数据库是保存用户数据的文件，包括默认的设置和个人重新设置的数据，这些数据保存在/data/data下的各个以
apk包名为目录名的路径下：
#cd /data/data
#busybox find ./ -name "*.db" -print
./com.Android.email/databases/EmailProviderBody.db
./com.android.email/databases/EmailProvider.db
./com.android.rk.books/databases/books.db
./com.android.providers.contacts/databases/contacts2.db
./com.google.android.gm/databases/gmail.db
./com.google.android.gm/databases/downloads.db
./com.android.vending/databases/assets.db
./com.android.providers.media/databases/internal.db
./com.android.providers.media/databases/external.db
./com.android.deskclock/databases/alarms.db
./yd.spreadwin.launcher/databases/launcher.db
./com.android.providers.calendar/databases/calendar.db
./com.darshancomputing.BatteryIndicatorPro/databases/alarms.db
./com.darshancomputing.BatteryIndicatorPro/databases/logs.db
./com.google.android.gsf/databases/googlesettings.db
./com.google.android.gsf/databases/subscribedfeeds.db
./com.google.android.gsf/databases/talk.db
./com.google.android.gsf/databases/gservices.db
./com.google.android.gsf/databases/gls.db
./com.cooliris.media/databases/picasa.db
./com.android.providers.downloads/databases/downloads.db
./com.android.providers.settings/databases/settings.db
手动删除掉这些数据库文件，重启机器后相关的应用就会使用默认值重新加载数据库，如设置应用的数据库：
/data/data/com.android.providers.settings/databases/settings.db
删掉settings.db，重启即可删掉设置里的个人设置的数据。