install: Enable installing to devices with multiple parents

Assisted-by: Claude Code (Opus 4)
Signed-off-by: ckyrouac <ckyrouac@redhat.com>

Author: ckyrouac

crates/lib/src/bootloader.rs

@@ -67,6 +67,48 @@ pub(crate) fn supports_bootupd(root: &Dir) -> Result<bool> {
     Ok(r)
 }
 
+/// Check whether the target bootupd supports `--filesystem`.
+///
+/// Runs `bootupctl backend install --help` and looks for `--filesystem` in the
+/// output. When `deployment_path` is set the command runs inside a bwrap
+/// container so we probe the binary from the target image.
+fn bootupd_supports_filesystem(rootfs: &Utf8Path, deployment_path: Option<&str>) -> Result<bool> {
+    let help_args = ["bootupctl", "backend", "install", "--help"];
+    let output = if let Some(deploy) = deployment_path {
+        let target_root = rootfs.join(deploy);
+        BwrapCmd::new(&target_root)
+            .setenv(
+                "PATH",
+                "/bin:/usr/bin:/sbin:/usr/sbin:/usr/local/bin:/usr/local/sbin",
+            )
+            .run_get_string(help_args)?
+    } else {
+        Command::new("bootupctl")
+            .args(&help_args[1..])
+            .log_debug()
+            .run_get_string()?
+    };
+
+    let use_filesystem = output.contains("--filesystem");
+
+    if use_filesystem {
+        tracing::debug!("bootupd supports --filesystem");
+    } else {
+        tracing::debug!("bootupd does not support --filesystem, falling back to --device");
+    }
+
+    Ok(use_filesystem)
+}
+
+/// Install the bootloader via bootupd.
+///
+/// When the target bootupd supports `--filesystem` we pass it pointing at a
+/// block-backed mount so that bootupd can resolve the backing device(s) itself
+/// via `lsblk`.  In the bwrap path we bind-mount the physical root at
+/// `/sysroot` to give `lsblk` a real block-backed path.
+///
+/// For older bootupd versions that lack `--filesystem` we fall back to the
+/// legacy `--device <device_path> <rootfs>` invocation.
 #[context("Installing bootloader")]
 pub(crate) fn install_via_bootupd(
     device: &bootc_blockdev::Device,
@@ -91,8 +133,6 @@ pub(crate) fn install_via_bootupd(
 
     println!("Installing bootloader via bootupd");
 
-    let device_path = device.path();
-
     // Build the bootupctl arguments
     let mut bootupd_args: Vec<&str> = vec!["backend", "install"];
     if configopts.bootupd_skip_boot_uuid {
@@ -107,26 +147,55 @@ pub(crate) fn install_via_bootupd(
     if let Some(ref opts) = bootupd_opts {
         bootupd_args.extend(opts.iter().copied());
     }
-    bootupd_args.extend(["--device", &device_path, rootfs_mount]);
+
+    // When the target bootupd lacks --filesystem support, fall back to the
+    // legacy --device flag.  For --device we need the whole-disk device path
+    // (e.g. /dev/vda), not a partition (e.g. /dev/vda3), so resolve the
+    // parent via require_single_root().  (Older bootupd doesn't support
+    // multiple backing devices anyway.)
+    // Computed before building bootupd_args so the String lives long enough.
+    let root_device_path = if bootupd_supports_filesystem(rootfs, deployment_path)
+        .context("Probing bootupd --filesystem support")?
+    {
+        None
+    } else {
+        Some(device.require_single_root()?.path())
+    };
+    if let Some(ref dev) = root_device_path {
+        tracing::debug!("bootupd does not support --filesystem, falling back to --device {dev}");
+        bootupd_args.extend(["--device", dev]);
+        bootupd_args.push(rootfs_mount);
+    } else {
+        tracing::debug!("bootupd supports --filesystem");
+        bootupd_args.extend(["--filesystem", rootfs_mount]);
+        bootupd_args.push(rootfs_mount);
+    }
 
     // Run inside a bwrap container. It takes care of mounting and creating
     // the necessary API filesystems in the target deployment and acts as
     // a nicer `chroot`.
     if let Some(deploy) = deployment_path {
         let target_root = rootfs.join(deploy);
         let boot_path = rootfs.join("boot");
+        let rootfs_path = rootfs.to_path_buf();
 
         tracing::debug!("Running bootupctl via bwrap in {}", target_root);
 
         // Prepend "bootupctl" to the args for bwrap
         let mut bwrap_args = vec!["bootupctl"];
         bwrap_args.extend(bootupd_args);
 
-        let cmd = BwrapCmd::new(&target_root)
+        let mut cmd = BwrapCmd::new(&target_root)
             // Bind mount /boot from the physical target root so bootupctl can find
             // the boot partition and install the bootloader there
             .bind(&boot_path, &"/boot");
 
+        // Only bind mount the physical root at /sysroot when using --filesystem;
+        // bootupd needs it to resolve backing block devices via lsblk.
+        if root_device_path.is_none() {
+            cmd = cmd.bind(&rootfs_path, &"/sysroot");
+        }
+
         // The $PATH in the bwrap env is not complete enough for some images
         // so we inject a reasonnable default.
         // This is causing bootupctl and/or sfdisk binaries

crates/lib/src/install.rs

@@ -2564,9 +2564,8 @@ pub(crate) async fn install_to_filesystem(
     // Find the real underlying backing device for the root.  This is currently just required
     // for GRUB (BIOS) and in the future zipl (I think).
     let device_info = {
-        let dev =
-            bootc_blockdev::list_dev(Utf8Path::new(&inspect.source))?.require_single_root()?;
-        tracing::debug!("Backing device: {}", dev.path());
+        let dev = bootc_blockdev::list_dev(Utf8Path::new(&inspect.source))?;
+        tracing::debug!("Target filesystem backing device: {}", dev.path());
         dev
     };
 

crates/utils/src/bwrap.rs

@@ -59,8 +59,8 @@ impl<'a> BwrapCmd<'a> {
         self
     }
 
-    /// Run the specified command inside the container.
-    pub fn run<S: AsRef<OsStr>>(self, args: impl IntoIterator<Item = S>) -> Result<()> {
+    /// Build the bwrap `Command` with all bind mounts, env vars, and args.
+    fn build_command<S: AsRef<OsStr>>(&self, args: impl IntoIterator<Item = S>) -> Command {
         let mut cmd = Command::new("bwrap");
 
         // Bind the root filesystem
@@ -92,6 +92,21 @@ impl<'a> BwrapCmd<'a> {
         cmd.arg("--");
         cmd.args(args);
 
-        cmd.log_debug().run_inherited_with_cmd_context()
+        cmd
+    }
+
+    /// Run the specified command inside the container.
+    pub fn run<S: AsRef<OsStr>>(self, args: impl IntoIterator<Item = S>) -> Result<()> {
+        self.build_command(args)
+            .log_debug()
+            .run_inherited_with_cmd_context()
+    }
+
+    /// Run the specified command inside the container and capture stdout as a string.
+    pub fn run_get_string<S: AsRef<OsStr>>(
+        self,
+        args: impl IntoIterator<Item = S>,
+    ) -> Result<String> {
+        self.build_command(args).log_debug().run_get_string()
     }
 }

hack/provision-derived.sh

@@ -69,6 +69,48 @@ resize_rootfs: false
 CLOUDEOF
 fi
 
+# Temporary: update bootupd from @CoreOS/continuous copr until
+# CentOS Stream 10 base image includes a version supporting --filesystem
+. /usr/lib/os-release
+case "${ID}-${VERSION_ID}" in
+    "centos-10"|"rhel-10."*)
+        case $ID in
+            fedora) copr_distro="fedora" ;;
+            *) copr_distro="centos-stream" ;;
+        esac
+        # Update bootc first from rhcontainerbot copr; the new bootupd
+        # requires a newer bootc than what ships in the base image.
+        cat >/etc/yum.repos.d/rhcontainerbot-bootc.repo <<REPOEOF
+[copr:copr.fedorainfracloud.org:rhcontainerbot:bootc]
+name=Copr repo for bootc owned by rhcontainerbot
+baseurl=https://download.copr.fedorainfracloud.org/results/rhcontainerbot/bootc/${copr_distro}-\$releasever-\$basearch/
+type=rpm-md
+skip_if_unavailable=True
+gpgcheck=1
+gpgkey=https://download.copr.fedorainfracloud.org/results/rhcontainerbot/bootc/pubkey.gpg
+repo_gpgcheck=0
+enabled=1
+enabled_metadata=1
+REPOEOF
+        dnf -y update bootc
+        rm -f /etc/yum.repos.d/rhcontainerbot-bootc.repo
+        cat >/etc/yum.repos.d/coreos-continuous.repo <<REPOEOF
+[copr:copr.fedorainfracloud.org:group_CoreOS:continuous]
+name=Copr repo for continuous owned by @CoreOS
+baseurl=https://download.copr.fedorainfracloud.org/results/@CoreOS/continuous/${copr_distro}-\$releasever-\$basearch/
+type=rpm-md
+skip_if_unavailable=True
+gpgcheck=1
+gpgkey=https://download.copr.fedorainfracloud.org/results/@CoreOS/continuous/pubkey.gpg
+repo_gpgcheck=0
+enabled=1
+enabled_metadata=1
+REPOEOF
+        dnf -y install bootupd-0.2.32.41.gb788553
+        rm -f /etc/yum.repos.d/coreos-continuous.repo
+        ;;
+esac
+
 dnf clean all
 # Stock extra cleaning of logs and caches in general (mostly dnf)
 rm /var/log/* /var/cache /var/lib/{dnf,rpm-state,rhsm} -rf

tmt/plans/integration.fmf

@@ -222,4 +222,11 @@ execute:
     how: fmf
     test:
       - /tmt/tests/tests/test-38-install-bootloader-none
+
+/plan-39-multi-device-esp:
+  summary: Test multi-device ESP detection for to-existing-root
+  discover:
+    how: fmf
+    test:
+      - /tmt/tests/test-39-multi-device-esp
 # END GENERATED PLANS