Adds support for 'defer' when writing files.

FsCloudInit/Builders.fs

@@ -46,6 +46,9 @@ module Builders =
         [<CustomOperation "append">]
         member _.Append (writeFile:WriteFile, append:bool) =
             { writeFile with Append = append }
+        [<CustomOperation "defer">]
+        member _.Defer (writeFile:WriteFile, defer:bool) =
+            { writeFile with Defer = defer }
 
     let writeFile = WriteFileBuilder ()
 

FsCloudInit/CloudConfig.fs

@@ -49,6 +49,7 @@ type WriteFile =
         [<YamlDotNet.Serialization.YamlMember(ScalarStyle = YamlDotNet.Core.ScalarStyle.SingleQuoted)>]
         Permissions : string
         Append : bool
+        Defer : bool
     }
     static member Default =
         {
@@ -58,6 +59,7 @@ type WriteFile =
             Path = null
             Permissions = null
             Append = false
+            Defer = false
         }
 
 type AptSource =

FsCloudInitTests/BuilderTests.fs

@@ -68,6 +68,20 @@ let tests =
             |> Writer.write
             |> matchExpectedAt "file-embedding-readonly.yaml"
         }
+        test "Embed file with defer builder" {
+            cloudConfig {
+                write_files [
+                    writeFile {
+                        path "/var/lib/data/hello"
+                        content "hello world"
+                        owner "azureuser:azureuser"
+                        defer true
+                    }
+                ]
+            }
+            |> Writer.write
+            |> matchExpectedAt "file-embedding-defer.yaml"
+        }
         testAsync "Install dotnet with aptSource builders" {
             let! aptSourceRes = http.GetAsync "https://packages.microsoft.com/config/ubuntu/20.04/prod.list" |> Async.AwaitTask
             let! aptSourceVal = aptSourceRes.Content.ReadAsStringAsync () |> Async.AwaitTask

FsCloudInitTests/TestContent/file-embedding-defer.yaml

@@ -0,0 +1,7 @@
+#cloud-config
+write_files:
+- encoding: b64
+  content: aGVsbG8gd29ybGQ=
+  owner: azureuser:azureuser
+  path: /var/lib/data/hello
+  defer: true

README.md

@@ -161,6 +161,22 @@ cloudConfig {
 |> Writer.write
 ```
 
+If you are writing files that should be owned by users other than `root`, you often need to use `defer` so they are not written until after that user exists. When not deferred, depending on the version of cloud-init, the file may not be written or it may end up owned by `root`.
+
+```f#
+cloudConfig {
+    write_files [
+        writeFile {
+            path "/var/lib/data/hello"
+            content "hello world"
+            owner "myuser:myuser"
+            defer true
+        }
+    ]
+}
+|> Writer.write
+```
+
 #### Install packages
 
 ```f#