install: Detect aboot images and enable the correct bootloader

Aboot images need to have the ostree bootloader backend set
to "aboot", otherwise the deploy during bootc install will
not create the correct boot A/B symlinks, and additionally
once booted will not correctly deploy to the aboot partition
during an update.

To see whethere an image is using aboot, we look for the "aboot.img"
file in the kernel modules dir.

NOTE: In order to correctly handle running bootc from a different
container than the to-be-installed container we look for aboot.img
in the actual commit, not just in the running container.

Author: alexlarsson

crates/lib/src/install.rs

@@ -779,6 +779,25 @@ async fn install_container(
     )?;
     let kargsd = kargsd.iter().map(|s| s.as_str());
 
+    // If the target uses aboot, then we need to set that bootloader in the ostree
+    // config before deploying the commit
+    if ostree_ext::bootabletree::commit_has_aboot_img(&merged_ostree_root, None)? {
+        tracing::debug!("Setting bootloader to aboot");
+        Command::new("ostree")
+            .args([
+                "config",
+                "--repo",
+                "ostree/repo",
+                "set",
+                "sysroot.bootloader",
+                "aboot",
+            ])
+            .cwd_dir(root_setup.physical_root.try_clone()?)
+            .run_capture_stderr()
+            .context("Setting bootloader config to aboot")?;
+        sysroot.repo().reload_config(None::<&gio::Cancellable>)?;
+    }
+
     // Keep this in sync with install/completion.rs for the Anaconda fixups
     let install_config_kargs = state
         .install_config

crates/ostree-ext/src/bootabletree.rs

@@ -12,6 +12,7 @@ use ostree::prelude::*;
 
 const MODULES: &str = "usr/lib/modules";
 const VMLINUZ: &str = "vmlinuz";
+const ABOOT_IMG: &str = "aboot.img";
 
 /// Find the kernel modules directory in a bootable OSTree commit.
 /// The target directory will have a `vmlinuz` file representing the kernel binary.
@@ -88,6 +89,20 @@ pub fn find_kernel_dir_fs(root: &Dir) -> Result<Option<Utf8PathBuf>> {
     Ok(r)
 }
 
+/// Check if there is an aboot image in the kernel tree dir
+pub fn commit_has_aboot_img(
+    root: &gio::File,
+    cancellable: Option<&gio::Cancellable>,
+) -> Result<bool> {
+    if let Some(kernel_dir) = find_kernel_dir(root, cancellable)? {
+        Ok(kernel_dir
+            .resolve_relative_path(ABOOT_IMG)
+            .query_exists(cancellable))
+    } else {
+        Ok(false)
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;