add auto_late_mounts, improve documentation

Signed-off-by: Zen <[email protected]>

Author: desultory

docs/configuration.md

@@ -245,8 +245,16 @@ Additional modules include:
 
 `mounts`: A dictionary containing entries for mounts, with their associated config.
 
+Mounts defined here are mounted before `init_main` is run. This cannot be used for mounts backed by LUKS, LVM, or MDRAID devices, because the backend will not be available when these mounts are attempted.
+
+> `mounts` can be automatically populated by configuring paths as list items in `auto_mounts`.
+
 `mounts.root` is predefined to have a destination of `/target_rootfs` and defines the root filesystem mount, used by `switch_root`.
 
+`late_mounts`: A dictionary containing entries for mounts that should be mounted after `init_main` is run.
+
+>  `late_mounts` can be automatically populated by configuring paths as list items in `auto_late_mounts`.
+
 Each mount has the following available parameters:
 
 * `type` (auto) Mount filesystem type.
@@ -285,6 +293,8 @@ label = "extra"
 
 Paths added to `auto_mounts` will be auto-configured to mount before `init_main` is run.
 
+Paths added to `auto_late_mounts` will be auto-configured to mount after `init_main` is run.  
+
 #### ugrd.fs.fakeudev
 
 This module is used to create fake udev entries for DM devices.

src/ugrd/fs/mounts.py

@@ -866,6 +866,14 @@ def autodetect_mounts(self) -> None:
         _autodetect_mount(self, mountpoint)
 
 
+@contains("auto_late_mounts", "Skipping auto late mounts, auto_late_mounts is empty.", log_level=10)
+@contains("hostonly", "Skipping late mount autodetection, hostonly mode is disabled.", log_level=30)
+def autodetect_late_mounts(self) -> None:
+    """Configured the late_mounts config for a device based on the host mount config."""
+    for mountpoint in self["auto_late_mounts"]:
+        _autodetect_mount(self, mountpoint, mount_class="late_mounts")
+
+
 def mount_base(self) -> list[str]:
     """Generates mount commands for the base mounts.
     Must be run before variables are used, as it creates the /run/ugrd directory.

src/ugrd/fs/mounts.toml

@@ -22,7 +22,7 @@ autodetect_init_mount = true
 
 [imports.build_enum]
 "ugrd.fs.mounts" = [ "get_mounts_info", "get_virtual_block_info", "get_blkid_info", "get_zpool_info",
-		     "autodetect_root", "autodetect_mounts", "autodetect_init_mount" ]
+		     "autodetect_root", "autodetect_mounts", "autodetect_late_mounts", "autodetect_init_mount" ]
 
 [imports.build_tasks]
 "ugrd.fs.mounts" = [ "export_mount_info" ]
@@ -58,6 +58,7 @@ mount_devpts = "bool"  # Whether or not to mount devpts
 run_dirs = "NoDupFlatList"  # A list of directories to be created under /run
 late_mounts = "dict"  # Like mounts, but run after the root is mounted
 auto_mounts = "NoDupFlatList"  # A list of mounts to be automatically added to the mounts list
+auto_late_mounts = "NoDupFlatList"  # A list of mounts to be automatically added to the late mounts list
 mount_timeout = "float"  # The time to wait between mount attempts
 mount_retries = "int"  # The number of times to re-attempt mounting the fstab, infinite if not set
 mount_cmd = "str"  # The mount command called by mount_root, can be overridden