HTC Eris/How-To/Verify A2SD is working
If you are running a ROM which has A2SD baked in to it, or if you added it manually, you can verify if it's working correctly by using the adb tool from the Android SDK.
1. Open a command prompt (cmd.exe in Windows).
2. Change directory to your tools folder under your Android SDK
3. Execute: adb shell
4. This show now show a # at the command prompt. You are now in a shell environment connected to your Android device.
5. Execute: ls -la /data
6. You should now see a directory listing which looks similar to this output
app --> /system/sd/app
app-private --> /system/sd/app-private