Docker Toolbox 1.8.1.c Install failed

I kept getting this failure when install the toolbox on OS X 10.10.5

Sep 3 12:25:04 installd[473]: PackageKit: ----- Begin install -----
Sep 3 12:25:09 installd[473]: PackageKit: Install Failed: Error Domain=PKInstallErrorDomain Code=112 “An error occurred while running scripts from the package “DockerToolbox-1.8.1c.pkg”.” UserInfo=0x7fddfc036f20 {NSFilePath=./postinstall, NSURL=file://localhost/Users/weixiang/Downloads/DockerToolbox-1.8.1c.pkg#boot2dockeriso.pkg, PKInstallPackageIdentifier=io.boot2dockeriso.pkg.boot2dockeriso, NSLocalizedDescription=An error occurred while running scripts from the package “DockerToolbox-1.8.1c.pkg”.} { NSFilePath = “./postinstall”; NSLocalizedDescription = “An error occurred while running scripts from the package \U201cDockerToolbox-1.8.1c.pkg\U201d.”;NSURL = “file://localhost/Users/weixiang/Downloads/DockerToolbox-1.8.1c.pkg#boot2dockeriso.pkg”; PKInstallPackageIdentifier = “io.boot2dockeriso.pkg.boot2dockeriso”;}
Sep 3 12:25:09 Installer[461]: Install failed: The Installer encountered an error that caused the installation to fail. Contact the software manufacturer for assistance.

how exactly are you installing this?

could this be a rights issue?

What do you mean by how I install it?
I just download the pkg file from the web and installed it from there.

In my case, after I opened PKG file, and double clicked the continue button, the installation window just did not show the overview list. Go back button did not work neither. My mac version is 10.8.5… Any comment is welcome. boot2docker was ok to complete its installation by the way.