# AWS Systems Manager 1. [TL;DR](#tldr) 1. [Requirements](#requirements) 1. [Gotchas](#gotchas) 1. [Integrate with Ansible](#integrate-with-ansible) 1. [Troubleshooting](#troubleshooting) 1. [Check node availability using `ssm-cli`](#check-node-availability-using-ssm-cli) 1. [Further readings](#further-readings) 1. [Sources](#sources) ## TL;DR
Usage ```sh # Get connection statuses. aws ssm get-connection-status --target 'instance-id' # Start sessions. aws ssm start-session --target 'instance-id' # Run commands. aws ssm start-session \ --target 'instance-id' \ --document-name 'CustomCommandSessionDocument' \ --parameters '{"logpath":["/var/log/amazon/ssm/amazon-ssm-agent.log"]}' aws ssm send-command \ --instance-ids 'i-0123456789abcdef0' \ --document-name 'AWS-RunShellScript' \ --parameters "commands="echo 'hallo'" # Wait for commands execution. aws ssm wait command-executed --instance-id 'i-0123456789abcdef0' --command-id 'abcdef01-2345-abcd-6789-abcdef012345' # Get commands results. aws ssm get-command-invocation --instance-id 'i-0123456789abcdef0' --command-id 'abcdef01-2345-abcd-6789-abcdef012345' aws ssm get-command-invocation \ --instance-id 'i-0123456789abcdef0' --command-id 'abcdef01-2345-abcd-6789-abcdef012345' \ --query '{"status": Status, "rc": ResponseCode, "stdout": StandardOutputContent, "stderr": StandardErrorContent}' ```
Real world use cases Also check out the [snippets]. ```sh # Connect to instances if they are available. instance_id='i-08fc83ad07487d72f' \ && eval $(aws ssm get-connection-status --target "$instance_id" --query "Status=='connected'" --output 'text') \ && aws ssm start-session --target "$instance_id" \ || (echo "instance ${instance_id} not available" >&2 && false) # Run commands and get their output. instance_id='i-0915612f182914822' \ && command_id=$(aws ssm send-command --instance-ids "$instance_id" \ --document-name 'AWS-RunShellScript' --parameters 'commands="echo hallo"' \ --query 'Command.CommandId' --output 'text') \ && aws ssm wait command-executed --command-id "$command_id" --instance-id "$instance_id" \ && aws ssm get-command-invocation --command-id "$command_id" --instance-id "$instance_id" \ --query '{"status": Status, "rc": ResponseCode, "stdout": StandardOutputContent, "stderr": StandardErrorContent}' ```
## Requirements For instances to be managed by Systems Manager and be available in lists of managed nodes, it must: - Run a supported operating system. - Have the SSM Agent installed **and running**. ```sh sudo dnf -y install 'amazon-ssm-agent' sudo systemctl enable --now 'amazon-ssm-agent.service' ``` - Have an AWS IAM instance profile attached with the correct permissions.
The instance profile enables the instance to communicate with the Systems Manager service. **Alternatively**, the instance must be registered to Systems Manager using hybrid activation. The minimum permissions required are given by the Amazon-provided `AmazonSSMManagedInstanceCore` policy (`arn:aws:iam::aws:policy/AmazonSSMManagedInstanceCore`). - Be able to to connect to a Systems Manager endpoint through the SSM Agent in order to register with the service.
From there, the instance must be available to the service. This is confirmed by the service by sending a signal every five minutes to check the instance's health. After the status of a managed node has been `Connection Lost` for at least 30 days, the node could be removed from the Fleet Manager console.
To restore it to the list, resolve the issues that caused the lost connection. Check whether SSM Agent successfully registered with the Systems Manager service by executing the `aws ssm describe-instance-associations-status` command.
It won't return results until a successful registration has taken place. ```sh aws ssm describe-instance-associations-status --instance-id 'instance-id' ```
Failed invocation ```json { "InstanceAssociationStatusInfos": [] } ```
Successful invocation ```json { "InstanceAssociationStatusInfos": [ { "AssociationId": "51f0ed7e-c236-4c34-829d-e8f2a7a3bb4a", "Name": "AWS-GatherSoftwareInventory", "DocumentVersion": "1", "AssociationVersion": "2", "InstanceId": "i-0123456789abcdef0", "ExecutionDate": "2024-04-22T14:41:37.313000+02:00", "Status": "Success", "ExecutionSummary": "1 out of 1 plugin processed, 1 success, 0 failed, 0 timedout, 0 skipped. ", "AssociationName": "InspectorInventoryCollection-do-not-delete" }, … ] } ```
## Gotchas - SSM starts shell sessions under `/usr/bin` ([source][how can i change the session manager shell to bash on ec2 linux instances?]): > **Other shell profile configuration options**
> By default, Session Manager starts in the "/usr/bin" directory. - **Avoid** executing SSM through commands like `xargs` or `parallel` like in the following: ```sh aws ec2 describe-instances --output text --query 'Reservations[].Instances[0].InstanceId' --filters … \ | xargs -ot aws ssm start-session --target ``` The middle commands start the session correctly, but will intercept traps like `CTRL-C` and stop their own execution terminating the SSM session. Prefer using the `describe-instance` command's output as input for the `start-session` command instead: ```sh aws ssm start-session --target "$( \ aws ec2 describe-instances --output text --query 'Reservations[].Instances[0].InstanceId' --filters … \ )" ``` ## Integrate with Ansible Create a dynamic inventory which name ends with `aws_ec2.yml` (e.g. `test.aws_ec2.yml` or simply `aws_ec2.yml`).
Refer the [amazon.aws.aws_ec2 inventory] for more information about the file specifications.
It needs to be named like that to be found by the ['community.aws.aws_ssm' connection plugin][community.aws.aws_ssm connection]. ```yml # File: 'aws_ec2.yml'. plugin: aws_ec2 regions: - eu-east-2 exclude_filters: - tag-key: - aws:eks:cluster-name # EKS nodes do not use SSM-capable images include_filters: - instance-state-name: running keyed_groups: - key: tags.Name # add hosts to 'tag_Name_' groups for each aws_ec2 host's 'Tags.Name' attribute prefix: tag_Name_ separator: "" - key: tags.application # add hosts to 'tag_application_' groups for each aws_ec2 host's 'Tags.application' attribute prefix: tag_application_ separator: "" hostnames: - instance-id # acts as keyword to use the instances' 'InstanceId' attribute # use 'private-ip-address' to use the instances' 'PrivateIpAddress' attribute instead # or any option in really ``` Pitfalls: - One **shall not use the `remote_user` connection option**, as it is not supported by the plugin.
From the [plugin notes][aws_ssm connection plugin notes]: > The `community.aws.aws_ssm` connection plugin does not support using the `remote_user` and `ansible_user` variables > to configure the remote user. The `become_user` parameter should be used to configure which user to run commands > as. Remote commands will often default to running as the `ssm-agent` user, however this will also depend on how SSM > has been configured. - SSM sessions' duration is limited by SSM's _idle session timeout_ setting.
That might impact tasks that need to run for more than said duration.
Some modules (e.g.: `community.postgresql.postgresql_db`) got their session terminated and SSM retried the task, killing and restarting the running process.
Since the process lasted more than the sessions' duration, it kept having its sessions terminated. The task failed when the SSM reached the set retries for the connection.
Consider extending the SSM idle session timeout setting, or using `async` tasks (which come with their own SSM caveats) to circumvent this issue. - Since [SSM starts shell sessions under `/usr/bin`][gotchas], one must explicitly set Ansible's temporary directory to a folder the remote user can write to ([source][ansible temp dir change]).
```sh ANSIBLE_REMOTE_TMP="/tmp/.ansible-${USER}/tmp" ansible… ``` ```ini # file: ansible.cfg remote_tmp=/tmp/.ansible-${USER}/tmp ``` ```diff - hosts: all + vars: + ansible_remote_tmp: /tmp/.ansible-ssm-user/tmp tasks: … ```
This, or use the shell profiles in [SSM's preferences][session manager preferences] to change the directory when logged in. - In similar fashion to the point above, SSM might mess up the directory used by `async` tasks.
To avoid this, set it to a folder the remote user can write to.
```sh ANSIBLE_ASYNC_DIR="/tmp/.ansible-${USER}/async" ansible… ``` ```ini # file: ansible.cfg async_dir=/tmp/.ansible-${USER}/async ``` ```diff - hosts: all + vars: + ansible_async_dir: /tmp/.ansible-ssm-user/async tasks: … ```
- When using `async` tasks, SSM will fire the task and disconnect
This makes the task **fail**, but the process will still run on the target host.
```json { "changed": false, "module_stderr": "", "module_stdout": "\u001b]0;@ip-172-31-42-42:/usr/bin\u0007{\"failed\": 0, \"started\": 1, \"finished\": 0, \"ansible_job_id\": \"j604343782826.4885\", \"results_file\": \"/tmp/.ansible-ssm-user/async/j604343782826.4885\", \"_ansible_suppress_tmpdir_delete\": true}\r\r", "msg": "MODULE FAILURE\nSee stdout/stderr for the exact error", "rc": 0 } ```
Fire these tasks with `poll` set to `0` and forcing a specific failure test.
Then, use a different task to check up on them. > When checking up tasks with `ansible.builtin.async_status`, SSM will use a single connection.
> Said connection must be kept alive until the end of the task.
```yaml - name: Dump a DB from an RDS instance vars: ansible_connection: community.aws.aws_ssm ansible_remote_tmp: /tmp/.ansible-ssm-user/tmp #-- see previous gotchas ansible_async_dir: /tmp/.ansible-ssm-user/async #-- see previous gotchas wanted_pattern_in_module_output: >- {{ '"failed": 0, "started": 1, "finished": 0' | regex_escape() }} community.postgresql.postgresql_db: { … } async: "{{ 60 * 60 * 2 }}" #-- wait up to 2 hours ( 60s * 60m * 2h ) poll: 0 #-- fire and forget; ssm would not allow self-checking anyways register: dump changed_when: - dump.rc == 0 - dump.module_stderr == '' - "'started' | extract(dump.module_stdout | regex_search('{.*}') | from_json) == 1" - "'failed' | extract(dump.module_stdout | regex_search('{.*}') | from_json) == 0" failed_when: dump.rc != 0 #-- specify the failure yourself - name: Check on the dump task vars: max_wait: "{{ 60 * 60 * 2 }}" #-- wait for the async task to end ansible_aws_ssm_timeout: "{{ max_wait }}" #-- keep active the ssm connection the whole time ansible_remote_tmp: /tmp/.ansible-ssm-user/tmp #-- see previous gotchas ansible_async_dir: /tmp/.ansible-ssm-user/async #-- see previous gotchas dump_stdout_as_obj: "{{ dump.module_stdout | regex_search('{.*}') | from_json }}" ansible_job_id: "{{ dump_stdout_as_obj.ansible_job_id }}" ansible.builtin.async_status: jid: "{{ ansible_job_id }}" register: dump_result until: dump_result.finished retries: "{{ (max_wait/60) | int }}" #-- ( ( ( max_wait/60s ) * 1/( delay/60s ) ) | int ) delay: 60 #-- set high to avoid overloading the ssm agent with sessions ```
## Troubleshooting Refer [Troubleshooting managed node availability]. 1. Check the [Requirements] are satisfied. 1. [Check node availability using `ssm-cli`][check node availability using ssm-cli]. ### Check node availability using `ssm-cli` Refer [Troubleshooting managed node availability using `ssm-cli`][troubleshooting managed node availability using ssm-cli]. From the managed instance: ```sh $ sudo dnf -y install 'amazon-ssm-agent' $ sudo systemctl enable --now 'amazon-ssm-agent.service' $ sudo ssm-cli get-diagnostics --output 'table' ┌──────────────────────────────────────┬─────────┬─────────────────────────────────────────────────────────────────────┐ │ Check │ Status │ Note │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ EC2 IMDS │ Success │ IMDS is accessible and has instance id i-0123456789abcdef0 in │ │ │ │ region eu-west-1 │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Hybrid instance registration │ Skipped │ Instance does not have hybrid registration │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to ssm endpoint │ Success │ ssm.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to ec2messages endpoint │ Success │ ec2messages.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to ssmmessages endpoint │ Success │ ssmmessages.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to s3 endpoint │ Success │ s3.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to kms endpoint │ Success │ kms.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to logs endpoint │ Success │ logs.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Connectivity to monitoring endpoint │ Success │ monitoring.eu-west-1.amazonaws.com is reachable │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ AWS Credentials │ Success │ Credentials are for │ │ │ │ arn:aws:sts::012345678901:assumed-role/managed/i-0123456789abcdef0 │ │ │ │ and will expire at 2024-04-22 18:19:48 +0000 UTC │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Agent service │ Success │ Agent service is running and is running as expected user │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ Proxy configuration │ Skipped │ No proxy configuration detected │ ├──────────────────────────────────────┼─────────┼─────────────────────────────────────────────────────────────────────┤ │ SSM Agent version │ Success │ SSM Agent version is 3.3.131.0 which is the latest version │ └──────────────────────────────────────┴─────────┴─────────────────────────────────────────────────────────────────────┘ ``` ## Further readings - [Amazon Web Services] - AWS' [CLI] - [Ansible] - [EC2] ### Sources - [Start a session] - [Using Ansible in AWS] - [How can i change the session manager shell to BASH on EC2 linux instances?] - [Using Ansible in AWS] - [Troubleshooting managed node availability] - [Troubleshooting managed node availability using `ssm-cli`][troubleshooting managed node availability using ssm-cli] [check node availability using ssm-cli]: #check-node-availability-using-ssm-cli [gotchas]: #gotchas [requirements]: #requirements [ansible]: ../../ansible.md [amazon web services]: README.md [cli]: cli.md [ec2]: ec2.md [snippets]: ../../../snippets/aws/ [amazon.aws.aws_ec2 inventory]: https://docs.ansible.com/ansible/latest/collections/amazon/aws/aws_ec2_inventory.html [aws_ssm connection plugin notes]: https://docs.ansible.com/ansible/latest/collections/community/aws/aws_ssm_connection.html#notes [community.aws.aws_ssm connection]: https://docs.ansible.com/ansible/latest/collections/community/aws/aws_ssm_connection.html [session manager preferences]: https://console.aws.amazon.com/systems-manager/session-manager/preferences [start a session]: https://docs.aws.amazon.com/systems-manager/latest/userguide/session-manager-working-with-sessions-start.html [troubleshooting managed node availability using ssm-cli]: https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-cli.html [troubleshooting managed node availability]: https://docs.aws.amazon.com/systems-manager/latest/userguide/troubleshooting-managed-instances.html [ansible temp dir change]: https://devops.stackexchange.com/questions/10703/ansible-temp-dir-change [how can i change the session manager shell to bash on ec2 linux instances?]: https://repost.aws/knowledge-center/ssm-session-manager-change-shell [using ansible in aws]: https://rhuaridh.co.uk/blog/ansible-in-aws.html