swaphalt.sh
#!/bin/sh
#
# /etc/rc.d/init.d/swapinit.sh - activate the swap partition
#
# written by Rahul U. Joshi
# Verify and initialize swap space
#

echo -n 'Verifying swap space... '

loopcount=0

# flag to indicate whether the partition has been activated or not
activated=0

# check for signatures 6 times before giving up
while [ $loopcount -lt 6 ]
do
if [ "`/bin/dd 2>/dev/null if=/dev/winswap bs=1 count=10 skip=4086`" =
'SWAPSPACE2' ]; then

echo "Linux signature found, iteration $loopcount"
echo "Activating swap partitions"
swapon /dev/winswap
activated=1
break

elif [ "`/bin/dd 2>/dev/null if=/dev/winswap bs=1 count=5 skip=54`" =
'FAT16' ]; then
echo "DOS signature found, iteration $loopcount"
echo "Making swap partition"
mkswap /dev/winswap 377496
echo "Activating swap partitions"
swapon /dev/winswap
activated=1
break

else
let loopcount=loopcount+1
fi

done

if [ $activated -ne 1 ] ; then
echo "Swap signature not found after $loopcount tries"
echo "No swapping partitions activated"
exit 1
fi
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