Port the init binary code to Rust by jakecorrenti · Pull Request #670 · containers/libkrun

jakecorrenti · 2026-05-07T03:51:01Z

This PR ports the init binary code to Rust. It acts like any of the other crates that we have within the project.

To run the examples or with Podman, you would build the project as usual: make BLK=1 NET=1 && sudo make BLK=1 NET=1 install and continue with business as usual.

In my testing I've found the init binary to still remain small:

libkrun/init port-init ≡
❯ ll ../target/release/krun-init
.rwxr-xr-x@ 657k jcorrent  4 Jun 11:16 -I ../target/release/krun-init

NOTE: the AWS Nitro init binary is still written in C and will be ported next.

Fixes: #632

jakecorrenti · 2026-06-04T15:14:11Z

@nohajc if you could give this a try on FreeBSD that would be awesome :)

nohajc · 2026-06-04T15:15:43Z

@jakecorrenti I'll see what I can do. :)

nohajc

Currently, passing the command-line on FreeBSD is broken. See my comment.

This also reveals an issue in integration tests because you can see they TIMEOUT but the test run is marked as successful anyway. Not sure why...

nohajc · 2026-06-04T20:11:59Z

+}
+
+pub fn load(#[cfg(target_os = "linux")] is_mount_point: impl Fn(&str) -> bool) -> Config {
+    let path = env::var("KRUN_CONFIG").unwrap_or_else(|_| CONFIG_FILE_PATH.to_string());


Already found an issue when I noticed in the github action log that ISO_CONFIG_PATH is unused. It needs to be used instead of CONFIG_FILE_PATH on FreeBSD.

~~seems like things are running ok so far and added the fix you suggested~~ timed out again, but not sure what's going on. i don't have a FreeBSD machine so i will have to figure it out

I can try to play with it more tomorrow. Anyway, you should be able to run the full integration test including FreeBSD guest cases locally on either macOS or Linux. It downloads the sysroot and all other dependencies automatically.

FreeBSD tests are skipped by default but they should run once init-freebsd is first compiled.

Add init/src/config.rs, replacing the hand-rolled jsmn-based parser with serde_json. Parses /.krun_config.json (or KRUN_CONFIG env var) and returns a Config struct with: - argv: Entrypoint ++ (args | Cmd), or None if absent - workdir: WorkingDir or Cwd - tmpfs: first tmpfs mount destination not already mounted Environment variables from the Env array are applied during parsing, with HOME and TERM always overwritten, all others set only if unset. A missing or unparseable config file is silently ignored. Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Add setup_network() and setup_dhcp() to env.rs. setup_network() brings up lo unconditionally. setup_dhcp() checks that the interface exists before calling do_dhcp(), and logs a warning on failure rather than aborting (DHCP failure is non-fatal — the VM may be IPv6-only or have no network). Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Extend env.rs with: - apply_hostname(): sets hostname from HOSTNAME env var, defaulting to "localhost" - apply_env(): maps KRUN_HOME -> HOME and KRUN_TERM -> TERM - apply_rlimits(): parses the KRUN_RLIMITS comma-separated list of id,cur,max triples and applies each via setrlimit(2) Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Add exec.rs with: - setup_redirects(): walks /sys/class/virtio-ports and dup2s krun-stdin/stdout/stderr onto the corresponding file descriptors - set_exit_code(): reports the workload exit code to the host via KRUN_EXIT_CODE_IOCTL, only when the root fs is virtiofs - run_workload(): forks so PID 1 can reap children; the child calls exec_workload() which sets up redirects and execvp's the argv. Parent waits for the child, reports exit code, syncs, and reboots. KRUN_INIT_PID1=1 skips the fork and exec_workload directly as PID 1. Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Connect all modules in main() in order: 1. mount_block_root() [amd-sev | tdx] 2. mount_filesystems() 3. mount_block_root_device() [KRUN_BLOCK_ROOT_DEVICE] 4. mount_shared_root() 5. setsid + TIOCSCTTY 6. setup_network() 7. config::load() 8. mount_tmpfs() [config tmpfs mount] 9. apply_env / apply_hostname / apply_rlimits 10. chdir to workdir 11. run_workload(argv) Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Add init/src/freebsd.rs with: - kenv_get(): reads a variable from the FreeBSD kernel environment via kenv(2), which is the source of env vars for init before the process environment is set up - populate_env_from_kenv(): imports the known KRUN_* variables from kenv into std::env at startup so the rest of the code can use std::env::var uniformly on both platforms - open_console(): replicates login_tty(3) without linking libutil — revokes existing opens of /dev/console, opens it, creates a new session via setsid(2), sets the controlling terminal via TIOCSCTTY, and dup2s it onto stdio; falls back to /dev/null + /init.log - mount_config_iso() / unmount_config_iso(): mounts the KRUN_CONFIG ISO 9660 image at /mnt via nmount(2) so the JSON config file can be read, then unmounts it afterwards Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Connect the FreeBSD helpers into the boot sequence: - open_console() and populate_env_from_kenv() are called at the very start of main() before anything else - setsid/TIOCSCTTY are Linux-only; open_console() handles session setup on FreeBSD - setlogin("root") is called on FreeBSD after console setup - KRUN_DHCP and DHCP setup are Linux-only - If KRUN_CONFIG is not set, mount_config_iso() is attempted; the ISO is unmounted immediately after config::load() returns - fs::* mounts and mount_shared_root are Linux-only - exec_workload() calls open_console() on FreeBSD instead of setup_redirects(), giving the child process a fresh controlling terminal before execvp Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Replace the C-based BSD init build rule (which referenced the now-deleted init/init.c) with a cargo build rule targeting the correct Rust triple. Makefile: - Remove dead INIT_SRC = init/init.c variable. - Derive FREEBSD_RUST_TARGET from the host ARCH with arm64→aarch64 substitution to get the correct Rust triple. - Set CARGO_BSD_RUSTFLAGS with the clang cross-linker flags (mirroring the existing CC_BSD setup) so cargo can link for FreeBSD. - aarch64-unknown-freebsd is a Tier 3 target with no prebuilt std; use +nightly -Z build-std for that case. setup-build-env: - Add rustup target add x86_64-unknown-freebsd (Tier 2, prebuilt std). - Install nightly toolchain + rust-src for the aarch64 FreeBSD case. cross-compilation.yml: - Add clang to the Linux cross-compilation dependencies so the FreeBSD linker flags resolve correctly on Linux runners. Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Implements the timesync feature behind the `timesync` cargo feature flag. Receives host-side nanosecond timestamps over AF_VSOCK/SOCK_DGRAM on port 123 and applies them via clock_settime when the delta exceeds 100ms. Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Delete init/init.c, init/dhcp.c, init/dhcp.h, init/jsmn.h, and the entire init/tee/ directory (snp_attest.c/h and the KBS client). The amd-sev feature no longer performs LUKS unlock or KBS attestation — it mounts /dev/vda as ext4 like the tdx path does. Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me> Assisted-by: Claude Code:claude-sonnet-4.6

Port of cd8b2be. The temporary root directory hack has been replaced by NullFs, so the ioctl that cleaned it up is no longer needed. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

Port of 2593acc. When TSI is active, brings up dummy0 and assigns it 10.0.0.1/8 so applications that probe for network availability see a configured interface. Silently skips setup if the dummy driver is absent in the kernel. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

The non-Linux setup_network() stub was empty, so the lo interface was never raised inside FreeBSD guests. The C init unconditionally brought up lo on all platforms (the #if __linux__ guard covered only the DHCP block, not lo setup). Use nix::sys::socket to open an AF_INET/SOCK_DGRAM socket and issue SIOCSIFFLAGS / IFF_UP, matching the C behaviour. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

The C init accepted "Cmd", "Env", "WorkingDir"/"Cwd", and "Entrypoint" keys via case-insensitive comparison; the Rust port only handled OCI runtime-spec keys ("args", "env", "cwd" inside "process"). Add serde aliases so RawConfig's flat fields also accept the Docker image config capitalisation: - "Cmd" aliases "args" - "Env" aliases "env" - "WorkingDir"/"Cwd" alias "cwd" - new "Entrypoint" field (top-level, Docker format only) When Entrypoint is present it is prepended to the resolved args vector, matching the C init's concat_entrypoint_argv() behaviour. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

Two issues with apply_rlimits(): 1. The C init parsed KRUN_RLIMITS with strtoull() and a single-char skip, so any separator character between ID, CUR, and MAX worked (e.g. "7:1024:4096"). The Rust code required "ID=CUR:MAX" and silently skipped entries using the historical colon-only format. 2. krun_set_rlimits() wraps the entire value in double-quotes (format!("\"{}\"", ...)), so the env var received by init is "\"7=1024:4096\"". Neither the old Rust nor the C parser handled this correctly. Fix both by extracting parse_rlimit_entry() which strips outer '"' chars and splits on the first two occurrences of '=' or ':' via splitn(3). Both formats and the quoted form now parse correctly. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

The C init replaced argv[0] with "/bin/sh" when neither KRUN_INIT nor a config file was present, forwarding remaining cmdline tokens as shell arguments. The Rust init instead treats proc_args[1] as the executable directly. Add a comment explaining the rationale: callers that omit both KRUN_INIT and a config file intend the cmdline argument to be the command, not a shell script path, making the Rust behaviour more intuitive. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

A thread is destroyed when the parent calls execvp() (in PID1 mode). The C init ran clock_worker() in a forked child process, which survives exec. Match that behaviour: create the vsock socket, fork, and run the recv loop in the child; the parent closes its copy of the socket and returns immediately. Also switch to nix wrappers throughout: socket::socket(), socket::recv(), time::clock_gettime(), and time::clock_settime() replace the equivalent unsafe libc calls. Add the nix "time" feature to support the clock functions. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

The C init called exit(125) if setup_redirects() returned a negative value (which it did when opendir("/sys/class/virtio-ports") failed). The Rust port returned silently, letting the workload run with unredirected stdio and no diagnostic. Match the C behaviour: print an error and exit(125) so callers get a visible signal that the redirects could not be set up. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

The C init checked *env_init_pid1 == '1' (first-byte comparison), accepting any value starting with '1' — including "10" or "1\n" (which can appear when the value originates from a file read). The Rust port used exact equality with "1", silently ignoring those variants. Replace with is_ok_and(|v| v.starts_with('1')). Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

Port of upstream commit 378e524 ("init/dhcp: only overwrite resolv.conf with DNS"). Only write /etc/resolv.conf when the DHCP server provides nameservers, preserving any pre-existing content. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

jakecorrenti mentioned this pull request May 7, 2026

init: fix unescape_string not advancing past escape characters #669

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jakecorrenti force-pushed the port-init branch from 26906cb to d631636 Compare May 7, 2026 04:25

mtjhrc reviewed May 7, 2026

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Comment thread src/init-blob/build.rs

jakecorrenti force-pushed the port-init branch 18 times, most recently from 1719f2f to 9933316 Compare May 11, 2026 18:01

jakecorrenti mentioned this pull request May 11, 2026

Replace hardcoded init.krun with generic virtual file overlay #673

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jakecorrenti force-pushed the port-init branch from 9933316 to 2a0a08b Compare May 13, 2026 01:01

jakecorrenti mentioned this pull request May 13, 2026

quoting issues for environment variables passed from podman #678

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mtjhrc mentioned this pull request May 20, 2026

lib: remove deprecated APIs and implicit resource creation #688

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mtjhrc mentioned this pull request May 28, 2026

--user flag not respected under (rootless) podman #123

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jakecorrenti force-pushed the port-init branch 4 times, most recently from d2db78e to 9a86b2f Compare May 29, 2026 20:12

jakecorrenti changed the title ~~WIP: Port the init binary code to Rust~~ Port the init binary code to Rust Jun 4, 2026

jakecorrenti marked this pull request as ready for review June 4, 2026 15:13

jakecorrenti requested review from MatiasVara, dorindabassey, slp and tylerfanelli as code owners June 4, 2026 15:13

nohajc suggested changes Jun 4, 2026

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jakecorrenti added 20 commits June 4, 2026 16:28

init: remove KRUN_REMOVE_ROOT_DIR_IOCTL

22b661c

Port of cd8b2be. The temporary root directory hack has been replaced by NullFs, so the ioctl that cleaned it up is no longer needed. Assisted-by: Claude Code: claude-sonnet-4-6 Signed-off-by: Jake Correnti <jakecorrenti+github@proton.me>

jakecorrenti force-pushed the port-init branch from 3a3b1a0 to 61c7a92 Compare June 4, 2026 20:29

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Port the init binary code to Rust#670

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