[Unix-jun72] cold boot tape

Tim Newsham newsham at lava.net
Sat May 3 03:05:49 AEST 2008

> I wrote a utility for building a cold boot tape and included it in the
> tools directory.  Its not yet tested so its possible I got the format
> wrong... its based on my reading of init at the end of u0.s.

It occurs to me that the tape is probably meant to be bootable.
The init program seeks to the 65th block to start booting, so blocks
0 through 64 can be used to hold a bootable kernel image or two.
I'm guessing we could make a tape as:

     blocks 0-31  - the "cold" kernel
     blocks 32-64 - the real kernel
     blocks 65-   - the contents of /bin and /etc

boot the cold kernel from tape, have it write out a primordeal root
file system on rf0.  Boot the real kernel from tape, have it
run the /etc/init that the cold kernel put onto rf0 which reads
files from blocks 65 onwards on the tape.  Finally reboot the real
kernel from tape again and be in a real system.

By the way, I made some tape images from the s2 binaries (just /etc
and /bin, /usr is probably meant to go onto rk0):

        - the raw tape bits with the first 65 blocks empty
        - a simh format tape of the above bits

the tape image isnt tested yet.  It should hopefully have the right
uids and file modes for first ed.

Tim Newsham

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