Loop back device11/17/2023 That leaves us with a nice sized file full of zeros that we'll use for our disk image. Since we have set bs to 516096 bytes each block is one cylinder long Means read and write 516096 bytes at a time (This is just here to keep things simple)Ĭopy this number of blocks. Source file is /dev/zero which is.*drumroll*.an infinite source of zerosĭestination file is our disk image (dd will create the file if it doesn't exist) Linux command for copy and convert a file Write the disk image (I'll assume the filename c.img throughout):ĭd if=/dev/zero of=/path/to/c.img bs=516096c count=#cylinders Decide how large you want your disk image to be, and choose an appropriate number of cylinders (I’ll be using #cylinders throughout).Įxample: If I want a 500Mb disk, I would choose 1000 cylinders (approximation of (500*1000*1024)/516096). ![]() ![]() We will assume a disk geometry of #cylinders, 16 heads, 63 sectors/track, 512 bytes/sector, which means that each cylinder contains 516096 bytes (16*63*512). To mount a partition contained in our disk image, we need to make sure the 'mount' command only sees our partition, not the whole disk.įirst create the empty file that we will use for our disk image. Mount /dev/loop0 /mnt -t msdos -o "fat=12"Ī hard disk image contains an MBR, then a number of partitions, but the 'mount' instruction in Linux works with disk partitions, not full disks. The steps mentioned below will be useful for the BrokenThorn Entertainment tutorials NOTE: When deleting the loop device, the original floppy.img file will be saved with the modified contents. NOTE: You must unmount /mnt/myfloppy before using a emulator to directly read /dev/loop0, such as: Grub -device-map=/mnt/myfloppy/grub/device.map /dev/loop0 Start GRUB console for installation into the boot record. echo "(fd0) /dev/loop0" > /mnt/myfloppy/grub/device.map You need quotations around the first part. (GRUB stage could also be located in /usr/lib/grub/)Ĭp /lib/grub/i386-pc/stage /mnt/myfloppy/grubĬreate a device mapping for the GRUB installation. The linux loopback device can be used by root only, and needs to be enabled in the kernel before use.ĭd if=/dev/zero of=floppy.img bs=512 count=2880Ĭopy GRUB's second stage files.
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