rdcore: Juggle physical root versus deployment root

docs/release-notes.md

@@ -6,6 +6,19 @@ nav_order: 8
 
 ## Upcoming coreos-installer 0.19.0 (unreleased)
 
+Major changes:
+
+
+Minor changes:
+
+
+Internal changes:
+
+- rootmap/bind-boot: Support root devices using composefs
+
+Packaging changes:
+
+
 
 ## coreos-installer 0.18.0 (2023-08-24)
 

src/bin/rdcore/main.rs

@@ -18,16 +18,16 @@ mod rootmap;
 mod stream_hash;
 mod unique_fs;
 
-use anyhow::Result;
+use anyhow::{Context, Result};
 use clap::Parser;
 
 use crate::cmdline::*;
 
 fn main() -> Result<()> {
     match Cmd::parse() {
         Cmd::Kargs(c) => kargs::kargs(c),
-        Cmd::Rootmap(c) => rootmap::rootmap(c),
-        Cmd::BindBoot(c) => rootmap::bind_boot(c),
+        Cmd::Rootmap(c) => rootmap::rootmap(c).context("Configuring rootmap"),
+        Cmd::BindBoot(c) => rootmap::bind_boot(c).context("Failed to bind boot"),
         Cmd::StreamHash(c) => stream_hash::stream_hash(c),
         Cmd::VerifyUniqueFsLabel(c) => unique_fs::verify_unique_fs(c),
         #[cfg(target_arch = "s390x")]

src/bin/rdcore/rootmap.rs

@@ -26,10 +26,17 @@ use libcoreinst::runcmd_output;
 
 use crate::cmdline::*;
 
+/// In the ostree model this will be the physical root mount.  When using
+/// composefs, the mount of / and /sysroot will be distinct.
+const PHYSICAL_ROOT_MOUNT: &str = "sysroot";
+
 pub fn rootmap(config: RootmapConfig) -> Result<()> {
-    // get the backing device for the root mount
-    let mount = Mount::from_existing(&config.root_mount)?;
-    let device = PathBuf::from(mount.device());
+    // Get the mount point for the deployment root, which will have e.g. /etc which we might parse
+    let rootfs_mount = Mount::from_existing(&config.root_mount)?;
+    // get the backing device for the "physical" root
+    let physical_root_path = format!("{}/{PHYSICAL_ROOT_MOUNT}", config.root_mount);
+    let physical_mount = Mount::from_existing(&physical_root_path)?;
+    let device = PathBuf::from(physical_mount.device());
 
     // and from that we can collect all the parent backing devices too
     let mut backing_devices = get_blkdev_deps_recursing(&device)?;
@@ -38,15 +45,18 @@ pub fn rootmap(config: RootmapConfig) -> Result<()> {
     // for each of those, convert them to kargs
     let mut kargs = Vec::new();
     for backing_device in backing_devices {
-        if let Some(dev_kargs) = device_to_kargs(&mount, backing_device)? {
+        if let Some(dev_kargs) = device_to_kargs(&rootfs_mount, backing_device)? {
             kargs.extend(dev_kargs);
         }
     }
 
     // we push the root kargs last, this has the nice property that the final order of kargs goes
     // from lowest level to highest; see also
     // https://github.com/coreos/fedora-coreos-tracker/issues/465
-    kargs.push(format!("root=UUID={}", mount.get_filesystem_uuid()?));
+    kargs.push(format!(
+        "root=UUID={}",
+        physical_mount.get_filesystem_uuid()?
+    ));
 
     // we need this because with root= it's systemd that takes care of mounting via
     // systemd-fstab-generator, and it defaults to read-only otherwise
@@ -224,7 +234,9 @@ fn get_luks_uuid(device: &Path) -> Result<String> {
 
 pub fn bind_boot(config: BindBootConfig) -> Result<()> {
     let boot_mount = Mount::from_existing(&config.boot_mount)?;
-    let root_mount = Mount::from_existing(&config.root_mount)?;
+    // We always operate here on the physical root
+    let physical_root_path = format!("{}/{PHYSICAL_ROOT_MOUNT}", config.root_mount);
+    let root_mount = Mount::from_existing(&physical_root_path)?;
     let boot_uuid = boot_mount.get_filesystem_uuid()?;
     let root_uuid = root_mount.get_filesystem_uuid()?;