Question

I’m able to install own application into /system/app using adb shell commands. But how to uninstall it? Is there any commands to do it? My phone is rooted.

Answer 1

Manual uninstall using ADB :
http://www.careace.net/2010/05/12/how-to-remove-android-apps-through-adb/

During website downtime (like now) see crawled snapshot here:
https://web.archive.org/web/20180222063358/http://www.careace.net/2010/05/12/how-to-remove-android-apps-through-adb/

Programmatically:

    public static void deleteFromSystem (final String file)
    {
        try 
        {
            if (new File(file).exists())
            {
                String  path        = new File(file).getParent();
                Process process     = Runtime.getRuntime().exec("su");
                DataOutputStream os = new DataOutputStream(process.getOutputStream());
                os.writeBytes("mount -o rw,remount /system; \n");
                os.writeBytes("chmod 777 "      + path + "; \n");
                os.writeBytes("chmod 777 "      + file + "; \n");
                os.writeBytes("rm -r "          + file + "; \n");
                os.writeBytes("mount -o ro,remount /system; \n");
                os.writeBytes("reboot \n");
                os.flush();
                os.close();
                process.waitFor();
            }
        } 
        catch (Throwable e) {e.printStackTrace();}
    }