Here is a shell-script that will demonstrate the problem with the
loop device as previously reported.
The first time you execute this script, it will (may) execute without
any errors. The next time, all bets are off. It will even reset your
CMOS clock (honest). This is chopped out of a script that I used to make
a bootable NVRAM system.
#!/bin/sh
#
export VER=1234
RAMDISK_IMAGE=/tmp/RamImage-${VER}
RAMDISK=/tmp/Ramdisk
TMPC=/tmp/Temp.c
TMPF=/tmp/TmpExe
DISKSIZE=4096
#
umount ${RAMDISK} 2>/dev/null
mkdir ${RAMDISK} 2>/dev/null
dd if=/dev/zero of=${RAMDISK_IMAGE} bs=1k count=${DISKSIZE}
/sbin/mke2fs -Fq ${RAMDISK_IMAGE} ${DISKSIZE}
mount -o loop -t ext2 ${RAMDISK_IMAGE} ${RAMDISK}
rmdir ${RAMDISK}/lost+found
#
# Make the required directories in the RAM Disk.
#
mkdir -m 777 ${RAMDISK}/dev
mkdir -m 777 ${RAMDISK}/etc
mkdir -m 777 ${RAMDISK}/lib
mkdir -m 777 ${RAMDISK}/usr
mkdir -m 777 ${RAMDISK}/usr/local
mkdir -m 777 ${RAMDISK}/bin
mkdir -m 777 ${RAMDISK}/sbin
mkdir -m 777 ${RAMDISK}/tmp
mkdir -m 777 ${RAMDISK}/proc
#
# Make the required devices.
#
mknod ${RAMDISK}/dev/null c 1 3
mknod ${RAMDISK}/dev/ram0 b 1 0
mknod ${RAMDISK}/dev/ram1 b 1 1
mknod ${RAMDISK}/dev/mem c 1 1
mknod ${RAMDISK}/dev/ttyS0 c 4 64
mknod ${RAMDISK}/dev/tty0 c 4 0
mknod ${RAMDISK}/dev/tty1 c 4 1
mknod ${RAMDISK}/dev/tty2 c 4 2
mknod ${RAMDISK}/dev/tty3 c 4 3
mknod ${RAMDISK}/dev/tty4 c 4 4
mknod ${RAMDISK}/dev/tty c 5 0
mknod ${RAMDISK}/dev/ttyp0 c 3 0
mknod ${RAMDISK}/dev/ttyp1 c 3 1
mknod ${RAMDISK}/dev/ttyp2 c 3 2
mknod ${RAMDISK}/dev/ttyp3 c 3 3
mknod ${RAMDISK}/dev/ttyp4 c 3 4
mknod ${RAMDISK}/dev/ttyp5 c 3 5
mknod ${RAMDISK}/dev/ptyp0 c 2 0
mknod ${RAMDISK}/dev/ptyp1 c 2 1
mknod ${RAMDISK}/dev/ptyp2 c 2 2
mknod ${RAMDISK}/dev/ptyp3 c 2 3
mknod ${RAMDISK}/dev/ptyp4 c 2 4
mknod ${RAMDISK}/dev/ptyp5 c 2 5
mknod ${RAMDISK}/dev/zero c 1 5
mknod ${RAMDISK}/dev/GPIB c 125 0
mknod ${RAMDISK}/dev/NVRAM c 126 0
mknod ${RAMDISK}/dev/platinum c 127 0
#
df ${RAMDISK}
umount ${RAMDISK}
rmdir ${RAMDISK}
rm ${RAMDISK_IMAGE}
It looks like the first time you access the loop device, it writes
okay. However, later writes have no effect. It's interesting that
removing the module, then reinstalling it has no effect. The data,
once on the device, stays there!
Cheers,
Dick Johnson
Penguin : Linux version 2.3.36 on an i686 machine (400.59 BogoMips).
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Jan 07 2000 - 21:00:09 EST