Upgrade AT&T Galaxy S2 i777 to Android 4.2.1 via Cyanogenmod 10.1 [Jelly Bean]

One month ago, Samsung announced a list of devices that are getting Android 4.1 Jelly Bean. Galaxy S2 is one of them & it was a quiet good news for Galaxy S2 owners. Eventually Samsung released the JB update for the Galaxy S3 but still testing the firmware for Galaxy S2. In future, after rolling out update for Galaxy S2 I9100 (international variant), it will take some time for AT&T to make some carrier specific changes in the official firmware. This whole process will take around one month for them to provide an update for their S2 users. (This can be concluded from the time required for AT&T to release the Android 4.1 update for Galaxy S3 i747 since Samsung released it for international variant).

Now you should forget Android 4.1 as Google has rolled another update to Jelly Bean viz, Android 4.2. A new flavor of Jelly Bean includes lot many improvements & missing features from the Android 4.1. It has got some interesting things like Daydream, expandable & actionable notifications, photo sphere camera, smarter keyboard with gesture typing, a new look for Google Search etc. And beyond these things, it is ultra fast & buttery smooth. We hope AT&T would soon provide Android 4.1 &thenceforth Android 4.2 for their S2 users.

But don’t worry, before AT&T, Cyanogenmod is here to fulfill your wish. Cyanogenmod is a custom ROM that provides you the latest firmware updates straight from the original Android source (i.e, without modifying the original Android). Along with that it includes its own customization settings & tweaks. And now it is available for AT&T Galaxy S2 i777.

Read on further to learn how to update AT&T Galaxy S2 to Android 4.2.1 via Cyanogenmod 10.1 Custom ROM.

Disclaimer: The procedure given in this tutorial is considered as risky and may cause damage to your phone. It is recommended that you should not follow it unless you are familiar with these things. Follow this guide completely at your own risk. Neither we nor Cyanogenmod team will be held responsible for any damage caused to your device while attempting these steps.

The guide is compatible only for AT&T Galaxy S2 SGH-i777 (US Variant). Dont try it on any other device or variant of the same else it may result in permanent damage to your device.


  • Charge your device up to 75% battery level so that ROM installation won’t be interrupted.
  • Enable / Tick ‘USB Debugging’ option in your phone.
  • It is highly recommended to backup all your data from internal memory (includes contacts, messages (SMS/MMS), call logs, Internet APNs etc.). Your phone data will get lost after installation of this ROM (excluding External storage).
  • It is necessary to have Custom Recovery like Clockworkmod / TWRP installed in your phone for flashing Cyanogenmod 10.1 Custom ROM.

Procedure to Upgrade AT&T Galaxy S2 SGH-i777 to Android 4.2.1 Custom ROM (Cyanogenmod 10.1):

  • Download Google Apps (Gmail, Maps, GTalk, Play Store etc.) from the link given below.
  1. Google Apps for Jelly Bean
  • After downloading ROM package & Google Apps, connect your phone to the PC. Enable mass storage mode to access external SD card data & transfer both the files on the root directory of it.
  • Disconnect the phone from computer. Now boot into Clockworkmod recovery. To do so, switch off the phone completely (until it vibrates). Press & hold Volume Up + Volume down Button + Power Key together until recovery mode appears (you can release power button after Samsung logo appears but keep holding other two until recovery mode shows up).
  • After getting into the recovery, make a nandroid backup of your current ROM so that it can be restored back in case of failure. To do so, Highlight backup and restore option in the recovery menu, select it & then choose backup to start the backup process.
  • Select wipe data/factory reset & subsequently wipe cache partition to wipe the data & caches respectively from the internal memory. (Caution! performing this step will erase all the data from internal memory, which includes sms/mms, contacts, reminders, APNs, call logs, apps etc. therefore ensure that youve taken backup of all these things before).
  • Now select install zip from sdcard & then on next screen select, choose zip from sdcard. It will show you the files & folders located on the SD card of your device. Navigate to the ROM file, select it using power button (unless youre using touch CWM) & confirm the installation by pressing on Yes. This should start installing the ROM.
  • Again select install zip from sdcard followed by choose zip from sdcard & this time browse for Google apps package file (gapps-jb-20121212-signed.zip). Press on Yes to install confirm Google Apps installation.
  • After you finish flashing all the files, Select “reboot system now” to Restart the phone.

Tip: You can restore back your previous ROM using CMW’s restore feature. To restore the previous ROM, boot into the recovery mode, selectBackup and Restoreoption & on next screen, selectrestore.Now choose the backup you like to restore (or the restore the backup you’ve made before flashing this ROM).

Congratulations!! You’ve successfully updated your AT&T Galaxy S2 SGH-i777 to Android 4.2.1 with Cyanogenmod 10.1 Custom ROM. Let us know if you’ve any problems, we’ll try our best to sort out them. And lastly don’t forget to check get.cm page (Official Download Page) for latest updates & bug fixes. Enjoy..

Comments (8)
  1. h.e.u Devil October 19, 2013
  2. Putra October 6, 2013
  3. Himesh May 23, 2013
  4. Thi Ken May 14, 2013
    • Viraj SK May 14, 2013
  5. David Huff April 27, 2013
    • Shreyas April 27, 2013

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