Implementing device_aliases as described in docs (#945)

Implement missing device_aliases feature

The device_aliases key has been documented as part of disk_setup for
years, however the feature was never implemented. This implements the
feature as documented allowing usercfg (rather than dsconfig) to create
a mapping of device names.

This is not to be confused with disk_aliases, a very similar map but
existing solely for use by datasources.

LP: #1867532

2 files changed, 23 insertions, 7 deletions

diff --git a/cloudinit/config/cc_disk_setup.py b/cloudinit/config/cc_disk_setup.py
index 22af3813..3ec49ca5 100644
--- a/cloudinit/config/cc_disk_setup.py
+++ b/cloudinit/config/cc_disk_setup.py
@@ -125,9 +125,15 @@ def handle(_name, cfg, cloud, log, _args):
     See doc/examples/cloud-config-disk-setup.txt for documentation on the
     format.
     """
+    device_aliases = cfg.get("device_aliases", {})
+
+    def alias_to_device(cand):
+        name = device_aliases.get(cand)
+        return cloud.device_name_to_device(name or cand) or name
+
     disk_setup = cfg.get("disk_setup")
     if isinstance(disk_setup, dict):
-        update_disk_setup_devices(disk_setup, cloud.device_name_to_device)
+        update_disk_setup_devices(disk_setup, alias_to_device)
         log.debug("Partitioning disks: %s", str(disk_setup))
         for disk, definition in disk_setup.items():
             if not isinstance(definition, dict):
@@ -145,7 +151,7 @@ def handle(_name, cfg, cloud, log, _args):
     fs_setup = cfg.get("fs_setup")
     if isinstance(fs_setup, list):
         log.debug("setting up filesystems: %s", str(fs_setup))
-        update_fs_setup_devices(fs_setup, cloud.device_name_to_device)
+        update_fs_setup_devices(fs_setup, alias_to_device)
         for definition in fs_setup:
             if not isinstance(definition, dict):
                 log.warning("Invalid file system definition: %s" % definition)
@@ -174,7 +180,8 @@ def update_disk_setup_devices(disk_setup, tformer):
             del disk_setup[transformed]
 
         disk_setup[transformed] = disk_setup[origname]
-        disk_setup[transformed]['_origname'] = origname
+        if isinstance(disk_setup[transformed], dict):
+            disk_setup[transformed]['_origname'] = origname
         del disk_setup[origname]
         LOG.debug("updated disk_setup device entry '%s' to '%s'",
                   origname, transformed)
diff --git a/cloudinit/config/cc_mounts.py b/cloudinit/config/cc_mounts.py
index c22d1698..eeb008d2 100644
--- a/cloudinit/config/cc_mounts.py
+++ b/cloudinit/config/cc_mounts.py
@@ -123,7 +123,7 @@ def _is_block_device(device_path, partition_path=None):
     return os.path.exists(sys_path)
 
 
-def sanitize_devname(startname, transformer, log):
+def sanitize_devname(startname, transformer, log, aliases=None):
     log.debug("Attempting to determine the real name of %s", startname)
 
     # workaround, allow user to specify 'ephemeral'
@@ -137,9 +137,14 @@ def sanitize_devname(startname, transformer, log):
         return startname
 
     device_path, partition_number = util.expand_dotted_devname(devname)
+    orig = device_path
+
+    if aliases:
+        device_path = aliases.get(device_path, device_path)
+        if orig != device_path:
+            log.debug("Mapped device alias %s to %s", orig, device_path)
 
     if is_meta_device_name(device_path):
-        orig = device_path
         device_path = transformer(device_path)
         if not device_path:
             return None
@@ -394,6 +399,8 @@ def handle(_name, cfg, cloud, log, _args):
             fstab_devs[toks[0]] = line
             fstab_lines.append(line)
 
+    device_aliases = cfg.get("device_aliases", {})
+
     for i in range(len(cfgmnt)):
         # skip something that wasn't a list
         if not isinstance(cfgmnt[i], list):
@@ -402,7 +409,8 @@ def handle(_name, cfg, cloud, log, _args):
             continue
 
         start = str(cfgmnt[i][0])
-        sanitized = sanitize_devname(start, cloud.device_name_to_device, log)
+        sanitized = sanitize_devname(start, cloud.device_name_to_device, log,
+                                     aliases=device_aliases)
         if sanitized != start:
             log.debug("changed %s => %s" % (start, sanitized))
 
@@ -444,7 +452,8 @@ def handle(_name, cfg, cloud, log, _args):
     # entry has the same device name
     for defmnt in defmnts:
         start = defmnt[0]
-        sanitized = sanitize_devname(start, cloud.device_name_to_device, log)
+        sanitized = sanitize_devname(start, cloud.device_name_to_device, log,
+                                     aliases=device_aliases)
         if sanitized != start:
             log.debug("changed default device %s => %s" % (start, sanitized))