Usage of the free BIOS PMON2000
A very good on-line manual is the Yeeloong PMON Full User Guide.
The original manual can be downloaded in the official web site (in Chinese). If you know where is an english version, add here a link (which works) to it.
Entering to the command line
After powering the computer on (while watching the image with the chinese letters), keep DEL key ('c' key in the boot menu) pressed until you got it.
Showing the content of a device
For example, for seeing the first partition of the first hard disk
- dir (wd0,0)
Also, it can show subdirectories
- dir (wd0,0)/boot
How to boot an installed distro manually
First, load the kernel (you must know where it is located, use 'dir' as above for looking for it if necessary). For example
- load (wd0,2)/boot/vmlinux
Then, boot the system. You must specify where is the file system in 'root' parameter
- g console=tty no_auto_cmd root=/dev/sda3
(Notice the difference between the (wd0,x) and the /dev/sday notation)
The package for installing GRUB2 (it happened me in gNS/Debian) will have the only name grub-yeeloong instead of grub2, which normally redirects to the correct version that you would need.
boot.cfg is the main boot configuration file and is one of the first things that BIOS checks. It says which kernel to load or, usually. it redirects you to another menu created by grub2. You can read the PMON Start-up Flow where is explained the edition of boot.cfg.
It seems that the only way to change where pmon looks for the boot.cfg is to recompile pmon. By default, it is searched in the first partion (wd0,0). Because of that, if you use a bootloader you'll probably want to have a distro which you use frequently in the fist partition, since you'll have to do 'update-grub2' from there for changes take effect.
Avoiding the use of a bootloader
It is not necessary to install grub for booting a installed operating system. You can just set the al PMON variable with the path to the kernel, as described in the PMON manual. Be careful of set the different variables correctly, and remember that PMON cannot read ext4 filesystems, so the best solution is to have a separate partition for /boot formated with ext2 or ext3.
Warning: I have to press ENTER after a few seconds (~6). Without that, the kernel doesn't start the loading process.