Date: Wed, 09 Jun 2010 17:28:47 -0700 From: "Jason C. Wells" <jcw@speakeasy.net> To: freebsd general questions <freebsd-questions@freebsd.org> Subject: Re: Configure PMBR to Find Loader on GPT Disk Message-ID: <4C1031BF.3020703@speakeasy.net> In-Reply-To: <4C0F06B4.9070300@speakeasy.net> References: <4C0F06B4.9070300@speakeasy.net>
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Jason C. Wells wrote: > After setting up a GPT disk and installing the boot blocks with: > > # gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 ad4 > > The system wants to boot: > > 0:ad(0p2)/boot/kernel/kernel > > I manually intervene to cause the system to boot: > > 1:ad(5p8)/boot/loader > > How do I configure the boot blocks to do this without human > intervention on a GPT system? boot0cfg doesn't seem to be the correct > tool for this job. The docs and various guides around the net could use a little help. Please correct me below. My C and assembly is non-existent and I discovered the information below by trial and error and reading the source. My subject header is wrong. The pmbr is working just like it should. It is gptboot that is failing to find my boot loader. I found a work around for the non-configurability of the pmbr/gptboot code. gptboot searchs for the first UFS partition and tries to use that partition as root. In my partition scheme, the first partition was for user data. The presence of boot.config in the first partition will cause gptboot to boot some other disk and partition of your choice. In my case, I added 1:ad(5p8)/boot/loader to boot.config on 0:ad(4p2) to allow my system to boot automatically. Also, some guides online magically select the size of 64k for the freebsd-boot partition. This is not just magic. It's mandatory. The pmbr boot code assume that the partition is not larger than 64k and complains if it is larger. Ref my earlier message on that topic. The bad part about all of this is that I intend to build a mirror from two disks. Will my boot process be brittle because the boot.config is not actually located in / where it truly belongs? If I pull bios disk 0, then when I boot, bios disk 1 will be renumbered to bios disk 0. The boot.config file won't be there. The system will fail to boot. It sure would be nice if 'gpart bootcode' would accept '1:ad(5p8)/boot/loader' as an option so I don't have to be sticking boot.config files in weird locations. Regards, Jason A partition of type freebsd-boot is NOT where you mount /boot.
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