generator: Conditinally enable bootc-status units

Right now this service fails in `bcvk run-ephemeral`, but
also likely fails in any non-bootc system that has `subscription-manager`
installed.

A problem is that dependencies of units are started even
if the dependee has a condition that disables it.

This basically the target and path depend on `/run/ostree-booted`
being present (which yes, won't work for composefs...)

Tests: Covered by extant `012-test-unit-status.nu`

Signed-off-by: Colin Walters <[email protected]>

Author: cgwalters

Makefile

@@ -32,9 +32,6 @@ install:
 	  fi; \
 	  done
 	install -D -m 0644 -t $(DESTDIR)/$(prefix)/lib/systemd/system systemd/*.service systemd/*.timer systemd/*.path systemd/*.target
-	install -d -m 0755 $(DESTDIR)/$(prefix)/lib/systemd/system/multi-user.target.wants
-	ln -s ../bootc-status-updated.path $(DESTDIR)/$(prefix)/lib/systemd/system/multi-user.target.wants/bootc-status-updated.path
-	ln -s ../bootc-status-updated-onboot.target $(DESTDIR)/$(prefix)/lib/systemd/system/multi-user.target.wants/bootc-status-updated-onboot.target
 	install -D -m 0644 -t $(DESTDIR)/$(prefix)/share/doc/bootc/baseimage/base/usr/lib/ostree/ baseimage/base/usr/lib/ostree/prepare-root.conf
 	install -d -m 755 $(DESTDIR)/$(prefix)/share/doc/bootc/baseimage/base/sysroot
 	cp -PfT baseimage/base/ostree $(DESTDIR)/$(prefix)/share/doc/bootc/baseimage/base/ostree 

crates/lib/src/generator.rs

@@ -1,12 +1,16 @@
 use std::io::BufRead;
 
 use anyhow::{Context, Result};
+use camino::Utf8PathBuf;
 use cap_std::fs::Dir;
 use cap_std_ext::{cap_std, dirext::CapStdExtDirExt};
 use fn_error_context::context;
-use ostree_ext::container_utils::is_ostree_booted_in;
+use ostree_ext::container_utils::{is_ostree_booted_in, OSTREE_BOOTED};
 use rustix::{fd::AsFd, fs::StatVfsMountFlags};
 
+const STATUS_ONBOOT_UNIT: &str = "bootc-status-updated-onboot.target";
+const STATUS_PATH_UNIT: &str = "bootc-status-updated.path";
+const MULTI_USER_TARGET: &str = "multi-user.target";
 const EDIT_UNIT: &str = "bootc-fstab-edit.service";
 const FSTAB_ANACONDA_STAMP: &str = "Created by anaconda";
 pub(crate) const BOOTC_EDITED_STAMP: &str = "Updated by bootc-fstab-edit.service";
@@ -47,9 +51,32 @@ pub(crate) fn fstab_generator_impl(root: &Dir, unit_dir: &Dir) -> Result<bool> {
     Ok(false)
 }
 
+/// Enable our units
+pub(crate) fn unit_enablement_impl(unit_dir: &Dir) -> Result<()> {
+    let wants = Utf8PathBuf::from(format!("{MULTI_USER_TARGET}.wants"));
+    unit_dir.create_dir_all(&wants)?;
+    let target = wants.join(STATUS_ONBOOT_UNIT);
+    unit_dir.symlink_contents(
+        format!("/usr/lib/systemd/system/{STATUS_ONBOOT_UNIT}"),
+        &target,
+    )?;
+    unit_dir.symlink_contents(
+        format!("/usr/lib/systemd/system/{STATUS_PATH_UNIT}"),
+        &target,
+    )?;
+    Ok(())
+}
+
 /// Main entrypoint for the generator
 pub(crate) fn generator(root: &Dir, unit_dir: &Dir) -> Result<()> {
-    // Right now we only do something if the root is a read-only overlayfs (a composefs really)
+    // Only run on ostree systems
+    if !root.try_exists(OSTREE_BOOTED)? {
+        return Ok(());
+    }
+
+    unit_enablement_impl(unit_dir)?;
+
+    // Also only run if the root is a read-only overlayfs (a composefs really)
     let st = rustix::fs::fstatfs(root.as_fd())?;
     if st.f_type != libc::OVERLAYFS_SUPER_MAGIC {
         tracing::trace!("Root is not overlayfs");
@@ -62,6 +89,7 @@ pub(crate) fn generator(root: &Dir, unit_dir: &Dir) -> Result<()> {
     }
     let updated = fstab_generator_impl(root, unit_dir)?;
     tracing::trace!("Generated fstab: {updated}");
+
     Ok(())
 }
 
@@ -109,6 +137,19 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn test_units() -> Result<()> {
+        let tempdir = fixture()?;
+        let unit_dir = &tempdir.open_dir("run/systemd/system")?;
+        unit_enablement_impl(&unit_dir).unwrap();
+        let r =
+            unit_dir.read_link_contents(format!("multi-user.target.wants/{STATUS_ONBOOT_UNIT}"))?;
+        let r: Utf8PathBuf = r.try_into().unwrap();
+        assert_eq!(r, format!("/usr/lib/systemd/system/{STATUS_ONBOOT_UNIT}"));
+        assert_eq!(unit_dir.entries()?.count(), 1);
+        Ok(())
+    }
+
     #[cfg(test)]
     mod test {
         use super::*;

systemd/bootc-status-updated-onboot.target

@@ -1,7 +1,4 @@
 [Unit]
-Description=Target for bootc status changes on boot
+Description=Bootc status trigger state sync
 Documentation=man:bootc-status-updated.target(8)
-ConditionPathExists=/run/ostree-booted
-
-[Install]
-WantedBy=multi-user.target
+After=sysinit.target

systemd/bootc-status-updated.path

@@ -1,11 +1,7 @@
 [Unit]
 Description=Monitor bootc for status changes
 Documentation=man:bootc-status-updated.path(8)
-ConditionPathExists=/run/ostree-booted
 
 [Path]
 PathChanged=/ostree/bootc
 Unit=bootc-status-updated.target
-
-[Install]
-WantedBy=multi-user.target