Implement LIMA_HOME to override ~/.lima location

The `limactl start` command now verifies that the combination
of LimaDir, instance name, and longest socket name is less than
104 characters, and refuses to create the instance otherwise.

Signed-off-by: Jan Dubois <[email protected]>

Author: jandubois

cmd/limactl/start.go

@@ -82,6 +82,12 @@ func loadOrCreateInstance(clicontext *cli.Context) (*store.Instance, error) {
 		return nil, err
 	}
 
+	// all socket names should be 6 characters or less
+	maxSockName := filepath.Join(instDir, "serial.sock")
+	if len(maxSockName) >= 104 {
+		return nil, errors.Errorf("Instance name %q too long: %q must be less than 104 characers, but is %d",
+			instName, maxSockName, len(maxSockName))
+	}
 	if _, err := os.Stat(instDir); !errors.Is(err, os.ErrNotExist) {
 		return nil, errors.Errorf("instance %q already exists (%q)", instName, instDir)
 	}

pkg/store/store.go

@@ -12,17 +12,20 @@ import (
 // DotLima is a directory that appears under the home directory.
 const DotLima = ".lima"
 
-// LimaDir returns the abstract path of `~/.lima`.
+// LimaDir returns the abstract path of `~/.lima` (or $LIMA_HOME, if set).
 //
 // NOTE: We do not use `~/Library/Application Support/Lima` on macOS.
 // We use `~/.lima` so that we can have enough space for the length of the socket path,
 // which can be only 104 characters on macOS.
 func LimaDir() (string, error) {
-	homeDir, err := os.UserHomeDir()
-	if err != nil {
-		return "", err
+	dir := os.Getenv("LIMA_HOME")
+	if dir == "" {
+		homeDir, err := os.UserHomeDir()
+		if err != nil {
+			return "", err
+		}
+		dir = filepath.Join(homeDir, DotLima)
 	}
-	dir := filepath.Join(homeDir, DotLima)
 	return dir, nil
 }