Import GRUB static migration code

Makefile

@@ -43,6 +43,7 @@ install-grub-static:
 
 install-systemd-unit:
 	install -m 644 -D -t "${DESTDIR}$(PREFIX)/lib/systemd/system/" contrib/packaging/bootloader-update.service
+	install -m 644 -D -t "${DESTDIR}$(PREFIX)/lib/systemd/system/" contrib/packaging/bootupd-static-grub-migration.service
 
 bin-archive:
 	rm target/inst -rf

contrib/packaging/bootupd-static-grub-migration.service

@@ -0,0 +1,17 @@
+[Unit]
+Description=bootupd static GRUB config migration
+Documentation=https://github.com/coreos/bootupd
+ConditionPathExists=!/boot/.bootupd-static-migration-complete
+RequiresMountsFor=/sysroot /boot
+# Only run after a successful bootloader update
+After=bootloader-update.service
+Requires=bootloader-update.service
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/bootupctl migrate
+RemainAfterExit=yes
+MountFlags=slave
+
+[Install]
+WantedBy=multi-user.target

contrib/packaging/bootupd.spec

@@ -36,6 +36,7 @@ BuildRequires: systemd-rpm-macros
 %{_libexecdir}/bootupd
 %{_prefix}/lib/bootupd/grub2-static/
 %{_unitdir}/bootloader-update.service
+%{_unitdir}/bootupd-static-grub-migration.service
 
 %prep
 %autosetup -n %{crate}-%{version} -p1 -Sgit

src/bootupd.rs

@@ -9,10 +9,12 @@ use crate::model::{ComponentStatus, ComponentUpdatable, ContentMetadata, SavedSt
 use crate::util;
 use anyhow::{anyhow, Context, Result};
 use clap::crate_version;
+use fn_error_context::context;
 use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
 use std::collections::BTreeMap;
-use std::path::Path;
+use std::fs::{self, File};
+use std::path::{Path, PathBuf};
 
 pub(crate) enum ConfigMode {
     None,
@@ -489,6 +491,127 @@ pub(crate) fn client_run_validate() -> Result<()> {
     Ok(())
 }
 
+#[context("Migrating to static grub config")]
+pub(crate) fn client_run_migrate() -> Result<()> {
+    // Used to condition execution of this unit at the systemd level
+    let stamp_file = "/boot/.bootupd-static-migration-complete";
+
+    // Did we already complete the migration?
+    let mut ostree_cmd = std::process::Command::new("ostree");
+    let result = ostree_cmd
+        .args([
+            "config",
+            "--repo=/sysroot/ostree/repo",
+            "get",
+            "sysroot.bootloader",
+        ])
+        .output()
+        .context("Querying ostree sysroot.bootloader")?;
+    if !result.status.success() {
+        // ostree will exit with a non zero return code if the key does not exists
+        println!("ostree repo 'sysroot.bootloader' config option not set yet.");
+    } else {
+        let bootloader = String::from_utf8(result.stdout)
+            .with_context(|| "decoding as UTF-8 output of ostree command")?;
+        if bootloader.trim_end() == "none" {
+            println!("ostree repo 'sysroot.bootloader' config option already set to 'none'.");
+            println!("Assuming that the migration is already complete.");
+            File::create(stamp_file)?;
+            return Ok(());
+        }
+        println!(
+            "ostree repo 'sysroot.bootloader' config currently set to: {}",
+            bootloader.trim_end()
+        );
+    }
+
+    // Remount /boot read write just for this unit (we are called in a slave mount namespace by systemd)
+    ensure_writable_boot()?;
+
+    let grub_config_dir = PathBuf::from("/boot/grub2");
+    let dirfd = openat::Dir::open(&grub_config_dir).context("Opening /boot/grub2")?;
+
+    // Migrate /boot/grub2/grub.cfg to a static GRUB config if it is a symlink
+    let grub_config_filename = PathBuf::from("/boot/grub2/grub.cfg");
+    match dirfd.read_link("grub.cfg") {
+        Err(_) => {
+            println!(
+                "'{}' is not a symlink. Nothing to migrate.",
+                grub_config_filename.display()
+            );
+        }
+        Ok(path) => {
+            println!("Migrating to a static GRUB config...");
+
+            // Resolve symlink location
+            let mut current_config = grub_config_dir.clone();
+            current_config.push(path);
+
+            // Backup the current GRUB config which is hopefully working right now
+            let backup_config = PathBuf::from("/boot/grub2/grub.cfg.backup");
+            println!(
+                "Creating a backup of the current GRUB config '{}' in '{}'...",
+                current_config.display(),
+                backup_config.display()
+            );
+            fs::copy(&current_config, &backup_config).context("Failed to backup GRUB config")?;
+
+            // Copy it again alongside the current symlink
+            let current_config_copy = PathBuf::from("/boot/grub2/grub.cfg.current");
+            fs::copy(&current_config, &current_config_copy)
+                .context("Failed to copy the current GRUB config")?;
+
+            // Atomically exchange the configs
+            dirfd
+                .local_exchange("grub.cfg.current", "grub.cfg")
+                .context("Failed to exchange symlink with current GRUB config")?;
+
+            // Remove the now unused symlink (optional cleanup, ignore any failures)
+            _ = dirfd.remove_file("grub.cfg.current");
+
+            println!("GRUB config symlink successfully replaced with the current config.");
+        }
+    };
+
+    // If /etc/default/grub exists then we have to force the regeneration of the
+    // GRUB config to remove the ostree entries that duplicates the BLS ones
+    let grub_default = PathBuf::from("/etc/default/grub");
+    if grub_default.exists() {
+        println!("Marking bootloader as BLS capable...");
+        File::create("/boot/grub2/.grub2-blscfg-supported")
+            .context("Failed to mark bootloader as BLS capable")?;
+
+        println!("Regenerating GRUB config with only BLS configs...");
+        let status = std::process::Command::new("grub2-mkconfig")
+            .arg("-o")
+            .arg(grub_config_filename)
+            .status()?;
+        if !status.success() {
+            anyhow::bail!("Failed to regenerate GRUB config");
+        }
+    }
+
+    println!("Setting up 'sysroot.bootloader' to 'none' in ostree repo config...");
+    let status = std::process::Command::new("ostree")
+        .args([
+            "config",
+            "--repo=/sysroot/ostree/repo",
+            "set",
+            "sysroot.bootloader",
+            "none",
+        ])
+        .status()?;
+    if !status.success() {
+        anyhow::bail!("Failed to set 'sysroot.bootloader' to 'none' in ostree repo config");
+    }
+
+    // Migration complete, let's write the stamp file
+    File::create(stamp_file)?;
+
+    println!("Static GRUB config migration completed successfully!");
+    Ok(())
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;

src/cli/bootupctl.rs

@@ -58,6 +58,8 @@ pub enum CtlVerb {
     AdoptAndUpdate,
     #[clap(name = "validate", about = "Validate system state")]
     Validate,
+    #[clap(name = "migrate", about = "Migrate a system to static a GRUB config")]
+    Migrate,
 }
 
 #[derive(Debug, Parser)]
@@ -95,6 +97,7 @@ impl CtlCommand {
             CtlVerb::Backend(CtlBackend::Install(opts)) => {
                 super::bootupd::DCommand::run_install(opts)
             }
+            CtlVerb::Migrate => Self::run_migrate(),
         }
     }
 
@@ -135,6 +138,12 @@ impl CtlCommand {
         ensure_running_in_systemd()?;
         bootupd::client_run_validate()
     }
+
+    /// Runner for `migrate` verb.
+    fn run_migrate() -> Result<()> {
+        ensure_running_in_systemd()?;
+        bootupd::client_run_migrate()
+    }
 }
 
 /// Checks if the current process is (apparently at least)