On Wed, 9 Dec 2009 08:45:20 Marc Chamberlin wrote:
Well I am totally confused about using YaST2 to setup the bootloader, and no amount of reading documentation or searching the internet has allowed me to grok the underlying model of how this works... I am not looking for a cookbook set of instructions (which I find all over the place) BUT some clarification of terminology and what really is going on when I select various options.
I have a system with multiple versions of SuSE installed on various different disk drives. I am using GRUB. In the YaST module for setting up the boot loader, there is a panel titled Boot Loader Installation and within that panel I am allowed to choose between one (or more) boot loader locations and this is where I am confused. The Help menu does not help either, just makes things even more confusing!
Marc, First, can I politely suggest some reading that may help you understand what happens during the boot process? That understanding will help you figure out the answers to your questions below: http://www.ibm.com/developerworks/linux/library/l-linuxboot/ http://docs.fedoraproject.org/install-guide/f12/en-US/html/ch-boot-init- shutdown.html http://docs.fedoraproject.org/install-guide/f12/en-US/html/ch-grub.html The last 2 are from the Fedora project but give a good insight into the terminology and should answer more of your questions.
So here are my questions -
1. The first choice offers me the option to Boot from Boot Partition. I cannot find a definition of what a "Boot Partition" is exactly, but my guess is that this is a partition that I will set fstab up to mount as /boot Is that correct?
Yes. Traditionally in Unix systems /boot lived on a dedicated partition. On Linux this partition contains only the kernal images, kernel config files and stage 2 boot loader.
If so, (and I would argue that this is a bad way to name and describe it) why would I want to create a partition just for /boot? What would be the advantage and disadvantage of doing so.
That is how it is traditionally done and there are some valid reasons for doing so, however many current distributions don't do this by default.
It seems to me that in an environment with multiple operating systems or versions of the same OS, that this might be a incredibly dangerous thing to do.. If a later version of an OS or GRUB is installed and wants to change, add, delete or modify files or the structure of files within this area, then that could break other or earlier versions of an OS, which is also dependent upon a common boot partition. Or is the thinking behind this option, to have each OS have its own boot partition? Is so why would that be an advantage?
No, just the opposite. The boot loader is told which partitions to load from. No other partitions are mounted at this time. Once control is passed to the kernel then other partitions are mounted (which is when the boot partition becomes visible as /boot). Separate boot partitions for each OS (where only the relevant one is mounted by the running system) prevents having the others overwritten accidentally.
2. The second choice is Boot from Extended Partition. I can find very little documentation on this feature and it somewhat baffles me. I am again guessing that this has something to do with installing an OS in an extended partition, but why should I have to explicitly specify that I am doing so? What is different about this option, that is not covered when either Boot From Boot Partition or Boot From Root Partition is chosen? If the Boot Partition or the Root Partition is in an extended partition why can't YaST simply figure that out and do what ever is necessary to support it? Or perhaps (and just a wild guess) does this have more to do with loading the OS from and extended partition and nothing to do with where the bootloader code actually exists? What does booting from an Extended Partition REALLY mean?
The grub configuration file refers only to physical partitions, not mounted filesystems. I'm not sure exactly of the configuration differences between booting from a primary partition or booting from an extended partition (which, remember, is a virtual partition with a partition number above 5).
3. The third choice is Boot from Master Boot Record. While I think I understand the basic idea of the Master Boot Record, a couple of questions regarding it have come to my mind. First, the Help menu states that if one is going to have multiple OS's on ones system, then this method should not be used (not recommended) Well.... I have been using this method, and it seems to work OK. I use this method only because that apparently is the default method chosen by the SuSE installation process. This poor user would assume that if the installation process has the ability to detect if multiple operating systems are already installed, then the installation process would be smart enough to decide whether a boot from a MBR would be acceptable or not... So why is this not the recommended method for systems with multiple OS's?
Other OS's have their own boot loaders. If you install the other OS after installing grub/linux, the MBR will be overwritten, thus rendering your Linux system non-bootable. To overcome this, you need to install Linux/grub last. Grub then installs Stage 1 in the MBR and can chain-load the other OS bootloaders. The reading contained in the links I posted above will make this much clearer. If you choose to install grub to the MBR, it will install Stage1 and Stage 1.5 in the MBR; stage 2 will always reside in /boot/grub, regardless of whether /boot is a separate partition or not. HTH, Rodney. -- =================================================== Rodney Baker VK5ZTV rodney.baker@iinet.net.au =================================================== -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org