When you create a new EC2 instance, there is a chance you want to run a series of shell scripts to further prepare the instance before it is ready for use. This is possible using a tool called cloud-init.
You have to pass in "user-data" into cloud-init.
As a sidenote, After your instance is built, you can view this data, by going to the following url from inside your instance:
You can use the same method, to view your instance general meta data:
Note: you have to be inside the instance before querying the above url.
$ curl http://169.254.169.254/latest/ # notice the last trailing slash, which makes curl act a bit like the ls command. dynamic meta-data user-data
These 2 urls are useful, if you want to run a ruby/python/bash script from inside your instance and want to use some of this data.
for example here is a sample output if you use curl while logged inside of your instance:
$ curl http://169.254.169.254/latest/meta-data ami-id ami-launch-index hostname . . instance-id public-ipv4 . . ...etc
This show list of "keys" part of key-value pairs. To get the value, for a key, e.g. for public-ipv4, you do:
$ curl http://169.254.169.254/latest/meta-data/public-ipv4 126.96.36.199
The user-data on the other hand displays your custom script that you might have added, e.g.:
$ curl http://169.254.169.254/latest/user-data #!/bin/bash echo "hello world" export env_variable1=value yum install httpd -y
Note, I think the user-data is only available during the instance creation time. If you reboot the vm afterwards, this info gets lost...I think.
Cloud-init has a setting that disables people from logging in as root, this setting is specified in:
This has an ini setting that is:
This actually overrides what sshd's "permitrootlogin" setting is set to. However this cloud setting is only effective once a vm is created and running for the first time. As soon as you reboot, this setting is no longer enforced.