Add a rollback verb and rollbackQueued status

I'd really hoped to do something more declarative here, and
really flesh out the intersections with automated upgrades
and automated rollbacks.

But, this just exposes the simple primitive, equivalent
to `rpm-ostree rollback`.

Signed-off-by: Colin Walters <walters@verbum.org>

lib/src/cli.rs

@@ -89,6 +89,10 @@ pub(crate) struct SwitchOpts {
     pub(crate) target: String,
 }
 
+/// Options controlling rollback
+#[derive(Debug, Parser, PartialEq, Eq)]
+pub(crate) struct RollbackOpts {}
+
 /// Perform an edit operation
 #[derive(Debug, Parser, PartialEq, Eq)]
 pub(crate) struct EditOpts {
@@ -214,6 +218,18 @@ pub(crate) enum Opt {
     /// This operates in a very similar fashion to `upgrade`, but changes the container image reference
     /// instead.
     Switch(SwitchOpts),
+    /// Change the bootloader entry ordering; the deployment under `rollback` will be queued for the next boot,
+    /// and the current will become rollback.  If there is a `staged` entry (an unapplied, queued upgrade)
+    /// then it will be discarded.
+    ///
+    /// Note that absent any additional control logic, if there is an active agent doing automated upgrades
+    /// (such as the default `bootc-fetch-apply-updates.timer` and associated `.service`) the
+    /// change here may be reverted.  It's recommended to only use this in concert with an agent that
+    /// is in active control.
+    ///
+    /// A systemd journal message will be logged with `MESSAGE_ID=26f3b1eb24464d12aa5e7b544a6b5468` in
+    /// order to detect a rollback invocation.
+    Rollback(RollbackOpts),
     /// Apply full changes to the host specification.
     ///
     /// This command operates very similarly to `kubectl apply`; if invoked interactively,
@@ -500,6 +516,14 @@ async fn switch(opts: SwitchOpts) -> Result<()> {
     Ok(())
 }
 
+/// Implementation of the `bootc rollback` CLI command.
+#[context("Rollback")]
+async fn rollback(_opts: RollbackOpts) -> Result<()> {
+    prepare_for_write().await?;
+    let sysroot = &get_locked_sysroot().await?;
+    crate::deploy::rollback(sysroot).await
+}
+
 /// Implementation of the `bootc edit` CLI command.
 #[context("Editing spec")]
 async fn edit(opts: EditOpts) -> Result<()> {
@@ -586,6 +610,7 @@ async fn run_from_opt(opt: Opt) -> Result<()> {
     match opt {
         Opt::Upgrade(opts) => upgrade(opts).await,
         Opt::Switch(opts) => switch(opts).await,
+        Opt::Rollback(opts) => rollback(opts).await,
         Opt::Edit(opts) => edit(opts).await,
         Opt::UsrOverlay => usroverlay().await,
         #[cfg(feature = "install")]

lib/src/deploy.rs

@@ -5,7 +5,7 @@
 use std::io::{BufRead, Write};
 
 use anyhow::Ok;
-use anyhow::{Context, Result};
+use anyhow::{anyhow, Context, Result};
 
 use cap_std::fs::{Dir, MetadataExt};
 use cap_std_ext::cap_std;
@@ -276,6 +276,53 @@ pub(crate) async fn stage(
     Ok(())
 }
 
+/// Implementation of rollback functionality
+pub(crate) async fn rollback(sysroot: &SysrootLock) -> Result<()> {
+    const ROLLBACK_JOURNAL_ID: &str = "26f3b1eb24464d12aa5e7b544a6b5468";
+    let repo = &sysroot.repo();
+    let (booted_deployment, deployments, host) = crate::status::get_status_require_booted(sysroot)?;
+    let reverting = host.status.rollback_queued;
+    if reverting {
+        println!("notice: Reverting queued rollback state");
+    }
+    let rollback_status = host
+        .status
+        .rollback
+        .ok_or_else(|| anyhow!("No rollback available"))?;
+    let rollback_image = rollback_status
+        .query_image(repo)?
+        .ok_or_else(|| anyhow!("Rollback is not container image based"))?;
+    let msg = format!("Rolling back to image: {}", rollback_image.manifest_digest);
+    libsystemd::logging::journal_send(
+        libsystemd::logging::Priority::Info,
+        &msg,
+        [
+            ("MESSAGE_ID", ROLLBACK_JOURNAL_ID),
+            ("BOOTC_MANIFEST_DIGEST", &rollback_image.manifest_digest),
+        ]
+        .into_iter(),
+    )?;
+    // SAFETY: If there's a rollback status, then there's a deployment
+    let rollback_deployment = deployments.rollback.expect("rollback deployment");
+    let new_deployments = if reverting {
+        [booted_deployment, rollback_deployment]
+    } else {
+        [rollback_deployment, booted_deployment]
+    };
+    let new_deployments = new_deployments
+        .into_iter()
+        .chain(deployments.other)
+        .collect::<Vec<_>>();
+    tracing::debug!("Writing new deployments: {new_deployments:?}");
+    sysroot.write_deployments(&new_deployments, gio::Cancellable::NONE)?;
+    if reverting {
+        println!("Next boot: current deployment");
+    } else {
+        println!("Next boot: rollback deployment");
+    }
+    Ok(())
+}
+
 fn find_newest_deployment_name(deploysdir: &Dir) -> Result<String> {
     let mut dirs = Vec::new();
     for ent in deploysdir.entries()? {

lib/src/spec.rs

@@ -121,6 +121,8 @@ pub struct HostStatus {
     pub booted: Option<BootEntry>,
     /// The previously booted image
     pub rollback: Option<BootEntry>,
+    /// Set to true if the rollback entry is queued for the next boot.
+    pub rollback_queued: bool,
 
     /// The detected type of system
     #[serde(rename = "type")]

lib/src/status.rs

@@ -224,11 +224,17 @@ pub(crate) fn get_status(
         .iter()
         .position(|d| d.is_staged())
         .map(|i| related_deployments.remove(i).unwrap());
+    tracing::debug!("Staged: {staged:?}");
     // Filter out the booted, the caller already found that
     if let Some(booted) = booted_deployment.as_ref() {
         related_deployments.retain(|f| !f.equal(booted));
     }
     let rollback = related_deployments.pop_front();
+    let rollback_queued = match (booted_deployment.as_ref(), rollback.as_ref()) {
+        (Some(booted), Some(rollback)) => rollback.index() < booted.index(),
+        _ => false,
+    };
+    tracing::debug!("Rollback queued={rollback_queued:?}");
     let other = {
         related_deployments.extend(other_deployments);
         related_deployments
@@ -281,6 +287,7 @@ pub(crate) fn get_status(
         staged,
         booted,
         rollback,
+        rollback_queued,
         ty,
     };
     Ok((deployments, host))

tests/integration/playbooks/rollback.yaml

@@ -6,8 +6,8 @@
     failed_counter: "0"
 
   tasks:
-    - name: rpm-ostree rollback
-      command: rpm-ostree rollback
+    - name: bootc rollback
+      command: bootc rollback
       become: true
 
     - name: Reboot to deploy new system