install: Stop reading kargs from container root, use ostree

Part of containers#879

Basically we want to be able to `bootc install` outside of
a container. For the same reasons actually that we already support
parsing kargs from an ostree commit (without materializing it
as a filesystem), just expose a small wrapper for that API
via `pub(crate)` and use it in between the "pull" and "deploy" phases.

We basically do the same thing on `bootc upgrade`.

- v2: Clean up the multiple copies of the kargs path into a `const`

Signed-off-by: Colin Walters <[email protected]>

lib/src/install.rs

@@ -660,8 +660,6 @@ async fn install_container(
     let sepolicy = sepolicy.as_ref();
     let stateroot = state.stateroot();
 
-    let container_rootfs = &Dir::open_ambient_dir("/", cap_std::ambient_authority())?;
-
     let (src_imageref, proxy_cfg) = if !state.source.in_host_mountns {
         (state.source.imageref.clone(), None)
     } else {
@@ -703,17 +701,26 @@ async fn install_container(
 
     // Pull the container image into the target root filesystem. Since this is
     // an install path, we don't need to fsync() individual layers.
-    {
+    let pulled_image = {
         let spec_imgref = ImageReference::from(src_imageref.clone());
         let repo = &sysroot.repo();
         repo.set_disable_fsync(true);
-        crate::deploy::pull(repo, &spec_imgref, Some(&state.target_imgref), false).await?;
+        let r = crate::deploy::pull(repo, &spec_imgref, Some(&state.target_imgref), false).await?;
         repo.set_disable_fsync(false);
-    }
+        r
+    };
 
-    // Load the kargs from the /usr/lib/bootc/kargs.d from the running root,
-    // which should be the same as the filesystem we'll deploy.
-    let kargsd = crate::kargs::get_kargs_in_root(container_rootfs, std::env::consts::ARCH)?;
+    // We need to read the kargs from the target merged ostree commit before
+    // we do the deployment.
+    let merged_ostree_root = sysroot
+        .repo()
+        .read_commit(pulled_image.ostree_commit.as_str(), gio::Cancellable::NONE)?
+        .0;
+    let kargsd = crate::kargs::get_kargs_from_ostree_root(
+        &sysroot.repo(),
+        merged_ostree_root.downcast_ref().unwrap(),
+        std::env::consts::ARCH,
+    )?;
     let kargsd = kargsd.iter().map(|s| s.as_str());
 
     let install_config_kargs = state

lib/src/kargs.rs

@@ -15,6 +15,8 @@ use serde::Deserialize;
 use crate::deploy::ImageState;
 use crate::store::Storage;
 
+const KARGS_PATH: &str = "usr/lib/bootc/kargs.d";
+
 /// The kargs.d configuration file.
 #[derive(Deserialize)]
 #[serde(rename_all = "kebab-case", deny_unknown_fields)]
@@ -37,10 +39,7 @@ impl Config {
 /// a combined list.
 pub(crate) fn get_kargs_in_root(d: &Dir, sys_arch: &str) -> Result<Vec<String>> {
     // If the directory doesn't exist, that's OK.
-    let Some(d) = d
-        .open_dir_optional("usr/lib/bootc/kargs.d")?
-        .map(DirUtf8::from_cap_std)
-    else {
+    let Some(d) = d.open_dir_optional(KARGS_PATH)?.map(DirUtf8::from_cap_std) else {
         return Ok(Default::default());
     };
     let mut ret = Vec::new();
@@ -54,6 +53,18 @@ pub(crate) fn get_kargs_in_root(d: &Dir, sys_arch: &str) -> Result<Vec<String>>
 }
 
 /// Load kargs.d files from the target ostree commit root
+#[cfg(feature = "install")]
+pub(crate) fn get_kargs_from_ostree_root(
+    repo: &ostree::Repo,
+    root: &ostree::RepoFile,
+    sys_arch: &str,
+) -> Result<Vec<String>> {
+    let kargsd = root.resolve_relative_path(KARGS_PATH);
+    let kargsd = kargsd.downcast_ref::<ostree::RepoFile>().expect("downcast");
+    get_kargs_from_ostree(repo, kargsd, sys_arch)
+}
+
+/// Load kargs.d files from the target dir
 fn get_kargs_from_ostree(
     repo: &ostree::Repo,
     fetched_tree: &ostree::RepoFile,
@@ -119,7 +130,7 @@ pub(crate) fn get_kargs(
 
     // Get the kargs in kargs.d of the pending image
     let (fetched_tree, _) = repo.read_commit(fetched.ostree_commit.as_str(), cancellable)?;
-    let fetched_tree = fetched_tree.resolve_relative_path("/usr/lib/bootc/kargs.d");
+    let fetched_tree = fetched_tree.resolve_relative_path(KARGS_PATH);
     let fetched_tree = fetched_tree
         .downcast::<ostree::RepoFile>()
         .expect("downcast");