install: Work around bootc-image-builder using /run/osbuild/containers

xref: osbuild/bootc-image-builder#560

Basically osbuild/bib puts the host `/var/lib/containers` at
`/run/osbuild/containers`. If we detect this situation, bind
mount it to `/var/lib/containers` so that the container
stack we invoke at install time can find logically bound
images.

Closes: containers#715

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

lib/src/install.rs

@@ -7,8 +7,8 @@
 // This sub-module is the "basic" installer that handles creating basic block device
 // and filesystem setup.
 pub(crate) mod baseline;
-mod osbuild;
 pub(crate) mod config;
+mod osbuild;
 pub(crate) mod osconfig;
 
 use std::io::Write;
@@ -1185,7 +1185,7 @@ async fn prepare_install(
     // creating multiple.
     let tempdir = cap_std_ext::cap_tempfile::TempDir::new(cap_std::ambient_authority())?;
     // And continue to init global state
-    osbuild::adjust_for_bootc_image_builder(&tempdir)?;
+    osbuild::adjust_for_bootc_image_builder(&rootfs, &tempdir)?;
 
     if !target_opts.skip_fetch_check {
         verify_target_fetch(&tempdir, &target_imgref).await?;

lib/src/install/osbuild.rs

@@ -41,10 +41,33 @@ fn adjust_etc_containers(tempdir: &Dir) -> Result<()> {
     Ok(())
 }
 
+/// osbuild mounts the host's /var/lib/containers at /run/osbuild/containers; mount
+/// it back to /var/lib/containers where the default container stack expects to find it.
+fn propagate_run_osbuild_containers(root: &Dir) -> Result<()> {
+    let osbuild_run_containers = Utf8Path::new("run/osbuild/containers");
+    // If we're not apparently running under osbuild, then we no-op.
+    if !root.try_exists(osbuild_run_containers)? {
+        return Ok(());
+    }
+    // If we do seem to have a valid container store though, use that
+    if crate::podman::storage_exists_default(root)? {
+        return Ok(());
+    }
+    let relative_storage = Utf8Path::new(crate::podman::CONTAINER_STORAGE.trim_start_matches('/'));
+    root.create_dir_all(relative_storage)?;
+    Task::new("Creating bind mount for run/osbuild/containers", "mount")
+        .arg("--rbind")
+        .args([osbuild_run_containers, relative_storage])
+        .cwd(root)?
+        .run()?;
+    Ok(())
+}
+
 /// bootc-image-builder today does a few things that we need to
 /// deal with.
 #[context("bootc-image-builder adjustments")]
-pub(crate) fn adjust_for_bootc_image_builder(tempdir: &Dir) -> Result<()> {
+pub(crate) fn adjust_for_bootc_image_builder(root: &Dir, tempdir: &Dir) -> Result<()> {
     adjust_etc_containers(tempdir)?;
+    propagate_run_osbuild_containers(root)?;
     Ok(())
 }

lib/src/podman.rs

@@ -1,4 +1,6 @@
 use anyhow::{anyhow, Result};
+use camino::Utf8Path;
+use cap_std_ext::cap_std::fs::Dir;
 use serde::Deserialize;
 
 use crate::install::run_in_host_mountns;
@@ -27,3 +29,21 @@ pub(crate) fn imageid_to_digest(imgid: &str) -> Result<String> {
         .ok_or_else(|| anyhow!("No images returned for inspect"))?;
     Ok(i.digest)
 }
+
+/// Return true if there is apparently an active container store at the target path.
+pub(crate) fn storage_exists(root: &Dir, path: impl AsRef<Utf8Path>) -> Result<bool> {
+    fn impl_storage_exists(root: &Dir, path: &Utf8Path) -> Result<bool> {
+        let lock = "storage.lock";
+        root.try_exists(path.join(lock)).map_err(Into::into)
+    }
+    impl_storage_exists(root, path.as_ref())
+}
+
+/// Return true if there is apparently an active container store in the default path
+/// for the target root.
+///
+/// Note this does not attempt to parse the root filesystem's container storage configuration,
+/// this uses a hardcoded default path.
+pub(crate) fn storage_exists_default(root: &Dir) -> Result<bool> {
+    storage_exists(root, CONTAINER_STORAGE.trim_start_matches('/'))
+}