service: exit and prevent restarts if booted into a container image

dist/systemd/system/zincati.service

@@ -21,6 +21,8 @@ Environment=ZINCATI_VERBOSITY="-v"
 Type=notify
 ExecStart=/usr/libexec/zincati agent ${ZINCATI_VERBOSITY}
 Restart=on-failure
+# This status signals a non-restartable condition
+RestartPreventExitStatus=7
 RestartSec=10s
 
 [Install]

src/main.rs

@@ -56,20 +56,27 @@ fn run() -> i32 {
     match cli_opts.run() {
         Ok(_) => libc::EXIT_SUCCESS,
         Err(e) => {
-            log_error_chain(e);
-            libc::EXIT_FAILURE
+            log_error_chain(&e);
+            if e.root_cause()
+                .downcast_ref::<crate::rpm_ostree::FatalError>()
+                .is_some()
+            {
+                7
+            } else {
+                libc::EXIT_FAILURE
+            }
         }
     }
 }
 
 /// Pretty-print a chain of errors, as a series of error-priority log messages.
-fn log_error_chain(err_chain: anyhow::Error) {
+fn log_error_chain(err_chain: &anyhow::Error) {
     let mut chain_iter = err_chain.chain();
     let top_err = match chain_iter.next() {
         Some(e) => e.to_string(),
         None => "(unspecified failure)".to_string(),
     };
-    log::error!("critical error: {}", top_err);
+    log::error!("error: {}", top_err);
     for err in chain_iter {
         log::error!(" -> {}", err);
     }

src/rpm_ostree/cli_status.rs

@@ -37,6 +37,18 @@ lazy_static::lazy_static! {
     )).unwrap();
 }
 
+/// An error which should not result in a retry/restart.
+#[derive(Debug, Clone)]
+pub struct FatalError(String);
+
+impl std::fmt::Display for FatalError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.0.fmt(f)
+    }
+}
+
+impl std::error::Error for FatalError {}
+
 /// JSON output from `rpm-ostree status --json`
 #[derive(Clone, Debug, Deserialize)]
 pub struct StatusJson {
@@ -48,6 +60,7 @@ pub struct StatusJson {
 #[serde(rename_all = "kebab-case")]
 pub struct DeploymentJson {
     booted: bool,
+    container_image_reference: Option<String>,
     base_checksum: Option<String>,
     #[serde(rename = "base-commit-meta")]
     base_metadata: BaseCommitMetaJson,
@@ -62,7 +75,7 @@ pub struct DeploymentJson {
 #[derive(Clone, Debug, Deserialize)]
 struct BaseCommitMetaJson {
     #[serde(rename = "fedora-coreos.stream")]
-    stream: String,
+    stream: Option<String>,
 }
 
 impl DeploymentJson {
@@ -85,12 +98,21 @@ impl DeploymentJson {
 
 /// Parse the booted deployment from status object.
 pub fn parse_booted(status: &StatusJson) -> Result<Release> {
-    let json = booted_json(status)?;
-    Ok(json.into_release())
+    let status = booted_json(status)?;
+    if let Some(img) = status.container_image_reference.as_ref() {
+        let msg = format!("Automatic updates disabled; booted into container image {img}");
+        crate::utils::update_unit_status(&msg);
+        return Err(anyhow::Error::new(FatalError(msg)));
+    }
+    Ok(status.into_release())
 }
 
 fn fedora_coreos_stream_from_deployment(deploy: &DeploymentJson) -> Result<String> {
-    let stream = deploy.base_metadata.stream.as_str();
+    let stream = deploy
+        .base_metadata
+        .stream
+        .as_ref()
+        .ok_or_else(|| anyhow!("Missing `fedora-coreos.stream` in commit metadata"))?;
     ensure!(!stream.is_empty(), "empty stream value");
     Ok(stream.to_string())
 }

src/rpm_ostree/mod.rs

@@ -1,7 +1,7 @@
 mod cli_deploy;
 mod cli_finalize;
 mod cli_status;
-pub use cli_status::{invoke_cli_status, parse_booted, parse_booted_updates_stream};
+pub use cli_status::{invoke_cli_status, parse_booted, parse_booted_updates_stream, FatalError};
 
 mod actor;
 pub use actor::{