install: Drop need for -v /:/target

Build on our new logic for bind mounting from the host mountns
to also drop the need for the `-v /:/target` in the alongside
install code.

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

lib/src/install.rs

@@ -40,6 +40,7 @@ use ostree_ext::ostree;
 use ostree_ext::prelude::Cast;
 use ostree_ext::sysroot::SysrootLock;
 use rustix::fs::{FileTypeExt, MetadataExt as _};
+use rustix::thread::Pid;
 use serde::{Deserialize, Serialize};
 
 use self::baseline::InstallBlockDeviceOpts;
@@ -56,6 +57,8 @@ use crate::utils::sigpolicy_from_opts;
 const BOOT: &str = "boot";
 /// Directory for transient runtime state
 const RUN_BOOTC: &str = "/run/bootc";
+/// The default path for the host rootfs
+const ALONGSIDE_ROOT_MOUNT: &str = "/target";
 /// This is an ext4 special directory we need to ignore.
 const LOST_AND_FOUND: &str = "lost+found";
 /// The filename of the composefs EROFS superblock; TODO move this into ostree
@@ -316,9 +319,10 @@ pub(crate) struct InstallToExistingRootOpts {
     #[clap(long)]
     pub(crate) acknowledge_destructive: bool,
 
-    /// Path to the mounted root; it's expected to invoke podman with
-    /// `-v /:/target`, then supplying this argument is unnecessary.
-    #[clap(default_value = "/target")]
+    /// Path to the mounted root; this is now not necessary to provide.
+    /// Historically it was necessary to ensure the host rootfs was mounted at here
+    /// via e.g. `-v /:/target`.
+    #[clap(default_value = ALONGSIDE_ROOT_MOUNT)]
     pub(crate) root_path: Utf8PathBuf,
 }
 
@@ -1631,6 +1635,22 @@ pub(crate) async fn install_to_filesystem(
     // And the last bit of state here is the fsopts, which we also destructure now.
     let mut fsopts = opts.filesystem_opts;
 
+    // If we're doing an alongside install, automatically set up the host rootfs
+    // mount if it wasn't done already.
+    if targeting_host_root
+        && fsopts.root_path.as_str() == ALONGSIDE_ROOT_MOUNT
+        && !fsopts.root_path.try_exists()?
+    {
+        std::fs::create_dir(ALONGSIDE_ROOT_MOUNT)?;
+        crate::mount::bind_mount_from_pidns(
+            Pid::from_raw(1).unwrap(),
+            "/".into(),
+            ALONGSIDE_ROOT_MOUNT.into(),
+            true,
+        )
+        .context("Mounting host / to {ALONGSIDE_ROOT_MOUNT}")?;
+    }
+
     // Check that the target is a directory
     {
         let root_path = &fsopts.root_path;

tests-integration/src/install.rs

@@ -145,7 +145,7 @@ pub(crate) fn run_alongside(image: &str, mut testargs: libtest_mimic::Arguments)
         Trial::test("Install and verify selinux state", move || {
             let sh = &xshell::Shell::new()?;
             reset_root(sh, image)?;
-            cmd!(sh, "sudo {BASE_ARGS...} {target_args...} {image} bootc install to-existing-root --acknowledge-destructive {generic_inst_args...}").run()?;
+            cmd!(sh, "sudo {BASE_ARGS...} {image} bootc install to-existing-root --acknowledge-destructive {generic_inst_args...}").run()?;
             generic_post_install_verification()?;
             let root = &Dir::open_ambient_dir("/ostree", cap_std::ambient_authority()).unwrap();
             let mut path = PathBuf::from(".");
@@ -155,7 +155,7 @@ pub(crate) fn run_alongside(image: &str, mut testargs: libtest_mimic::Arguments)
         Trial::test("Install to non-default stateroot", move || {
             let sh = &xshell::Shell::new()?;
             reset_root(sh, image)?;
-            cmd!(sh, "sudo {BASE_ARGS...} {target_args...} {image} bootc install to-existing-root --stateroot {NON_DEFAULT_STATEROOT} --acknowledge-destructive {generic_inst_args...}").run()?;
+            cmd!(sh, "sudo {BASE_ARGS...} {image} bootc install to-existing-root --stateroot {NON_DEFAULT_STATEROOT} --acknowledge-destructive {generic_inst_args...}").run()?;
             generic_post_install_verification()?;
             assert!(
                 Utf8Path::new(&format!("/ostree/deploy/{NON_DEFAULT_STATEROOT}")).try_exists()?
@@ -167,7 +167,7 @@ pub(crate) fn run_alongside(image: &str, mut testargs: libtest_mimic::Arguments)
             reset_root(sh, image)?;
             let empty = sh.create_temp_dir()?;
             let empty = empty.path().to_str().unwrap();
-            cmd!(sh, "sudo {BASE_ARGS...} {target_args...} -v {empty}:/usr/lib/bootc/install {image} bootc install to-existing-root {generic_inst_args...}").run()?;
+            cmd!(sh, "sudo {BASE_ARGS...} -v {empty}:/usr/lib/bootc/install {image} bootc install to-existing-root {generic_inst_args...}").run()?;
             generic_post_install_verification()?;
             Ok(())
         }),