I try to edit android emulator's host file.I follow steps:

```
step1
adb root
step2
adb remount
step3
adb pull /system/etc/hosts .

```

then I add new line for customer host information,then I push hosts file,I get some errors: 

```
   step4
   adb push hosts /system/etc/hosts

```

error information: 

```
adb: error: failed to copy 'hosts' to '/system/etc/hosts': couldn't create file: Read-only file system

```

envirements information: 

```
   osx ei capitan  
   android emulator: android 7.1.1  
   android studio: 2.2.2  

```