more thought
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THOUGHTS.txt
145
THOUGHTS.txt
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@ -1533,3 +1533,148 @@ Sun Apr 23 18:24:34 BST 2023
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- rotuer is not recognising when I set the hostname
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- I may have forgotten the root password :-(
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- why is hello world 70K unless hardeningDisable?
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Fri Apr 28 20:51:52 BST 2023
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To do nix-copy-closure we need nix-store, which is a symlink to nix,
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which is
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-rwxr-xr-x 1 dan users 2.3M Apr 28 21:08 nix
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(stripped). This is a lot bigger than, say, a simple script to
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loop through the closure of a derivation and copy only the store
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folders that don't exist already.
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* we'd like to only transmit the packages that aren't already present
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* we'd like to use a single ssh connection
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S: here is a list of package names
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C: these are the names of the packages I want
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S: here are the packages
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while read $f ; do
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test -d $f || echo $f
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end
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Tue May 2 21:53:08 BST 2023
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1) we have a script that runs on the receiver, which
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- accepts a list of store paths
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- prints the missing store paths
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- runs cpio -i < stdio
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2) we need a script for the sender that
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- refs=$(nix-store -q --references $1 && echo end)
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- opens ssh connection
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- print ssh $refs
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- needed= capture result until "end" received
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- find needed | cpio -o > ssh-connection
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- close connection
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3) to have a reasonable hope of testing this we should do it with qemu. It would be nice
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if we could connect without faff to the qemu lan interface : either we do this by bringing up
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another qemu vm (preferably with the host store shared, otherwise it has to build a mips cross
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compiler/libc) or maybe we could do something unholy with ssh ProxyCommand
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ssh -o ProxyCommand "socat - UDP4-DATAGRAM:230.0.0.1:1234,sourceport=1234,reuseaddr,ip-add-membership=230.0.0.1:127.0.0.1"
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4) we haven't solved garbage collection, though I think "remove everything not in
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nix-path-registration" might be what's needed there
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Wed May 3 22:01:19 BST 2023
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Something weird is going on with qemu net device enumeration: when I
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run it interactively I'm getting the access network (mac ending :02)
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on eth0 and the lan (mac ending :01) on eth1, and if it's behaving the
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same in CI then how come any of the tests work? vanilla-confinguration.nix
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definitely assumes lan=eth0
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By switching from -device virtio-net-pci to -device virtio-net then
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I get the desired behaviour back
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Sat May 6 18:42:28 BST 2023
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Next:
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- package min-copy-closure
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- see if we can use it on some output to copy the whole system closure
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- post-copying symlink munging
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- try it on a real device, see if it works for config file updates
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- collect-garbage/delete-old-generation
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Sun May 7 23:03:03 BST 2023
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Shortly after all the work to reduce system closure size last time, I
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tried adding the necessary packages to support nix-copy-closure and
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saw it start building a complete C++ system with Boost. My fears that
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this would lead to quite a large increase in the system size were, it
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turned out, entirely founded.
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So I wrote my own - or at least, a quite minimal substitute. The core
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logic is simple - on the sender, we get the list of required packages,
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then we check for the existence of `/nix/store/eeeeeee-foo` for
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each of them on the target, and whatever's missing we send across the
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link using cpio.
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It sounds simple, and it should be simple, and in retrospect it _was_
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simple. Along the way I went on a bit of a Qemu networking tangent and
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learned quite a lot about the bash `coproc` command
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Tue May 9 21:06:53 BST 2023
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General direction of my thoughts:
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- get a baseline working rotuer system
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- prove that min-copy-closure works with it
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- refactor the crap out of it
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- configurablise the bordervm usb ethernet setup
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- when we have a good idea of how/whether min-copy-closure *actually*
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works, declare "writeable filesystem" to be done
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- start to get more of a feel for how the services/config hang together
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? why does rotuer not have a hostname?
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? how can we get a device hooked up to rotuer's lan port that we can
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control remotely
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Sun May 14 23:25:46 BST 2023
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the outputs.systemConfiguration attribute builds a derivation
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containing a single file bin/activate
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_Presumably_, copying its closure will copy all the things, as
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we already use it as the roots for jffs2 creation. However, there
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is also a symlink created from /init at jffs2 creation
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Mon May 15 21:32:38 BST 2023
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Had a neat idea about uing an overlayfs combining jffs2 and ramfs
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to do upgrades that would otherwise be larger than the flash.
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Could use "overlay merge" from https://github.com/kmxz/overlayfs-tools
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Wed May 17 15:18:55 BST 2023
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liminix-rebuild doesn't collect garbage (this is a mising feature, not
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a bug). We think we can fix this using nix-path-registration: specifically,
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by deleting anything not in it.
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What we're going to do: build a fresh system image for rotuer, then
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dogfood liminix-rebuild until we've succeeded in getting it to
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change its hostname
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Also wondering if we should drop outputs.default, but maybe not
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* systemConfiguration: used for updates
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* vmroot: used for qemu
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* flashimage: used for flashing
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* tftproot: used for dev/test
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As long as we're consistently setting the default output to whichever
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is the appropriate "full production image" I think we're good.
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