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Multibooting and Partitioning Experiments
saikee:
Someone has drawn my attention to this thread,
Wonder what you guys make out of this?
I am in a hurry now but would make a comparison later on.
Recently I have to show someone in another forum about booting up 3 Dos and 5 Windows and explained in Post #70 of this thread.
I have not put MS systems into logical partitions though.
wolf.b:
Hi saikee,
thank you for your links! :Thmbsup:
As it will take me a while to read those threads, I wonder if you could answer a basic question:
Is there a limit on the max number of logical partitions on a single HDD (S-ATA)? I mean, if I have an extended partition with 30,000 cylinders, does that allow 30,000 different logical drives inside? Surely not, but you wrote that the limit of 63 logical drives is not true anymore. I could not find yet the answer, still reading ...
Thanks in advance
Wolf
Edit(1): I guess it is 11?
Edit(2): Would you be kind enough to have a look at Reply#16 of this thread and maybe point me in the right direction to create a GRUB boot floppy. At present I use GRUB4DOS on my active primary partition, but I would appreciate any help.
saikee:
To make a Grub floppy
This is fully described in the Chapter 3.1 of the Grub Manual. It requires you to copy two files; stage1 and stage2 into a floppy. The copying command is "dd" which operates at a hardware level.
Basically you find stage1, specify it as the input, nominate the floppy (fd0) as the output and write out a block of 512 bytes only once.
Then you write stage2, block size 512 byte (exact sector size) starting from the 2nd sector until the file stage2 is exhausted.
You can "source" the two Grub files from most of the Linux Live CD. Any one form the Ubuntu, PCLinux, Knoppix, Fedora, Mepis, etc . The only ones that do not have Grub is the Slax and Slackware families as they use the alternative Linux boot loader Lilo.
You boot up a Linux Live CD, click terminal and and obtain the root privilege by the "sudo su" command (works in most distro like Ubuntu and Knoppix). You then ask Linux to tell you where stage1 is being stored. You then change directory to it, drop a floppy into the drive and copy the two files into the floppy. I am repeating the instruction with an installed Ubuntu below
--- ---sudo su
find / -name stage1
cd /usr/lib/grub/i386-pc
dd if=stage1 of=/dev/fd0 bs=512 count=1
dd if=stage2 of=/dev/fd0 bs=512 seek=1
The full response in the terminal looks like this
--- ---saikee@saikee-desktop:~$ sudo su
Password:
root@saikee-desktop:/home/saikee# find / -name stage1
/boot/grub/stage1
/home/saikee/big_iso/boot/grub/stage1
/home/saikee/big_iso/boot-berry/Setup/stage1
/usr/lib/grub/i386-pc/stage1
root@saikee-desktop:/home/saikee# cd /usr/lib/grub/i386-pc
root@saikee-desktop:/usr/lib/grub/i386-pc# ls
e2fs_stage1_5 jfs_stage1_5 reiserfs_stage1_5 stage2 xfs_stage1_5
fat_stage1_5 minix_stage1_5 stage1 stage2_eltorito
root@saikee-desktop:/usr/lib/grub/i386-pc# dd if=stage1 of=/dev/fd0 bs=512 count=1
1+0 records in
1+0 records out
512 bytes (512 B) copied, 0.278956 seconds, 1.8 kB/s
root@saikee-desktop:/usr/lib/grub/i386-pc# dd if=stage2 of=/dev/fd0 bs=512 seek=1
215+1 records in
215+1 records out
110132 bytes (110 kB) copied, 8.42257 seconds, 13.1 kB/s
In the above there were two sources for stage1. Either one will do.
I also did a "ls" command which is identical to "dir" in Windows command prompt to show all the Grub files.
This Grub floppy can boot any installed operating system that has ever been invented on a PC. I classify it as the most lethal booting weapon in the business.
This thread may be useful if you ever get lost in booting a PC system.
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Linux uses a major and minor numbering system to define block devices and a hard disk of SCSI, Pata, Sata or USB type can have 16 device names. Since one device name must be reserved for the whole of the disk, say sda, and there are 4 primaries that leaves 11 logical partitions possible. In order to use logical partitions, even one, a primary partition must be given up to accommodate all the logical partitions inside.
sda1 to sda4 are reserved for primaries and every logical partition starts at sda5. Linux names disks sda, sdb, sdc, sdd, sde, sdf, ......etc. Before the 2.6.20 kernel changes both Pata and Sata can have a total of 256 devices. Pata achieved it through 4 disks each 64 devices names whereas Sata did the same with 16 disks each has 16 device names. I have reason to believe the 16 hard disks are still supported when the Pata disk has been grouped into the same SCSI/Sata/USB family.
The nice thing about Linux is you are free to do whatever you want as long as you go with the established convention. Thus one can use trick to get 44 logical partitions out of a hard disk. My second hard disk has 44 OSes inside working merrily.
wolf.b:
Hi saikee!
Thanks for your reply. I have found that my initial problems with a GRUB floppy were probably related to buggy BIOS, bad floppy disk, old hardware or some such. The floppy I have created following your walkthrough in the reply#37 works perfectly :) on only one of my laptops, but not on my desktop or inside a VM on that desktop. :( I have found another way here to create a GRUB floppy on a FAT formatted floppy (uses mkfs -t msdos /dev/fd0). That one, funny enough, is the other way round, works on my desktop and inside VM, but not on my laptop. Anyway, I now think that my first attempts were not all that bad, I might have tested that first floppy on the wrong machine. So thanks again for encouraging me to give it another go.
Have you ever tested GRUB4DOS?
What do you think of the possibilities to load disk images into RAM?
Is there a reward for beating your record of getting 44 different bootable Linux distros (or 44 logical drives) onto a single S-ATA disk? Just kidding. Would I be allowed to use workarounds (non-grub methods) to achieve that?
Greetings
Wolf
saikee:
I have Grub4Dos inside some Dos partitions. Since I can load Grub virtually from anywhere the use of Grub4Dos is diminishing. It does have other bits and pieces but I haven't put all of them to use yet.
Many applications are just loading a disk images into ram. Just about every Linux Live CD has to do exactly that.
I don't own the PC standard but just use it like everybody else. If there is a way to get more partitions out in the normal way then I would love to know. One can purchase a partitioning management layer software to get 256 primaries apparently but it is not recognised by established systems. LVM is not universally supported otherwise one can place an OS in every logical volume.
44 paritions suit users with large hard disks like 500Gb as every operating system can be comfortably fitted into a 25Gb space.
I never format a Grub floppy and rarely have a problem with anyone I made. The dd command should destroy the floppy's partition table and so the end product should be identical. This means the floppy should be reported as unformatted and there is no file inside because dd write the code directly onto the floppy sectors.
If you know dd you should know it can be used to clone any XP and Vista.
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