error "read only file system" when I'm trying to create file using bash script in AWS Lambda function (python)

Question

I have python (3.8) Lambda function that connected to EFS, in mount /mnt/my-mount.

I want to run a bash script via the function, so I created another file script.sh.

This is the python function:

import json
import os

def lambda_handler(event, context):
    os.system("sh script.sh")

and bash script script.sh:

#!/bin/bash
touch hello.txt

and I get the following error:

cannot touch script.sh: Read-only file system

Notes:

• I can create file using the python function (f.write).
• If I run os.system("chmod 777 a.sh"), again I get Read-Only file system.
• If I use rc = subprocess.call("bash a.sh"), I get No such file or directory: 'bash a.sh'
• The EFS has access point for user 1000:1000 with 777 permissions.

Answer 1

This could be due to having the Lambda role without proper write permissions. You should attach the proper policy or define your custom one: