install: Add kargs to installation config

ci/Dockerfile.fcos

@@ -7,4 +7,5 @@ RUN make test-bin-archive
 
 FROM quay.io/fedora/fedora-coreos:testing-devel
 COPY --from=builder /src/target/bootc.tar.zst /tmp
+COPY ci/usr usr
 RUN tar -xvf /tmp/bootc.tar.zst && ostree container commit 

ci/usr/lib/bootc/install/50-test-kargs.toml

@@ -0,0 +1,2 @@
+[install]
+kargs = ["localtestkarg=somevalue", "otherlocalkarg=42"]

docs/install.md

@@ -96,21 +96,32 @@ in that case you will need to specify `--skip-fetch-check`.
 
 ### Operating system install configuration required
 
-The container image **MUST** define its default install configuration.  For example,
-create `/usr/lib/bootc/install/00-exampleos.toml` with the contents:
+The container image **MUST** define its default install configuration.  A key choice
+that bootc by default leaves up to the operating system image is the root filesystem
+type.
+
+To enable `bootc install` as part of your OS/distribution base image,
+create a file named `/usr/lib/bootc/install/00-<osname>.toml` with the contents of the form:
 
 ```toml
 [install]
 root-fs-type = "xfs"
 ```
 
-At the current time, `root-fs-type` is the only available configuration option, and it **MUST** be set.
+The `root-fs-type` value **MUST** be set.
 
 Configuration files found in this directory will be merged, with higher alphanumeric values
 taking precedence.  If for example you are building a derived container image from the above OS,
 you could create a `50-myos.toml`  that sets `root-fs-type = "btrfs"` which will override the
 prior setting.
 
+Other available options, also under the `[install]` section:
+
+`kargs`: This allows setting kernel arguments which apply only at the time of `bootc install`.
+This option is particularly useful when creating derived/layered images; for example, a cloud
+image may want to have its default `console=` set, in contrast with a default base image.
+The values in this field are space separated.
+
 ## Installing an "unconfigured" image
 
 The bootc project aims to support generic/general-purpose operating

lib/Cargo.toml

@@ -34,6 +34,7 @@ regex = "1.7.1"
 rustix = { "version" = "0.38", features = ["thread", "fs", "system", "process"] }
 schemars = { version = "0.8.6", features = ["chrono"] }
 serde = { features = ["derive"], version = "1.0.125" }
+serde_ignored = "0.1.9"
 serde_json = "1.0.64"
 serde_yaml = "0.9.17"
 serde_with = ">= 1.9.4, < 2"

lib/src/install.rs

@@ -381,7 +381,10 @@ pub(crate) mod config {
     #[derive(Debug, Clone, Serialize, Deserialize, Default)]
     #[serde(rename = "install", rename_all = "kebab-case", deny_unknown_fields)]
     pub(crate) struct InstallConfiguration {
+        /// Root filesystem type
         pub(crate) root_fs_type: Option<super::baseline::Filesystem>,
+        /// Kernel arguments, applied at installation time
+        pub(crate) kargs: Option<Vec<String>>,
     }
 
     impl InstallConfiguration {
@@ -392,7 +395,12 @@ pub(crate) mod config {
                     *s = Some(o);
                 }
             }
-            mergeopt(&mut self.root_fs_type, other.root_fs_type)
+            mergeopt(&mut self.root_fs_type, other.root_fs_type);
+            if let Some(other_kargs) = other.kargs {
+                self.kargs
+                    .get_or_insert_with(|| Default::default())
+                    .extend(other_kargs)
+            }
         }
     }
 
@@ -405,10 +413,18 @@ pub(crate) mod config {
         let mut config: Option<InstallConfiguration> = None;
         for (_name, path) in fragments {
             let buf = std::fs::read_to_string(&path)?;
-            let c: InstallConfigurationToplevel =
-                toml::from_str(&buf).with_context(|| format!("Parsing {path:?}"))?;
+            let mut unused = std::collections::HashSet::new();
+            let de = toml::Deserializer::new(&buf);
+            let c: InstallConfigurationToplevel = serde_ignored::deserialize(de, |path| {
+                unused.insert(path.to_string());
+            })
+            .with_context(|| format!("Parsing {path:?}"))?;
+            for key in unused {
+                eprintln!("warning: {path:?}: Unknown key {key}");
+            }
             if let Some(config) = config.as_mut() {
                 if let Some(install) = c.install {
+                    tracing::debug!("Merging install config: {install:?}");
                     config.merge(install);
                 }
             } else {
@@ -434,10 +450,43 @@ root-fs-type = "xfs"
         let other = InstallConfigurationToplevel {
             install: Some(InstallConfiguration {
                 root_fs_type: Some(Filesystem::Ext4),
+                kargs: None,
             }),
         };
         install.merge(other.install.unwrap());
         assert_eq!(install.root_fs_type.unwrap(), Filesystem::Ext4);
+
+        let c: InstallConfigurationToplevel = toml::from_str(
+            r##"[install]
+root-fs-type = "ext4"
+kargs = ["console=ttyS0", "foo=bar"]
+"##,
+        )
+        .unwrap();
+        let mut install = c.install.unwrap();
+        assert_eq!(install.root_fs_type.unwrap(), Filesystem::Ext4);
+        let other = InstallConfigurationToplevel {
+            install: Some(InstallConfiguration {
+                root_fs_type: None,
+                kargs: Some(
+                    ["console=tty0", "nosmt"]
+                        .into_iter()
+                        .map(ToOwned::to_owned)
+                        .collect(),
+                ),
+            }),
+        };
+        install.merge(other.install.unwrap());
+        assert_eq!(install.root_fs_type.unwrap(), Filesystem::Ext4);
+        assert_eq!(
+            install.kargs,
+            Some(
+                ["console=ttyS0", "foo=bar", "console=tty0", "nosmt"]
+                    .into_iter()
+                    .map(ToOwned::to_owned)
+                    .collect()
+            )
+        )
     }
 }
 

lib/src/install/baseline.rs

@@ -350,6 +350,14 @@ pub(crate) fn install_create_rootfs(
         .into_iter()
         .flatten()
         .chain([rootarg, RW_KARG.to_string(), bootarg].into_iter())
+        .chain(
+            state
+                .install_config
+                .kargs
+                .iter()
+                .flatten()
+                .map(ToOwned::to_owned),
+        )
         .collect::<Vec<_>>();
 
     mount::mount(&rootdev, &rootfs)?;

tests/kolainst/install

@@ -19,12 +19,24 @@ cd $(mktemp -d)
 
 case "${AUTOPKGTEST_REBOOT_MARK:-}" in
   "")
-    podman run --rm -ti --privileged --pid=host -v /usr/bin/bootc:/usr/bin/bootc ${IMAGE} bootc install --target-no-signature-verification --karg=foo=bar ${DEV}
+    mkdir -p ~/.config/containers
+    cp -a /etc/ostree/auth.json ~/.config/containers
+    mkdir -p usr/{lib,bin}
+    cp -a /usr/lib/bootc usr/lib
+    cp -a /usr/bin/bootc usr/bin
+    cat > Dockerfile << EOF
+    FROM ${IMAGE}
+    COPY usr usr
+EOF
+    podman build -t localhost/testimage .
+    podman run --rm -ti --privileged --pid=host --env RUST_LOG=error,bootc_lib::install=debug \
+      localhost/testimage bootc install --target-no-signature-verification --skip-fetch-check --karg=foo=bar ${DEV}
     # In theory we could e.g. wipe the bootloader setup on the primary disk, then reboot;
     # but for now let's just sanity test that the install command executes.
     lsblk ${DEV}
     mount /dev/vda3 /var/mnt
     grep foo=bar /var/mnt/loader/entries/*.conf
+    grep localtestkarg=somevalue /var/mnt/loader/entries/*.conf
     grep -Ee '^linux /boot/ostree' /var/mnt/loader/entries/*.conf
     umount /var/mnt
     echo "ok install"