composefs/state: Copy /var from image to fresh installations

Signed-off-by: Chaser Huang <huangkangjing@gmail.com>

Author: chaserhkj

crates/lib/src/bootc_composefs/state.rs

@@ -107,6 +107,37 @@ pub(crate) fn copy_etc_to_state(
     cp_ret
 }
 
+/// Mounts an EROFS image and copies the pristine /var to the deployment's /var
+#[context("Copying var")]
+pub(crate) fn copy_var_to_state(
+    sysroot_path: &Utf8PathBuf,
+    erofs_id: &String,
+    state_path: &Utf8PathBuf,
+) -> Result<()> {
+    let sysroot_fd = open(
+        sysroot_path.as_std_path(),
+        OFlags::PATH | OFlags::DIRECTORY | OFlags::CLOEXEC,
+        Mode::empty(),
+    )
+    .context("Opening sysroot")?;
+
+    let composefs_fd = bootc_initramfs_setup::mount_composefs_image(&sysroot_fd, &erofs_id, false)?;
+
+    let tempdir = TempMount::mount_fd(composefs_fd)?;
+
+    // TODO: Replace this with a function to cap_std_ext
+    let cp_ret = Command::new("cp")
+        .args([
+            "-a",
+            "--remove-destination",
+            &format!("{}/var/.", tempdir.dir.path().as_str()?),
+            &format!("{state_path}/var/."),
+        ])
+        .run_capture_stderr();
+
+    cp_ret
+}
+
 /// Adds or updates the provided key/value pairs in the .origin file of the deployment pointed to
 /// by the `deployment_id`
 fn add_update_in_origin(
@@ -237,6 +268,10 @@ pub(crate) async fn write_composefs_state(
     )
     .context("Failed to create symlink for /var")?;
 
+    if !staged {
+        copy_var_to_state(&root_path, &deployment_id.to_hex(), &state_path)?;
+    }
+
     let ImageReference {
         image: image_name,
         transport,