CyanogenMod on Samsung Galaxy S III

I've been considering installing a custom ROM on my Samsung Galaxy S III for a while now. There are some advantages to leaving it as standard, for me the main reason was that I could sync the calendar and contacts with Outlook at work using Kies. That stopped working this week, and combined with the latest update, which made my phone even more laggy and greatly reduced my battery time, it made me decide to finally take the leap.

There is a huge number of custom ROMs available, the choice fell on CyanogenMod simply because it is one of the more well known and most used. I use this phone for work as well as home, so I wanted something at least fairly stable. This is also why I chose to go for version 10.2, which uses Android 4.3 Jelly Bean, rather than version 11 which uses Android 4.4 KitKat (which is still releasing nightly builds).

I've only used it for a day so far, but I'm quite happy with it. The 2 things that I wanted most to improve by installing CyanogenMod, battery life and speed, have surpassed my expectations. Battery life is hugely better, and there is no lag at all.Maybe I'll write up a more thorough review after using it for a while.

What is shown on the boot-screen after install

So, here is how to install it. But before we begin, a couple of things to consider.

• The standard renunciation of responsibility: I take no responsibility for anything that might happen as a result of your using this guide. By installing a custom ROM (like CyanogenMod) you will almost certainly be voiding your warranty. Also, there is a chance of bricking your phone when doing this (The phone will not work at all if this happens). I personally don't think the chances of bricking your phone are very large, as long as you follow the steps, but I take no responsibility if you do.
• Make sure that the battery is fully charged before starting the procedure.
• Copy any files that you want to be sure to keep from your phone to your computer before starting the procedure.
• Any game progress, notes, etc will be lost, even if you reinstall the app afterwards.
• I'm using Linux Mint 16 for the few steps that require a computer, if you are using Windows or Mac OS X, additional steps may be required to get the tools to work. 
• CyanogenMod doesn't include Google apps by default, and yes, this includes the Play Store. Since you will probably want it (and because I do), I have included it in the steps below. If, for whatever reason, you do not want it, just ignore those steps.
• I exported my contact to a vcf file before installing. As it turns out, the contacts app in CyanogenMod doesn't support this format for importing, so you might need to convert the file to vCard.
• I used this entry from the CyanogenMod wiki as my main guide, it's a good idea to check in there, to see if there are updated versions of programs etc.

1. Download the programs/files that you will need
1. Heimdall, Used to transfer the recovery image to the phone. Choose the version corresponding to your OS. Even if Heimdall exists in your repositories, it is recommended to get it directly so that you are sure that it is the latest version.
2. Koush's ClockworkMod Recovery, recovery image that allows you to flash the custom ROM.
3. CyanogenMod, your new ROM. Choose the image you want, I went with  cm-10.2.0-i9300.zip, which is marked as "stable".
4. Google apps, if you want Play Store, GMail etc.
2. Install Heimdall on your PC.
3. Connect your phone to your PC, and place the zip-files for CyanogenMod and Google apps on your SD-card.
4. Switch off your phone, do not have it connected to the computer.
5. On your phone, hold down the Volume down, Home, and Power buttons. It will start up in flash-mode. Accept the disclaimer, then connect the phone to your computer by USB.
6. On your computer, rename your ClockworkMod recovery zip-file to "recovery.zip", open a Terminal and go to the directory where you have your ClockworkMod recovery zip-file. Give the following command: 
1. sudo heimdall flash --RECOVERY recovery.img --no-reboot 
7. Once the command has terminated and you're back to a command line on your computer, and your phone has a full blue progress indicator, unplug the USB, and pull the battery out from your phone.
1. The reason for pulling the battery is that if the phone reboots at this point, the stock ROM can overwrite your new custom recovery.
8. Put the battery back, and , hold down the Volume up, Home, and Power buttons. It will now start up in recovery-mode.It should clearly state that it is ClockworkMod Recovery, if it doesn't then the recovery image has probably been overwritten by the stock ROM, start again from step 4.
9. Use the Volume up/down to navigate, and power button to select from the menu. You will probably want to select "Backup and restore", and perform a backup of your current ROM. This will allow you to go back to your stock ROM should you ever want to.
10. Select "Wipe data/factory reset".
11. Select "Install zip". The next selection depends on where you placed your file, internal or external sdcard. I used an external one (the one you insert next to the battery), so I chose "choose zip from /storage/sdcard1". Select the CyanogenMod zip-file and wait for it to finish installing.
12. Go back the main menu and select "reboot system now".
13. For installing Google apps, repeat steps 8 and 11.
14. Start downloading apps and configuring you new phone!

Flash-mode, confirm to continue

Flash-mode, ready for new recovery image

ClockworkMod recovery mode