Upgrade Firmware

• Trebuchet: This is the default launcher that ships with cyanogenmod. But if you flash gapps then you might loose this.It doesn't have too many features like nova or other launchers but its simple and fast.
• Status bar Tweaks:Status bar has lot of tweaks which include a brightness slider.Slide in status bar to adjust brightness of the screen.Double tap on status bar to sleep device and also network speed indicator for on going traffic info.
• Performance control:A default CPU manager app to control frequencies and governors . You can adjust cpu frequencies and also set them on boot too.
• Theme engine: Theme engine is from the cyanogenmod custom rom which basically changes the look user interface from lock screen  to ring tones all the way up to boot animations.The speciality of the theme engine is the ability to choose individual elements of every theme you have installed.So you like the ring tons and wallpapers of one theme and icons of other theme then you can have them at a time.Just open the theme chooser and you will understand how to do it.
  
• Software Updates: Cyanogenmod is usually available in three types one is nightlies which gets updated with new features every night and are quite stable for daily usage.second one is the snapchat which is monthly build version which will be stable version and other one is the release candidate.Some times nightlies are considered must stable than the snapshots. As of now we have android lollipop 5.1.1  in form on CM 12.1. 
• If you are missing root functionality or all your root apps are not working properly then to developer settings and check if root permissions are set properly.

• Install Htc one v drivers that is sync on your computer if you don't have any recovery installed as we are going to start from scratch.
• You must have updated it to latest official software version that is ice cream sandwich
• Root:You must have root access on your Htc one v.If not then also don't worry as we are going o start from scratch.
• Battery: Charge your One v to at least 90% so that you wont encounter any battery related problems while flashing this rom.
• Backup Efs partitions: This is for those who already have recovery installed.Backup all your efs partition of your htc one v on current Rom or firmware.Just in case if you loose signal you can just restore it back.
• Backup:Backup all your data which includes contacts,apps,photos videos etc everything to computer or any cloud networks as flashing cyanogenmod 12.1 rom on htc one v wipes all your data.
• Custom recovery: You need a custom recovery  installed on your device.Without it you can not flash roms at all.
• You must have a unlocked bootloader.
• Downloads: cm 12.1 for htc one v primou and google apps and transfer them to internal storage.

• Install Htc sinc on your laptop or pc.
• Now power off the device completely and wait for few seconds to confirm that it is completely off.
• Hold volume down and power button at same time for few seconds.When you see hboot release buttons.Using volume keys for navigation select "fastboot" and click on power button to reboot into fastboot.
• Once you are in fastboot mode connect it to computer using usb cable and if you notice any driver installation process let it complete first.
• Download  fastboot on our laptop or Pc and install it.You can install it any where but choose location as c: that is default location.
• open the fastboot folder which you can find it in "c:\programming files".Right click on empty space by holding shift and you see an option "open cmd here".
• If you don't find this option then press windows and R buttons at same time and type cmd to open command prompt.
• Now go to fastboot folder and copy the location of it.
• In command prompt type the command "Cd location of fastboot folder" and press enter.You will notice that fastboot appears in command line.
• Once you are in fastboot window type "fastboot devices" and press enter.If your device is detected you will get a serial number in list of  devices attached.If not uninstall drivers and install them again.
• Now type the command "fastboot oem get_identifier_token" and hit enter.You will get a serial key.Copy that key.
• Now open htcdev.com and register with your email id.
• One you sign up there.Log in to your account and you will find several options if you explore.
• Click on unlock bootloader option and select your other supported devices.
• Proceed all other steps as mentioned and you are are asked to submit Submit your key there.
• You will receive a mail from Htc which includes a unlock_code.bin file. Download it and move it to fastboot folder which is located in programming files.
• Now type the command "fastboot flash unlocktoken unlock_code.bin" and hit enter.Check your device ,you will notice a notification on One v primou to confirm unlocking bootloader. Click on yes.This will unlock bootloder and also erases all data of your Htc one v primou.
• You have a unlocked bootloader device which is ready to accept a recovery to be installed.

#2: Install Twrp recovery on Htc one v 

• Now download twrp recovery for primou from above link and paste it in fastboot folder.Rename img file which you have copied to fastboot folder as recovery so that it will be easy to type command.
• Put the device in fastboot mode again.
• Type the command "fastboot flash recovery recovery.img".This will install latest twrp recovery on your htc one V primou.
• Once you have installed recovery reboot it and copy cyanogenmod 12.1 which you have downloaded on your computer to one V internal storage and head over to next step.

#3: Flash Cyanogenmod 1.2. rom using Twrp

• Download Cm 12.1for  htc one v and Gapps transfer it to sdcard or internal storage of your device.
• Power of  device completely and wait for few seconds to confirm that it is off completely.
• Hold volume down and power button at same time for few seconds.
• When you see hboot release buttons.Using volume keys for navigation select recovery and click on power button to reboot into twrp recovery.
• Once you are in  twrp click on  backup and select all partitions which you want to backup. It might take about 5 minutes for backup to complete. Don't interrupt backup process.
• Once backup of your existing rom is completed click on back button.Wipe data,cache and dalvik cache and wipe system partition too.
• Now select Install and navigate to location where you have placed your cyanogenmod Rom and gapps zip files.
• Flashing this might take about 5 minutes or even less.Once flashing is complete do a factory reset again.
• Now reboot to system.

#4:Flash boot img through fastboot