[Galaxy S II General] ZACQ8:
Hi mates,

When we are flashing a Custom Rom from the CWM, we are normally instructed by the Devs only to do few steps on CWM like “Wipe Data/Factory Data Reset, Wipe Cache etc.. which we simply follow, but most of the people don’t know, including me, what these options and many other options of CWM are really standing for.

When I googled, I could not find a thread which explains about these options in a single thread, so I would like to share with my friends about what I found the Common Options of the CWM here...

Obviously these are commonly applicable for all the devices which are having CWM, but I am always concern about my favorite Galaxy S II. :D

People who are completely new to Recovery and these options, I suggest them to read this thread first and give a thanks to it's author.

What Is Recovery & Download Mode?

The oder and segregation of the below items in the CWM menu may vary or some of them may be removed in different custom recoveries designed by respective Developer.

CLOCKWORKMODE BASED RECOVERY MENU

1) Reboot Menu :

reboot system now

This one is self-explanatory.

2) Install Menu :

choose zip from (internal/ external) sdcard /

Lets you install any zip file (with any name) from any location on your SD card. The file can be for a ROM, a kernel, an application, a theme or any mod as long as it is in recovery-flashable zip format.

apply /sdcard/update.zip

This one is essentially the same as the ‘apply update from sdcard’ option of the main menu. widely used option for installing a ROM that you have downloaded and copied to your SD card. Entering this option will bring up a screen that will allow you to browse your SD card for the zip file.

apply update from sdcard

This can be used for installation of any official or unofficial update, ROM, kernel, theme etc. that is in a zip format installable from recovery, as long as the file is named update.zip and it has been placed on the root of your SD card (i.e. not in any sub-folder). Selecting this option will bring up a rather annoying confirmation prompt but this has saved us on multiple occasions from a lot of trouble we would have been into due to accidental key presses.

toggle signature verification

Turns the signature verification on and off. When signature verification is on, you will not be able to install any custom ROMs that haven’t been signed by the developers (most custom ROMs aren’t signed). Switching it off skips the signature verification check and proceeds with the installation.

toggle script asserts

Seldom-used option for a vast majority of users. It simply turns script asserts on or off. If you don’t know about these (I don’t), it’s best not to change this option.

3) Wipe Menu

wipe data/factory reset

This option wipes all user data on the device as well as cache. Doing this will leave your phone in the state it was in when you bought it or when any custom ROM was first installed. It will also wipe any sd-ext partition that you might have setup. (see more about sd-ext below under partition)

wipe cache partition

This is a good practice to do this before flashing any ROM. The /cache partition just stores temporary files that are not critical to device operation and can be re-generated easily, this Wipes the cache partition of the device to clear all the data accumulated there over use. This is often used before installing a new ROM, app, kernel or any similar mod via recovery.

Wipe Dalvik Cache

Allows you to wipe the cache for the Dalvik virtual machine. The dalvik cache wipe is quite similar to cache wipe but it stores the post ran java applications. Since Android is JAVA based, it uses the same java virtual machine for compiling. The dalvik cache just stores post-compiled applications in order to speed up the system. Wiping this just forces the system to re-cache those application. It causes no problems but a slight hint of lag on first boot. This is required before most ROM installations and at other occasions too, for fixing some problems.

Wipe Battery Stats

Wipes the saved battery usage statistics and effectively recalibrates the battery. Useful in various scenarios when Android isn’t showing correct battery levels.

4) Nandroid menu

backup and restore Undoubtedly one of the most important features provided by a custom recovery, the backup and restore feature – also known as Nandroid backup – allows you to take a snapshot of your phone’s entire internal memory including all partitions, and save it on the SD card.

Backup

Takes a Nandroid backup, as explained above.

Restore

Lets you restore a previously taken backup. Entering this option presents you with a list of existing backups from the SD card that you can choose from for restoration.

Advanced Restore (new options are available separately to restore from external or internal SDcard in the latest CWM)

This option is similar to the Restore option but once a backup has been selected to be restored, this option allows you to choose what parts of it to restore. You can choose to restore the boot, system, data, cache and sd-ext partitions.

5) Storage menu

mounts and storage

Allows you to perform maintenance tasks on all the internal and external partitions of your android device

mount/unmount /system, /data, /cache, /sdcard, /emmc.

These options let you toggle between mounting or unmounting these respective partitions. Most users don’t need to change these options.

format system, data, cache, sdcard or sd-ext

These let you directly format any of these partitions. Take extreme care with this option as formatting any of these partitions will result in losing all data on them, especially the boot and system partitions. Formatting the system partition will remove your ROM and leave your phone without an operating system while wiping the boot partition may brick your phone unless you restore or flash another one before rebooting your device. See below more explanation about these partitions.

mount USB storage

Lets you enable USB mass storage mode for your SD card right from recovery so that you can connect it to your computer via USB and transfer any files to/from it without having to leave recovery.

6) Advanced

This section contains a few options most users will not require, Here are the options from this section:

Report Error

In case of errors, this feature can be used to save a log of recent ClockworkMod recovery operations on the SD card that you can later report from Android using ROM Manager.

Key Test

Lets you press any of the hardware keys to see if they are properly functioning, and to see their key codes.

Partition SD Card

This option gives you a no-frills way to partition your SD card properly for use with ROMs that support data2ext (a very handy hack for low internal memory devices that enables an /sd-ext partition on the SD card to be used as the internal user data storage i.e. as the /data partition). Once this option is selected, you will be given options to choose the sizes for the /sd-ext partition as well as an optional /swap partition on the SD card, and will then automatically format it for you, leaving the remaining space for normal SD card usage. This option will wipe all data from your SD card so use it with caution!

Fix Permissions

Fixes the file permissions for the internal memory partitions back to default. This is very useful as a fix for several errors and Force-Closes that start appearing after you or an application you installed and provided root access end up messing up the permissions of important files.

PARTITIONS :

The Android uses several partitions to organize files and folders on the device. Each of these partitions has a distinct role in the functionality of the device, but not many Android users know the significance of each partition and its contents. In this guide, we will take you on a tour of Android partitions, what they contain and what can be the possible consequences of modifying their content.

Let’s start with a list of standard internal memory partitions on Android phones and tablets. These are:

•	/boot

•	/system

•	/recovery

•	/data

•	/cache

•	/misc

In addition, there are the SD card partitions.

•	/sdcard

•	/sd-ext

Note that only /sdcard is found in all Android devices and the rest are present only in select devices. Let’s now take a look at the purpose and contents of each of these partitions.

/boot

This is the partition that enables the phone to boot, as the name suggests. It includes the bootloader and the kernel. Without this partition, the device will simply not be able to boot. Wiping this partition from recovery should only be done if absolutely required and once done, the device must NOT be rebooted before installing a new one, which can be done by installing a ROM that includes a /boot partition.

/system

This partition basically contains the entire operating system, other than the kernel and the bootloader. This includes the Android user interface as well as all the system applications that come pre-installed on the device. Wiping this partition will remove Android from the device without rendering it unbootable, and you will still be able to put the phone into recovery or bootloader mode to install a new ROM.

/recovery

The recovery partition can be considered as an alternative boot partition that lets you boot the device into a recovery console for performing advanced recovery and maintenance operations on it. We have already learnt about this partition and its contents above.

/data

Also called userdata, the data partition contains the user’s data – this is where your contacts, messages, settings and apps that you have installed go. Wiping this partition essentially performs a factory reset on your device, restoring it to the way it was when you first booted it, or the way it was after the last official or custom ROM installation. When you perform a wipe data/factory reset from recovery, it is this partition that you are wiping.

/cache

This is the partition where Android stores frequently accessed data and app components. Wiping the cache doesn’t effect your personal data but simply gets rid of the existing data there, which gets automatically rebuilt as you continue using the device.

/misc

This partition contains miscellaneous system settings in form of on/off switches. These settings may include CID (Carrier or Region ID), USB configuration and certain hardware settings etc. This is an important partition and if it is corrupt or missing, several of the device’s features will will not function normally.

/sdcard

This is not a partition on the internal memory of the device but rather the SD card. In terms of usage, this is your storage space to use as you see fit, to store your media, documents, ROMs etc. on it. Wiping it is perfectly safe as long as you backup all the data you require from it, to your computer first. Though several user-installed apps save their data and settings on the SD card and wiping this partition will make you lose all that data.

On devices with both an internal and an external SD card – devices like the Samsung Galaxy SII – the /sdcard partition is always used to refer to the internal SD card. For the external SD card – if present – an alternative partition is used, which differs from device to device. In case of Samsung Galaxy S series devices, it is /sdcard/External_sd while in many other devices, it is /sdcard2. Unlike /sdcard, no system or app data whatsoever is stored automatically on this external SD card and everything present on it has been added there by the user. You can safely wipe it after backing up any data from it that you need to save.

/sd-ext

This is not a standard Android partition, but has become popular in the custom ROM scene. It is basically an additional partition on your SD card that acts as the /data partition when used with certain ROMs that have special features called APP2SD+ or data2ext enabled. It is especially useful on devices with little internal memory allotted to the /data partition. Thus, users who want to install more programs than the internal memory allows can make this partition and use it with a custom ROM that supports this feature, to get additional storage for installing their apps. Wiping this partition is essentially the same as wiping the /data partition – you lose your contacts, SMS, market apps and settings.

Now whenever we install a ROM or mod that requires we to wipe certain partitions before the installation, we should be in a better position to know what we are losing and what not and thus, we’ll know what to backup and what not.

Best Regards