|Subject:||my simple OS won't boot in QEMU|
|Date:||Fri, 2 Apr 2021 12:15:49 -0700|
|User-agent:||Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1|
This post concerns booting sda2 using QEMU. sda2 boots just fine
when run on HD.
File qemu4dell.img is an image of the first 3 partitions created using the linux dd command as follows:
dd if=/dev/sda of=qemu4dell.img bs=512 count=4082720 (the file
has 6 extra bytes).
In the first sector (the MBR) of qemu4dell.img I have zeroed out line 4 of the partition table because the file does not include partition 4.
If the boot flag is set for sda1 in file qemu4dell.img the command line above boots sda1 (MSDOS 6.22) just fine.
If the boot flag is set for sda2 in file qemu4dell.img the command line above results in error message:
missing operating system.Careful examination of the boot program (IPL) in the first sector of qemu4dell.img shows that that message occurs if the IPL can't find the hex value AA55 at the end of the first sector of the partition to be booted (which is sda2). I refer to the first sector of sda2 as vbs2. I have double checked in qemu4dell.img and ensured that vbs2 sector is in the correct location in the file and that the value AA55 is in the correct place in the sector.
I can see no reason why QEMU doesn't boot sda2, because QEMU can boot sda1 ok, and also sda2 boots fine on the HD itself. Perhaps someone in this QEMU group knows the answer.
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