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diff --git a/tvix/boot/README.md b/tvix/boot/README.md new file mode 100644 index 0000000000..13a4855060 --- /dev/null +++ b/tvix/boot/README.md @@ -0,0 +1,136 @@ +# tvix/boot + +This directory provides tooling to boot VMs with /nix/store provided by +virtiofs. + +In the `tests/` subdirectory, there's some integration tests. + +## //tvix/boot:runVM +A script spinning up a `tvix-store virtiofs` daemon, then starting a cloud- +hypervisor VM. + +The cloud-hypervisor VM is using a (semi-)minimal kernel image with virtiofs +support, and a custom initrd (using u-root). It supports various command line +options, to be able to do VM tests, act as an interactive shell or exec a binary +from a closure. + +It supports the following env vars: + - `CH_NUM_CPUS=1` controls the number of CPUs available to the VM + - `CH_MEM_SIZE=512M` controls the memory availabe to the VM + - `CH_CMDLINE=` controls the kernel cmdline (which can be used to control the + boot) + +### Usage +First, ensure you have `tvix-store` in `$PATH`, as that's what `run-tvix-vm` +expects: + +Assuming you ran `cargo build --profile=release-with-debug` before, and are in +the `tvix` directory: + +``` +export PATH=$PATH:$PWD/target/release-with-debug +``` + +Secondly, configure tvix to use the local backend: + +``` +export BLOB_SERVICE_ADDR=sled://$PWD/blobs.sled +export DIRECTORY_SERVICE_ADDR=sled://$PWD/directories.sled +export PATH_INFO_SERVICE_ADDR=sled://$PWD/pathinfo.sled +``` + +Potentially copy some data into tvix-store (via nar-bridge): + +``` +mg run //tvix:store -- daemon & +$(mg build //tvix:nar-bridge)/bin/nar-bridge-http & +rm -Rf ~/.cache/nix; nix copy --to http://localhost:9000\?compression\=none $(mg build //third_party/nixpkgs:hello) +pkill nar-bridge-http; pkill tvix-store +``` + +#### Interactive shell +Run the VM like this: + +``` +CH_CMDLINE=tvix.shell mg run //tvix/boot:runVM -- +``` + +You'll get dropped into an interactive shell, from which you can do things with +the store: + +``` + ______ _ ____ _ __ + /_ __/ __(_) __ / _/___ (_) /_ + / / | | / / / |/_/ / // __ \/ / __/ + / / | |/ / /> < _/ // / / / / /_ +/_/ |___/_/_/|_| /___/_/ /_/_/\__/ + +/# ls -la /nix/store/ +dr-xr-xr-x root 0 0 Jan 1 00:00 . +dr-xr-xr-x root 0 989 Jan 1 00:00 aw2fw9ag10wr9pf0qk4nk5sxi0q0bn56-glibc-2.37-8 +dr-xr-xr-x root 0 3 Jan 1 00:00 jbwb8d8l28lg9z0xzl784wyb9vlbwss6-xgcc-12.3.0-libgcc +dr-xr-xr-x root 0 82 Jan 1 00:00 k8ivghpggjrq1n49xp8sj116i4sh8lia-libidn2-2.3.4 +dr-xr-xr-x root 0 141 Jan 1 00:00 mdi7lvrn2mx7rfzv3fdq3v5yw8swiks6-hello-2.12.1 +dr-xr-xr-x root 0 5 Jan 1 00:00 s2gi8pfjszy6rq3ydx0z1vwbbskw994i-libunistring-1.1 +``` + +Once you exit the shell, the VM will power off itself. + +#### Execute a specific binary +Run the VM like this: + +``` +hello_cmd=$(mg build //third_party/nixpkgs:hello)/bin/hello +CH_CMDLINE=tvix.run=$hello_cmd mg run //tvix/boot:runVM -- +``` + +Observe it executing the file (and closure) from the tvix-store: + +``` +[ 0.277486] Run /init as init process + ______ _ ____ _ __ + /_ __/ __(_) __ / _/___ (_) /_ + / / | | / / / |/_/ / // __ \/ / __/ + / / | |/ / /> < _/ // / / / / /_ +/_/ |___/_/_/|_| /___/_/ /_/_/\__/ + +Hello, world! +2023/09/24 21:10:19 Nothing left to be done, powering off. +[ 0.299122] ACPI: PM: Preparing to enter system sleep state S5 +[ 0.299422] reboot: Power down +``` + +#### Execute a NixOS system closure +It's also possible to invoke a system closure. To do this, tvix-init honors the +init= cmdline option, and will switch_root to it. + + +``` +CH_CMDLINE=init=/nix/store/…-nixos-system-…/init mg run //tvix/boot:runVM -- +``` + +``` + ______ _ ____ _ __ + /_ __/ __(_) __ / _/___ (_) /_ + / / | | / / / |/_/ / // __ \/ / __/ + / / | |/ / /> < _/ // / / / / /_ +/_/ |___/_/_/|_| /___/_/ /_/_/\__/ + +2023/09/24 21:16:43 switch_root: moving mounts +2023/09/24 21:16:43 switch_root: Skipping "/run" as the dir does not exist +2023/09/24 21:16:43 switch_root: Changing directory +2023/09/24 21:16:43 switch_root: Moving / +2023/09/24 21:16:43 switch_root: Changing root! +2023/09/24 21:16:43 switch_root: Deleting old / +2023/09/24 21:16:43 switch_root: executing init + +<<< NixOS Stage 2 >>> + +[ 0.322096] booting system configuration /nix/store/g657sdxinpqfcdv0162zmb8vv9b5c4c5-nixos-system-client-23.11.git.82102fc37da +running activation script... +setting up /etc... +starting systemd... +[ 0.980740] systemd[1]: systemd 253.6 running in system mode (+PAM +AUDIT -SELINUX +APPARMOR +IMA +SMACK +SECCOMP +GCRYPT -GNUTLS +OPENSSL +ACL +BLKID +CURL +ELFUTILS +FIDO2 +IDN2 -IDN +IPTC +KMOD +LIBCRYPTSETUP +LIBFDISK +PCRE2 -PWQUALITY +P11KIT -QRENCODE +TPM2 +BZIP2 +LZ4 +XZ +ZLIB +ZSTD +BPF_FRAMEWORK -XKBCOMMON +UTMP -SYSVINIT default-hierarchy=unified) +``` + +This effectively replaces the NixOS Stage 1 entirely. |