cli: Add container inspect

Prints JSON of container metadata/attributes of interest.

For now this just renders out the kargs embedded in the container
under the kargs.d drop-in.  Future ideas for enhancements would be to
include kernel version and whether or not the image uses a UKI.

Closes: #1827
Signed-off-by: John Eckersberg <[email protected]>

Author: jeckersb

crates/lib/src/cli.rs

@@ -295,6 +295,12 @@ pub(crate) enum InstallOpts {
 /// Subcommands which can be executed as part of a container build.
 #[derive(Debug, clap::Subcommand, PartialEq, Eq)]
 pub(crate) enum ContainerOpts {
+    /// Output JSON to stdout containing the container image metadata.
+    Inspect {
+        /// Operate on the provided rootfs.
+        #[clap(long, default_value = "/")]
+        rootfs: Utf8PathBuf,
+    },
     /// Perform relatively inexpensive static analysis checks as part of a container
     /// build.
     ///
@@ -1345,6 +1351,14 @@ async fn run_from_opt(opt: Opt) -> Result<()> {
             }
         }
         Opt::Container(opts) => match opts {
+            ContainerOpts::Inspect { rootfs } => {
+                let root = &Dir::open_ambient_dir(&rootfs, cap_std::ambient_authority())?;
+                let kargs = crate::bootc_kargs::get_kargs_in_root(root, std::env::consts::ARCH)?;
+                let kargs: Vec<String> = kargs.iter_str().map(|s| s.to_owned()).collect();
+                let inspect = crate::spec::ContainerInspect { kargs };
+                serde_json::to_writer_pretty(std::io::stdout().lock(), &inspect)?;
+                Ok(())
+            }
             ContainerOpts::Lint {
                 rootfs,
                 fatal_warnings,

crates/lib/src/spec.rs

@@ -275,6 +275,14 @@ pub(crate) struct DeploymentEntry<'a> {
     pub(crate) pinned: bool,
 }
 
+/// The result of a `bootc container inspect` command.
+#[derive(Debug, Serialize)]
+#[serde(rename_all = "kebab-case")]
+pub(crate) struct ContainerInspect {
+    /// Kernel arguments embedded in the container image.
+    pub(crate) kargs: Vec<String>,
+}
+
 impl Host {
     /// Create a new host
     pub fn new(spec: HostSpec) -> Self {

crates/tests-integration/src/container.rs

@@ -21,6 +21,20 @@ pub(crate) fn test_bootc_status() -> Result<()> {
     Ok(())
 }
 
+pub(crate) fn test_bootc_container_inspect() -> Result<()> {
+    let sh = Shell::new()?;
+    let inspect: serde_json::Value =
+        serde_json::from_str(&cmd!(sh, "bootc container inspect").read()?)?;
+
+    // check kargs processing
+    let kargs = inspect.get("kargs").unwrap().as_array().unwrap();
+    assert!(kargs.iter().any(|arg| arg == "kargsd-test=1"));
+    assert!(kargs.iter().any(|arg| arg == "kargsd-othertest=2"));
+    assert!(kargs.iter().any(|arg| arg == "testing-kargsd=3"));
+
+    Ok(())
+}
+
 pub(crate) fn test_bootc_upgrade() -> Result<()> {
     for c in ["upgrade", "update"] {
         let o = Command::new("bootc").arg(c).output()?;
@@ -120,6 +134,7 @@ pub(crate) fn run(testargs: libtest_mimic::Arguments) -> Result<()> {
         new_test("install config", test_bootc_install_config),
         new_test("printconfig --all", test_bootc_install_config_all),
         new_test("status", test_bootc_status),
+        new_test("container inspect", test_bootc_container_inspect),
         new_test("system-reinstall --help", test_system_reinstall_help),
     ];