On Sun, Jan 23, 2022 at 5:44 AM Richard Miller <9f...@hamnavoe.com> wrote: > > !rc (and the rest of the boot) is one of the first things implemented > > uniquely by 9front. > > I think there's a little bit of confusion about different stages of booting. > > The 9boot program loads the kernel. The original Plan 9 9boot is driven > by configuration variables in a plan9.ini file. Cinap's rewritten 9boot > adds the capability of interactively changing configuration variables from > the console before loading the kernel. That's really useful, especially > when experimenting with new kernels or new hardware. But 9boot does not > contain a shell or a built-in file system, so it doesn't allow you to > type !rc and get an interactive shell. > > Once the kernel is loaded, the first thing it does is to execute the > command /boot/boot from a small root filesystem which is built into the > kernel. The main job of /boot/boot is to attach to the real root filesystem > (on a local device or from a network server) and execute /$cputype/init to > start the system. Historically the usual case is for /boot/boot to > be a specialised program built from C source in /sys/src/9/boot. But it > has always been possible to configure a kernel with a shell script as > /boot/boot - see for example /sys/lib/sysconfig/ppc/boot for the PowerPC, > or /sys/src/9/bcm/bootwifi.rc for a Raspberry Pi accessing its root file > server via wifi. > > So, using a shell script as /boot/boot is not unique to 9front. But > with 9front, it has become the default. This means there's always a > shell inside the kernel, along with a few commands, ready to use > interactively when !rc is invoked - after the kernel is loaded, but > before the final root filesystem is attached. > > The kernel on the 9legacy install CD doesn't have a shell script as > /boot/boot with the ability to invoke !rc. Perhaps it should. But that > wouldn't have helped in this case. Yakku was stuck at the 'Boot from' > prompt within /9boot, unable to find a kernel to boot. >
Richard, Thank you for the detailed explanation. I misread the part about no kernel and thought we made it to the boot prompt and could not figure out the disk name. Mea culpa. ------------------------------------------ 9fans: 9fans Permalink: https://9fans.topicbox.com/groups/9fans/Tb5aaf646618a421a-M63efb6f310bdb085365dc15f Delivery options: https://9fans.topicbox.com/groups/9fans/subscription
