Early boot
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NOTE: The contents of this page are not set in stone, and are subject to change! This page is a draft in active flux ... |
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Draft of early boot upgrade/init procedures designed by Michael Stone and C. Scott Ananian.
Early userland startup steps
[initrd] v python2.5 (pid 1) v network_setup(), mount usb/sd, etc v antitheft client (ATC) olpc.atc.run(fqdn of schoolserver, callback) (sometime later, or immediately if already activated) v callback (as pid 2) v mount /sysroot, unmount usb/sd copy /security/lease to /sysroot/security/lease if first boot (activation) parse chosen/bootpath, swing /versions/current v make minimal userland context (mount --move /sysroot /) ideally protect PID 1, RTC <- vserver delta time v --------------------> (post-FRS) debian w/ developer key: | def run(): | os.exec('/sbin/init') if booting from a backup: If unpartitioned: 1. make new config w/ swapped current and alt (ie. create a /versions/configs/XXX w/ new current, alt) 2. then swing /versions/boot symlink If partitioned: 1. Make boot:/boot/alt/alt point to ../`basename(readlink boot:/boot)` 2. Make boot:/boot point to boot-versions/`basename(readlinke boot:/boot/alt)` create /versions/running symlink to pristine/<hash> xo boot: $current = basename of readlink of /versions/running (a hash) mnt /home /versions/run/$current/home (or /home from home partition) mnt /security /versions/run/$current/security (or /security from boot partition) mnt /versions /versions/run/$current/versions chroot /versions/run/$current (mount --move ?) v if exists '/sbin/olpc_init.py': sys.path = ['/sbin'] + sys.path from olpc_init import run run(<parameters?>) else: exec '/sbin/init --init' ---------------------> debian w/o developer key (in run) | pyinit + rainbow stuff (take over legacy init's job) fork run-parts (/etc/inittab stuff) listen for shutdown, etc. vserver (- CONTEXT)
Notes on P_SF_RUN
P_SF_RUN: off = allow mod = run from /versions/run/X on = pristine = run from /versions/run/X switch on->off: set the unlink flags on /versions/run off->on: create immutably-tagged /versions/run/a,b from /versions/a,b
List of directories in boot partition
/boot -> boot-versions/<hash> /boot-alt -> boot/alt /boot-versions/<version>/{runos.zip,runrd.zip,etc} /boot-versions/<version>/alt -> ../<alternate version> /security
List of directories in root partition
/sys, /proc, /ofw vfs /versions/pristine/{hashes} /versions/contents/{hashes} (contents files for the corresponding pristine tree) /versions/configs/`mkdtemp`/current -> ../../pristine/<hash> (backwards compatibility; don't use) /versions/configs/`mkdtemp`/alt -> ../../pristine/<hash> (backwards compatibility; don't use) /versions/boot -> configs/<something> (backwards compatibility; don't use) /versions/running -> pristine/<hash> (version we booted from; hash matches /boot symlink from boot partition) /versions/updates/<hash> (temporary space for updates, preserved in case update net connection drops & updater is restarted) /versions/run/{hashes} /security /boot -> versions/boot/current/boot (backwards compatibility; don't use) /boot-alt -> versions/boot/alt/boot (backwards compatibility; don't use)
List of directories in home partition
/home
Upgrade procedure
Upgrade procedure, creating new b from a (w.l.o.g) Rainbow: (ATC gives <version> <hash> <priority>) -1: Check that /versions/pristine/<hash> doesn't already exist. If unpartitioned: 0. Create new /versions/configs/$c <- where $c = mkdtemp 1. Create /versions/configs/$c/current -> realpath(/versions/running) 2. Swap /versions/boot to point to /versions/configs/$c, save old contents in $old If partitioned: 0-2. Make /boot/alt point to ../`basename /versions/running` 3a. Delete the tree(s) pointed to from /versions/configs/$old which are not pointed to by /versions/running (revisit when multiple trees) 3b. Delete corresponding members of /boot-versions if using a boot partition 4. Delete /versions/configs/$old. 4b. Delete corresponding member of /boot-versions if using a boot partition. 5. Invoke 'olpc-updater <version>' in new container: [MICHAEL WILL REWRITE STARTING FROM HERE] NOTE THAT /upgrade must live in same bind-mount as /current if we're to be able to clone it. MORE LIKELY THAT RAINBOW WILL CREATE /upgrade FOR US AS CLONE OF /current /current (ro-bind mount from /versions/a) /upgrade (initially empty) OLPC updater: 6. clone /current to /upgrade 7. upgrade /upgrade by hook or crook [END MICHAEL REWRITES] 8. exit Rainbow: 9. Verify /versions/updates/<hash> matches <hash> 10. Move /versions/updates/<hash> to /versions/pristine/<hash> 10b. Create /versions/run/<hash> from /versions/pristine/<hash> according to P_SF_RUN setting If unpartitioned: 11. Make a new config /versions/configs/$d (d = mkdtemp) 12. Create 'current' symlink to /versions/pristine/<hash> 13. Create 'alt' symlink to *realpath of* /versions/running 14. Swing /versions/boot to /versions/configs/$d (atomic! iff we do file move of new symlink) 15. Delete /versions/configs/$c If partitioned: 11. Copy /versions/pristine/<hash>/boot to boot:/boot-versions/<hash> 12. Make boot:/boot-versions/<hash>/alt point to what boot:/boot currently points to 13. Atomically swing boot:/boot to point to /boot-versions/<hash> 16. If <priority> reboot. (Ask Eben & sugar folks)
Open Questions
- Are thawed trees persistent?
- when I use a frozen tree?
- when I upgrade
- Is "thawness" global? Or per-OS-version?
- Can thawed trees be frozen for temporary read-only use?
- Space limits for upgrader?
- UI for:
- P_SF_RUN
- which image you boot (esp if more than two)
- Rest of security UI
- Configuration versioning / globalness
- do security settings persist across updates
- do we inherit a security configuration from the 'old' version when upgrading?
- Loadable kernel modules
- Bind-mount /lib/modules read-only? (Doesn't fix the problem, really)