If you have not used a rooted Galaxy S5 before, you probably want to read the rest of this tutorial on how to backup and restore ROM on your S5.
What is a ROM backup?
A ROM backup consists of everything on your phone, your whole OS along with all of your settings, apps, app data, and everything else except the contents of your personal files such as videos, photos, and others. Backing up a ROM means you are making an exact 100% copy of your current OS. Whether you are running stock ROM or CyanogenMod11, backing up ROM will backup your current ROM. Think of it as System Backup for Windows or TimeMachine for OSX.
The Galaxy S5 by default does not have this feature to backup everything on your phone but with a rooted Galaxy S5, you can make a complete backup of your Galaxy S5. If you happen to lose your phone one day, you can easily restore your phone back (without starting over) if you saved a copy of your backup ROM on your hard disk (or microSD card or even USB Flash if you use USB OTG cable).
Now, backing up ROM is also useful when installing new custom ROMs as you will be able to easily restore to your previous ROM with all of your settings/apps if something goes wrong. For those of you who’ve never backed up your current ROM after rooting your Galaxy S5, we highly suggest to do this at least once and copy your backup ROM somewhere safe on your computer hard disk. (You can even encrypt your ROM backup folder with a password using zip or 7zip.)
How to Make Backup ROM on Rooted Galaxy S5!
Before we begin, you MUST have a rooted Galaxy S5 with either CWM or TWRP recovery installed. We will be using Philz CWM Recovery (which we recommend) in this tutorial and if you are using TWRP Recovery, menus might be slightly different.