adb - How to mount /system rewritable or read-only? (RW/RO)

How can I mount the /system directory rewritable or read-only on my Android phone?

Answer

There are a few methods how you can mount your /system directory RW or RO. However, it will require root.

1. 
   
   

   Connect your phone to the computer. (Make sure USB debugging is enabled on your phone)

   
   


2. 
   

   Open CMD/Terminal on your PC.

   
   
   
   
   • 
     

     Windows: CTRL + R, then type cmd.

     
     
   
   
   • 
     

     Ubuntu: CTRL + ALT + T.

     
     
     
   
   
   • 
     

     Mac: Navigate to /Applications/Utilities/ and double-click on Terminal.

     
     
   
   
   
   


3. 
   

   Type this:

   
   
   
   
   1. adb shell
   
   
   
   2. 
      

      su

      
      
   
   
   3. 
      

      Choose one: (for security mount /system back to RO when finished)

      
      
      
      
      • Mount system RW: mount -o rw,remount /system
      
      
      • Mount system RO: mount -o ro,remount /system
      
      
      
      
   
   
   
   
   

1. Open terminal on your android phone (download here):


2. 
   

   Type this in the terminal:

   
   
   
   
   1. 
      
      

      su

      
      
   
   
   2. 
      

      Choose one: (for security mount /system back to RO when finished)

      
      
      
      
      • Mount system RW: mount -o rw,remount /system
      
      
      • Mount system RO: mount -o ro,remount /system
      
      
      
      
   
   
   
   
   

If you don't want to type the command every time in the terminal, I've written an app designed to do this for you:

Android 2.3

For people running Android 2.3 and the command fails, look at this answer: https://android.stackexchange.com/a/125437/95577