WIP: Add support for --replace-mode=alongside for ostree target

Ironically our support for `--replace-mode=alongside` breaks
when we're targeting an already extant ostree host, because when
we first blow away the `/boot` directory, this means the ostree
stack loses its knowledge that we're in a booted deployment,
and will attempt to GC it...

ostreedev/ostree-rs-ext@8fa019b
is a key part of the fix for that.

However, a notable improvement we can do here is to grow this
whole thing into a real "factory reset" mode, and this will
be a compelling answer to
coreos/fedora-coreos-tracker#399

To implement this though we need to support configuring the
stateroot and not just hardcode `default`.

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

lib/src/install.rs

@@ -588,11 +588,17 @@ async fn initialize_ostree_root(state: &State, root_setup: &RootSetup) -> Result
 
     let stateroot = state.stateroot();
 
-    Task::new_and_run(
-        "Initializing ostree layout",
-        "ostree",
-        ["admin", "init-fs", "--modern", rootfs.as_str()],
-    )?;
+    let has_ostree = rootfs_dir.try_exists("ostree/repo")?;
+    if !has_ostree {
+        Task::new_and_run(
+            "Initializing ostree layout",
+            "ostree",
+            ["admin", "init-fs", "--modern", rootfs.as_str()],
+        )?;
+    } else {
+        println!("Reusing extant ostree layout");
+        let _ = crate::utils::open_dir_remount_rw(rootfs_dir, "sysroot".into())?;
+    }
 
     // And also label /boot AKA xbootldr, if it exists
     let bootdir = rootfs.join("boot");
@@ -617,9 +623,15 @@ async fn initialize_ostree_root(state: &State, root_setup: &RootSetup) -> Result
     let sysroot = ostree::Sysroot::new(Some(&gio::File::for_path(rootfs)));
     sysroot.load(cancellable)?;
 
-    sysroot
-        .init_osname(stateroot, cancellable)
-        .context("initializing stateroot")?;
+    let stateroot_exists = rootfs_dir.try_exists(format!("ostree/deploy/{stateroot}"))?;
+    if stateroot_exists {
+        anyhow::bail!("Cannot redeploy over extant stateroot {stateroot}");
+    } else {
+        Task::new("Initializing stateroot", "ostree")
+            .args(["admin", "os-init", stateroot, "--sysroot", "."])
+            .cwd(rootfs_dir)?
+            .run()?;
+    }
 
     let sysroot_dir = Dir::reopen_dir(&crate::utils::sysroot_fd(&sysroot))?;
 
@@ -740,6 +752,7 @@ async fn install_container(
     options.kargs = Some(kargs.as_slice());
     options.target_imgref = Some(&state.target_imgref);
     options.proxy_cfg = proxy_cfg;
+    options.no_clean = root_setup.has_ostree;
     let imgstate = crate::utils::async_task_with_spinner(
         "Deploying container image",
         ostree_container::deploy::deploy(&sysroot, stateroot, &src_imageref, Some(options)),
@@ -1511,7 +1524,8 @@ fn remove_all_in_dir_no_xdev(d: &Dir) -> Result<()> {
 
 #[context("Removing boot directory content")]
 fn clean_boot_directories(rootfs: &Dir) -> Result<()> {
-    let bootdir = rootfs.open_dir(BOOT).context("Opening /boot")?;
+    let bootdir =
+        crate::utils::open_dir_remount_rw(rootfs, BOOT.into()).context("Opening /boot")?;
     // This should not remove /boot/efi note.
     remove_all_in_dir_no_xdev(&bootdir)?;
     if ARCH_USES_EFI {

lib/src/utils.rs

@@ -5,7 +5,9 @@ use std::process::Command;
 use std::time::Duration;
 
 use anyhow::{Context, Result};
-use cap_std_ext::cap_std::fs::Dir;
+use camino::Utf8Path;
+use cap_std_ext::{cap_std::fs::Dir, prelude::CapStdExtCommandExt};
+use fn_error_context::context;
 use indicatif::HumanDuration;
 use libsystemd::logging::journal_print;
 use ostree::glib;
@@ -57,6 +59,30 @@ pub(crate) fn find_mount_option<'a>(
         .next()
 }
 
+/// Given a target directory, if it's a read-only mount, then remount it writable
+#[context("Opening {target} with writable mount")]
+pub(crate) fn open_dir_remount_rw(root: &Dir, target: &Utf8Path) -> Result<Dir> {
+    if ostree_ext::mountutil::is_mountpoint(root, target)?.unwrap_or_default() {
+        tracing::debug!("Target {target} is a mountpoint, remounting rw");
+        let st = Command::new("mount")
+            .args(["-o", "remount,rw", target.as_str()])
+            .cwd_dir(root.try_clone()?)
+            .status()?;
+        if !st.success() {
+            anyhow::bail!("Failed to remount: {st:?}");
+        }
+    }
+    root.open_dir(target).map_err(anyhow::Error::new)
+}
+
+/// Run a command in the host mount namespace
+#[allow(dead_code)]
+pub(crate) fn run_in_host_mountns(cmd: &str) -> Command {
+    let mut c = Command::new("nsenter");
+    c.args(["-m", "-t", "1", "--", cmd]);
+    c
+}
+
 pub(crate) fn spawn_editor(tmpf: &tempfile::NamedTempFile) -> Result<()> {
     let editor_variables = ["EDITOR"];
     // These roughly match https://github.com/systemd/systemd/blob/769ca9ab557b19ee9fb5c5106995506cace4c68f/src/shared/edit-util.c#L275