I am using raspberry which is running raspbian jessie OS.
I tried to install/upgrade the aws-cli using steps provided at https://aws.amazon.com/cli/
Even after upgrade was successful, I get below output

This was same before installation.
Drawbacks:
I am not able to see ‘iot’ as option when I run aws help. Majority of other services like ec2 & s3 are available

What can be the reason behind this behavior? How to solve this?

Like me, your old version of the AWS CLI would have been installed via PIP (python package installer).

If you do which aws you will see something like so ...Python/2.7/bin/aws

You then tried to upgrade using the official AWS package installer – e.g. https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2-mac.html#cliv2-mac-install-cmd

This method installs the new version in a location like /usr/local/bin/aws

So you basically have 2 versions of the AWS CLI on your system. When you do aws --version you are seeing the old PIP based installation.

To fix it (as I did) – I just used PIP to upgrade existing CLI:

• pip install awscli --upgrade --user (i had to use –user or there was an error)
• now when I ran aws --version – I can see a newer version
• I then cleaned up my other AWS package installer using steps here – https://docs.aws.amazon.com/cli/latest/userguide/install-cliv2-mac.html#cliv2-mac-remove