What is ClockWorkMod (CWM) and how does it work

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ClockworkMod – also known as Clockwork and CWM – is a custom recovery for Android smartphones and tablets that allows you to perform several advanced recovery, restoration, installation and maintenance operations on your Android device that you can't make with your stock recovery. Here we will understand what can we do with CWM and how to do it.


Let's start from the beginning.

What is a recovery?

All Android devices ship with a recovery console that is basically a partition on the device’s internal memory and can be booted into. The stock recovery of almost every Android devices provides a few basic yet handy options that allow you to factory reset your device and also to recover its operating system using an official ROM in zip format, but you can't do nothing more. That’s where a custom recovery comes handy.

A custom Android recovery basically replaces the stock recovery with more options to give you a lot more control on your Android device. With a custom recovery, you can install official and also unofficial ROMs as well as other updates including apps, themes, kernels etc. using .zip files, wipe not just user data but pretty much every partition on your device, mount the storage card for USB mass storage access without leaving recovery, partition your SD card, wipe Dalvik cache and battery stats, fix permissions, perform, manage and restore backups and a lot more...

Introduction to ClockWorkMod (CWM)

ClockWorkMod recovery is one of the most used custom Android recoveries that is available for most mainstream Android devices. This custom recovery is needed to install AOKP, AOSP, CM7 and 9.

Booting into ClockworkMod

On most Android devices, you can enter recovery by powering your device off and then powering it back on while keeping either the ‘Volume Down’ or the ‘Volume-Up’ button pressed, depending on the device. This will enter the bootloader from where you can select the ‘RECOVERY’ option by navigating to it with the Volume key and entering it with the ‘Power’ key.
On most Samsung devices specifically Samsung Galaxy S series devices, you must keep both the ‘Volume-Up’ and ‘Home’ keys pressed while powering on the device, to directly enter recovery.

Features of CWM:

1. Reboot System Now
This one is self-explanatory. You will reboot your system.

2. Apply Update from sdcard
This can be used for installation of any official or unofficial update, ROM, kernel, theme etc. that is in a zipped 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 (and most of the options featured below) 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.

3. Wipe Data/Factory Reset
This option wipes all user data on the device as well as cache. Doing this will leave your Android device 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.

4. Wipe Cache Partition
Wipes the cache partition of the device to clear all the data accumulated there over use. This is often used before installing a different ROM, app, kernel or any similar mod via recovery.

5. Install zip from sdcard]
This option brings up the following sub-menu:
1. apply /sdcard/update.zip
This one is the exactly same as the ‘apply update from sdcard’ option of the main menu.
2. choose zip from sdcard
Lets you install any zip file (with any name) from any location on your SD card. The file can be a ROM, a kernel, an app, a theme or any mod as long as it is in recovery-flashable zip format. This is the most widely used option for installing a ROM that you have downloaded and copied to your SD card.
3. toggle signature verification
Toggles the signature verification. 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.
4. toggle script asserts
Seldom-used option for a vast majority of users. It simply toggles script asserts. If you don’t know about these, it’s best not to change this option.
5. +++++Go Back+++++
Takes you back to the main recovery menu.

6. 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.
1. Backup
Takes a Nandroid backup, as explained above.
2. Restore
Lets you restore a previously taken backup. Entering this option presents you with a list of existing backups from your SD card that you can choose from for restoration.
3. Advanced Restore
This option is similar to the above 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.

7. Mounts and Storage
Allows you to perform maintenance tasks on both internal and external partitions of your android smartphone or tablet
1. mount/unmount /system, /data, /cache, /sdcard or /sd-ext
These options let you toggle between mounting or unmounting these respective partitions. Most users don’t need to change these options.
2. format boot, system, data, cache, sdcard or sd-ext
These let you directly format the choosen partition. 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 fully 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.
3. mount USB storage
Lets you enable USB mass storage mode for your SD card right from the CWM recovery so that you can connect it to your computer via USB and transfer any files to/from it without having to leave recovery.

8. Advanced
"Advances" contains a few options most users will not require, though these can come handy quite often, especially wiping Dalvik cache, which is required before most ROM installations.
1. Reboot Recovery
Lets you directly and very conveniently reboot from recovery right back into recovery. This is useful option for certain back-to-back installations that require the device to at least boot once between them.
2. Wipe Dalvik Cache
Allows you to wipe the cache for the Dalvik virtual machine (the custom-built Java virtual machine for Android).This is required before most ROM installations and at other occasions too, for fixing some problems.
3. Wipe Battery Stats
Wipes the saved battery usage stats and effectively recalibrates the battery. Useful in various scenarios when Android isn’t showing the right battery level.
4. 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.
5. Key Test
Lets you press any of the hardware keys to see if they are properly functioning, and to see their key codes.
6. Partition SD Card
This option gives you a 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 get 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 will wipe all data from your SD card so use it with caution!
7. 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.
 

STEELSKY

Savage Lv6️⃣
Member for 6 years
I hope this was a copy and paste post and all that info isn't jammed into your brain! Thank you though. Makes 100% more sense after reading.
 

silverfox05

In Love Lv4️⃣
Member for 6 years
Thank you for imparting us with your knowledge in such an easy way to understand. :D
 

FaUxTn

Addicted Lv3️⃣
Member for 5 years
this is Classic,'-)
 
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