Two OS
- Thread starter Crusader
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DOS/Windows
GRUB cannot boot DOS or Windows directly, so you must chain-load them (see Chain-loading). However, their boot loaders have some critical deficiencies, so it may not work to just chain-load them. To overcome the problems, GRUB provides you with two helper functions.
If you have installed DOS (or Windows) on a non-first hard disk, you have to use the disk swapping technique, because that OS cannot boot from any disks but the first one. The workaround used in GRUB is the command map (see map), like this:
grub> map (hd0) (hd1)
grub> map (hd1) (hd0)
This performs a virtual swap between your first and second hard drive.
Caution: This is effective only if DOS (or Windows) uses BIOS to access the swapped disks. If that OS uses a special driver for the disks, this probably won't work.
Another problem arises if you installed more than one set of DOS/Windows onto one disk, because they could be confused if there are more than one primary partitions for DOS/Windows. Certainly you should avoid doing this, but there is a solution if you do want to do so. Use the partition hiding/unhiding technique.
If GRUB hides a DOS (or Windows) partition (see hide), DOS (or Windows) will ignore the partition. If GRUB unhides a DOS (or Windows) partition (see unhide), DOS (or Windows) will detect the partition. Thus, if you have installed DOS (or Windows) on the first and the second partition of the first hard disk, and you want to boot the copy on the first partition, do the following:
grub> unhide (hd0,0)
grub> hide (hd0,1)
grub> rootnoverify (hd0,0)
grub> chainloader +1
grub> makeactive
grub> boot
Load another boot loader to boot unsupported operating systems
If you want to boot an unsupported operating system (e.g. Windows 95), chain-load a boot loader for the operating system. Normally, the boot loader is embedded in the boot sector of the partition on which the operating system is installed.
Set GRUB's root device to the partition by the command rootnoverify (see rootnoverify):
grub> rootnoverify (hd0,0)
Set the active flag in the partition using the command makeactive1 (see makeactive):
grub> makeactive
Load the boot loader with the command chainloader (see chainloader):
grub> chainloader +1
+1 indicates that GRUB should read one sector from the start of the partition. The complete description about this syntax can be found in Block list syntax.
Run the command boot
GRUB cannot boot DOS or Windows directly, so you must chain-load them (see Chain-loading). However, their boot loaders have some critical deficiencies, so it may not work to just chain-load them. To overcome the problems, GRUB provides you with two helper functions.
If you have installed DOS (or Windows) on a non-first hard disk, you have to use the disk swapping technique, because that OS cannot boot from any disks but the first one. The workaround used in GRUB is the command map (see map), like this:
grub> map (hd0) (hd1)
grub> map (hd1) (hd0)
This performs a virtual swap between your first and second hard drive.
Caution: This is effective only if DOS (or Windows) uses BIOS to access the swapped disks. If that OS uses a special driver for the disks, this probably won't work.
Another problem arises if you installed more than one set of DOS/Windows onto one disk, because they could be confused if there are more than one primary partitions for DOS/Windows. Certainly you should avoid doing this, but there is a solution if you do want to do so. Use the partition hiding/unhiding technique.
If GRUB hides a DOS (or Windows) partition (see hide), DOS (or Windows) will ignore the partition. If GRUB unhides a DOS (or Windows) partition (see unhide), DOS (or Windows) will detect the partition. Thus, if you have installed DOS (or Windows) on the first and the second partition of the first hard disk, and you want to boot the copy on the first partition, do the following:
grub> unhide (hd0,0)
grub> hide (hd0,1)
grub> rootnoverify (hd0,0)
grub> chainloader +1
grub> makeactive
grub> boot
Load another boot loader to boot unsupported operating systems
If you want to boot an unsupported operating system (e.g. Windows 95), chain-load a boot loader for the operating system. Normally, the boot loader is embedded in the boot sector of the partition on which the operating system is installed.
Set GRUB's root device to the partition by the command rootnoverify (see rootnoverify):
grub> rootnoverify (hd0,0)
Set the active flag in the partition using the command makeactive1 (see makeactive):
grub> makeactive
Load the boot loader with the command chainloader (see chainloader):
grub> chainloader +1
+1 indicates that GRUB should read one sector from the start of the partition. The complete description about this syntax can be found in Block list syntax.
Run the command boot
Yeah I never had problems with GRUB using windows on my old system but this new system will not work I suspect because I loaded Linux onto a older IDE drive I added in and have my windows partitions on a SATA drive. Either way with some tweaking I'll get it to work.
baronvongogo
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GRUB was fine with me, until one day it wouldnt bring up the boot menu. I couldnt fixmbr or fixboot or anything else. So I had to reformat So since then iv gone completly off grub.
baronvongogo
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I dont use anything now Gave up on having linux since that experience. I do have a live cd so can use that.
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