tart set: bring back the --disk-size command-line argument (#694)

* tart set: bring back the --disk-size command-line argument * Add a --disk-size explainer
cirruslabs · Jan 3, 2024 · 4c33064 · 4c33064
1 parent 1a267d4
commit 4c33064
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Showing 3 changed files with 25 additions and 3 deletions.
diff --git a/Sources/tart/Commands/Set.swift b/Sources/tart/Commands/Set.swift
@@ -16,7 +16,18 @@ struct Set: AsyncParsableCommand {
   @Option(help: "VM display resolution in a format of <width>x<height>. For example, 1200x800")
   var display: VMDisplayConfig?
 
-  @Option(help: .hidden)
+  @Option(help: ArgumentHelp("Resize the VMs disk to the specified size in GB (note that the disk size can only be increased to avoid losing data",
+                             discussion: """
+                             Disk resizing works on most cloud-ready Linux distributions out-of-the box (e.g. Ubuntu Cloud Images
+                             have the \"cloud-initramfs-growroot\" package installed that runs on boot) and on the rest of the
+                             distributions by running the \"growpart\" or \"resize2fs\" commands.
+
+                             For macOS, however, things are a bit more complicated: you need to remove the recovery partition
+                             first and then run various \"diskutil\" commands, see Tart's packer plugin source code for more
+                             details[1].
+
+                             [1]: https://github.com/cirruslabs/packer-plugin-tart/blob/main/builder/tart/step_disk_resize.go
+                             """))
   var diskSize: UInt16?
 
   func run() async throws {

diff --git a/Sources/tart/VMDirectory.swift b/Sources/tart/VMDirectory.swift
@@ -134,9 +134,17 @@ struct VMDirectory: Prunable {
     if !FileManager.default.fileExists(atPath: diskURL.path) {
       FileManager.default.createFile(atPath: diskURL.path, contents: nil, attributes: nil)
     }
+
     let diskFileHandle = try FileHandle.init(forWritingTo: diskURL)
-    // macOS considers kilo being 1000 and not 1024
-    try diskFileHandle.truncate(atOffset: UInt64(sizeGB) * 1000 * 1000 * 1000)
+    let currentDiskFileLength = try diskFileHandle.seekToEnd()
+    let desiredDiskFileLength = UInt64(sizeGB) * 1000 * 1000 * 1000
+    if desiredDiskFileLength <= currentDiskFileLength {
+      let currentLengthHuman = ByteCountFormatter().string(fromByteCount: Int64(currentDiskFileLength))
+      let desiredLengthHuman = ByteCountFormatter().string(fromByteCount: Int64(desiredDiskFileLength))
+      throw RuntimeError.InvalidDiskSize("new disk size of \(desiredLengthHuman) should be larger " +
+        "than the current disk size of \(currentLengthHuman)")
+    }
+    try diskFileHandle.truncate(atOffset: desiredDiskFileLength)
     try diskFileHandle.close()
   }
 

diff --git a/Sources/tart/VMStorageHelper.swift b/Sources/tart/VMStorageHelper.swift
@@ -55,6 +55,7 @@ enum RuntimeError : Error {
   case VMAlreadyRunning(_ message: String)
   case NoIPAddressFound(_ message: String)
   case DiskAlreadyInUse(_ message: String)
+  case InvalidDiskSize(_ message: String)
   case FailedToUpdateAccessDate(_ message: String)
   case PIDLockFailed(_ message: String)
   case FailedToParseRemoteName(_ message: String)
@@ -92,6 +93,8 @@ extension RuntimeError : CustomStringConvertible {
       return message
     case .DiskAlreadyInUse(let message):
       return message
+    case .InvalidDiskSize(let message):
+      return message
     case .FailedToUpdateAccessDate(let message):
       return message
     case .PIDLockFailed(let message):