Support create_directory paths being an existing mount (#547)

* Support create_directory paths being an existing mount

* Tidy up after install even on mounts

* Repair steam deck test

* Fixup some nits

.github/workflows/ci.yml

@@ -292,7 +292,6 @@ jobs:
           backtrace: full
           github-token: ${{ secrets.GITHUB_TOKEN }}
           planner: steam-deck
-          extra-args: --persistence /home/runner/.ci-test-nix-home
       - name: Initial uninstall (without a `nix run` first)
         run: sudo -E /nix/nix-installer uninstall
         env:
@@ -327,7 +326,6 @@ jobs:
           backtrace: full
           github-token: ${{ secrets.GITHUB_TOKEN }}
           planner: steam-deck
-          extra-args: --persistence /home/runner/.ci-test-nix-home
       - name: echo $PATH
         run: echo $PATH
       - name: Test `nix` with `$GITHUB_PATH`

nix/tests/vm-test/default.nix

@@ -96,8 +96,12 @@ let
           exit 1
         fi
 
-        if [ -d /nix ]; then
+        if [ -d /nix/store ]; then
-          echo "/nix exists after uninstall"
+          echo "/nix/store exists after uninstall"
+          exit 1
+        fi
+        if [ -d /nix/var ]; then
+          echo "/nix/var exists after uninstall"
           exit 1
         fi
 
@@ -173,6 +177,17 @@ let
       uninstall = installCases.install-default.uninstall;
       uninstallCheck = installCases.install-default.uninstallCheck;
     };
+    install-bind-mounted-nix = {
+      preinstall = ''
+        sudo mkdir -p /nix
+        sudo mkdir -p /bind-mount-for-nix
+        sudo mount --bind /bind-mount-for-nix /nix
+      '';
+      install = installCases.install-default.install;
+      check = installCases.install-default.check;
+      uninstall = installCases.install-default.uninstall;
+      uninstallCheck = installCases.install-default.uninstallCheck;
+    };
   };
   cureSelfCases = {
     cure-self-linux-working = {

src/action/base/create_directory.rs

@@ -3,11 +3,13 @@ use std::path::{Path, PathBuf};
 
 use nix::unistd::{chown, Group, User};
 
-use tokio::fs::{create_dir, remove_dir_all};
+use tokio::fs::{create_dir, remove_dir_all, remove_file};
+use tokio::process::Command;
 use tracing::{span, Span};
 
 use crate::action::{Action, ActionDescription, ActionErrorKind, ActionState};
 use crate::action::{ActionError, StatefulAction};
+use crate::execute_command;
 
 /** Create a directory at the given location, optionally with an owning user, group, and mode.
 
@@ -20,6 +22,7 @@ pub struct CreateDirectory {
     user: Option<String>,
     group: Option<String>,
     mode: Option<u32>,
+    is_mountpoint: bool,
     force_prune_on_revert: bool,
 }
 
@@ -36,6 +39,7 @@ impl CreateDirectory {
         let user = user.into();
         let group = group.into();
         let mode = mode.into();
+        let mut is_mountpoint = false;
 
         let action_state = if path.exists() {
             let metadata = tokio::fs::metadata(&path)
@@ -84,7 +88,13 @@ impl CreateDirectory {
                 }
             }
 
-            tracing::debug!("Creating directory `{}` already complete", path.display(),);
+            // Is it a mountpoint?
+            is_mountpoint = path_is_mountpoint(&path).await.map_err(Self::error)?;
+            tracing::debug!(
+                is_mountpoint,
+                "Creating directory `{}` already complete",
+                path.display(),
+            );
             ActionState::Completed
         } else {
             ActionState::Uncompleted
@@ -96,6 +106,7 @@ impl CreateDirectory {
                 user,
                 group,
                 mode,
+                is_mountpoint,
                 force_prune_on_revert,
             },
             state: action_state,
@@ -137,9 +148,15 @@ impl Action for CreateDirectory {
             user,
             group,
             mode,
+            is_mountpoint, // If `is_mountpoint = true` the `ActionState` should be completed.
             force_prune_on_revert: _,
         } = self;
 
+        if *is_mountpoint {
+            // A `/nix` mount exists, we don't need to do anything.
+            return Ok(());
+        }
+
         let gid = if let Some(group) = group {
             Some(
                 Group::from_name(group.as_str())
@@ -189,20 +206,28 @@ impl Action for CreateDirectory {
             user: _,
             group: _,
             mode: _,
+            is_mountpoint,
             force_prune_on_revert,
         } = &self;
-        vec![ActionDescription::new(
+        match (is_mountpoint, force_prune_on_revert) {
-            format!(
+            (true, true) => vec![ActionDescription::new(
-                "Remove the directory `{}`{}",
+                format!("Clean contents of mountpoint `{}`", path.display(),),
-                path.display(),
+                vec![],
-                if *force_prune_on_revert {
+            )],
-                    ""
+            (true, false) => vec![],
-                } else {
+            (false, _) => vec![ActionDescription::new(
-                    " if no other contents exists"
+                format!(
-                }
+                    "Remove the directory `{}`{}",
-            ),
+                    path.display(),
-            vec![],
+                    if *force_prune_on_revert {
-        )]
+                        ""
+                    } else {
+                        " if no other contents exists"
+                    }
+                ),
+                vec![],
+            )],
+        }
     }
 
     #[tracing::instrument(level = "debug", skip_all)]
@@ -212,22 +237,50 @@ impl Action for CreateDirectory {
             user: _,
             group: _,
             mode: _,
+            is_mountpoint,
             force_prune_on_revert,
         } = self;
 
-        let is_empty = path
+        let contents = path
             .read_dir()
             .map_err(|e| ActionErrorKind::Read(path.clone(), e))
             .map_err(Self::error)?
-            .next()
+            .collect::<Vec<_>>();
-            .is_none();
+        let is_empty = contents.is_empty();
 
-        match (is_empty, force_prune_on_revert) {
+        match (is_mountpoint, is_empty, force_prune_on_revert) {
-            (true, _) | (false, true) => remove_dir_all(path.clone())
+            (true, _, true) => {
+                tracing::debug!("Cleaning mountpoint `{}`", path.display());
+                for child_path in contents {
+                    let child_path = child_path
+                        .map_err(|e| ActionErrorKind::ReadDir(path.clone(), e))
+                        .map_err(Self::error)?;
+                    let child_path_path = child_path.path();
+                    let child_path_type = child_path
+                        .file_type()
+                        .map_err(|e| ActionErrorKind::GettingMetadata(child_path_path.clone(), e))
+                        .map_err(Self::error)?;
+                    if child_path_type.is_dir() {
+                        remove_dir_all(child_path_path.clone())
+                            .await
+                            .map_err(|e| ActionErrorKind::Remove(path.clone(), e))
+                            .map_err(Self::error)?
+                    } else {
+                        remove_file(child_path_path)
+                            .await
+                            .map_err(|e| ActionErrorKind::Remove(path.clone(), e))
+                            .map_err(Self::error)?
+                    }
+                }
+            },
+            (true, _, false) => {
+                tracing::debug!("Not cleaning mountpoint `{}`", path.display());
+            },
+            (false, true, _) | (false, false, true) => remove_dir_all(path.clone())
                 .await
                 .map_err(|e| ActionErrorKind::Remove(path.clone(), e))
                 .map_err(Self::error)?,
-            (false, false) => {
+            (false, false, false) => {
                 tracing::debug!("Not removing `{}`, the folder is not empty", path.display());
             },
         };
@@ -236,6 +289,53 @@ impl Action for CreateDirectory {
     }
 }
 
+// There are cleaner ways of doing this (eg `systemctl status $PATH`) however we need a widely supported way.
+async fn path_is_mountpoint(path: &Path) -> Result<bool, ActionErrorKind> {
+    let path_str = match path.to_str() {
+        Some(path_str) => path_str,
+        None => return Err(ActionErrorKind::PathNoneString(path.to_path_buf())),
+    };
+
+    let mut mount_command = Command::new("mount");
+    mount_command.process_group(0);
+
+    #[cfg(target_os = "macos")]
+    mount_command.arg("-d"); // `-d` means `--dry-run`
+    #[cfg(target_os = "linux")]
+    mount_command.arg("-f"); // `-f` means `--fake` not `--force`
+
+    let output = execute_command(&mut mount_command).await?;
+    let output_string = String::from_utf8(output.stdout).map_err(ActionErrorKind::FromUtf8)?;
+
+    for line in output_string.lines() {
+        let mut line_splitter = line.split(" on ");
+        match line_splitter.next() {
+            Some(_device) => (),
+            None => continue,
+        }
+        let destination_and_options = match line_splitter.next() {
+            Some(destination_and_options) => destination_and_options,
+            None => continue,
+        };
+        // Each line on Linux looks like `portal on /run/user/1000/doc type fuse.portal (rw,nosuid,nodev,relatime,user_id=1000,group_id=100)`
+        #[cfg(target_os = "linux")]
+        let split_token = "type";
+        // Each line on MacOS looks like `/dev/disk3s6 on /System/Volumes/VM (apfs, local, noexec, journaled, noatime, nobrowse)`
+        #[cfg(target_os = "macos")]
+        let split_token = "(";
+
+        if let Some(mount_path) = destination_and_options.rsplit(split_token).last() {
+            let trimmed = mount_path.trim();
+            if trimmed == path_str {
+                tracing::trace!("Found mountpoint for `{mount_path}`");
+                return Ok(true);
+            }
+        }
+    }
+
+    Ok(false)
+}
+
 #[cfg(test)]
 mod test {
     use super::*;

src/action/common/create_nix_tree.rs

@@ -36,7 +36,7 @@ impl CreateNixTree {
         for path in PATHS {
             // We use `create_dir` over `create_dir_all` to ensure we always set permissions right
             create_directories.push(
-                CreateDirectory::plan(path, String::from("root"), None, 0o0755, false)
+                CreateDirectory::plan(path, String::from("root"), None, 0o0755, true)
                     .await
                     .map_err(Self::error)?,
             )

src/action/mod.rs

@@ -525,6 +525,8 @@ pub enum ActionErrorKind {
         #[from]
         std::string::FromUtf8Error,
     ),
+    #[error("Path `{}` could not be converted to valid UTF-8 string", .0.display())]
+    PathNoneString(std::path::PathBuf),
     /// A MacOS (Darwin) plist related error
     #[error(transparent)]
     Plist(#[from] plist::Error),

tests/fixtures/linux/linux.json

@@ -8,6 +8,7 @@
         "user": null,
         "group": null,
         "mode": 493,
+        "is_mountpoint": true,
         "force_prune_on_revert": true
       },
       "state": "Uncompleted"
@@ -41,6 +42,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -51,6 +53,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -61,6 +64,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -71,6 +75,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -81,6 +86,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -91,6 +97,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -101,6 +108,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -111,6 +119,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -121,6 +130,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -131,6 +141,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -141,6 +152,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -151,6 +163,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -161,6 +174,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -221,6 +235,7 @@
                   "user": null,
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Completed"
@@ -294,6 +309,7 @@
                 "user": null,
                 "group": null,
                 "mode": 493,
+                "is_mountpoint": true,
                 "force_prune_on_revert": false
               },
               "state": "Uncompleted"

tests/fixtures/linux/steam-deck.json

@@ -8,6 +8,7 @@
         "user": null,
         "group": null,
         "mode": 493,
+        "is_mountpoint": true,
         "force_prune_on_revert": true
       },
       "state": "Uncompleted"
@@ -85,6 +86,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -95,6 +97,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -105,6 +108,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -115,6 +119,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -125,6 +130,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -135,6 +141,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -145,6 +152,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -155,6 +163,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -165,6 +174,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -175,6 +185,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -185,6 +196,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -195,6 +207,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -205,6 +218,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -315,6 +329,7 @@
                 "user": null,
                 "group": null,
                 "mode": 493,
+                "is_mountpoint": true,
                 "force_prune_on_revert": false
               },
               "state": "Uncompleted"

tests/fixtures/macos/macos.json

@@ -110,6 +110,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -120,6 +121,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -130,6 +132,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -140,6 +143,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -150,6 +154,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -160,6 +165,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -170,6 +176,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -180,6 +187,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -190,6 +198,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -200,6 +209,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -210,6 +220,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -220,6 +231,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -230,6 +242,7 @@
                   "user": "root",
                   "group": null,
                   "mode": 493,
+                  "is_mountpoint": true,
                   "force_prune_on_revert": false
                 },
                 "state": "Uncompleted"
@@ -350,6 +363,7 @@
                 "user": null,
                 "group": null,
                 "mode": 493,
+                "is_mountpoint": true,
                 "force_prune_on_revert": false
               },
               "state": "Uncompleted"