How do I get help?¶
Having trouble? We would like to help!
Where are the logs?¶
Cloud-init uses two files to log to:
- /var/log/cloud-init-output.log: captures the output from each stage of cloud-init when it runs
- /var/log/cloud-init.log: very detailed log with debugging output, detailing each action taken
- /run/cloud-init: contains logs about how cloud-init decided to enable or disable itself, as well as what platforms/datasources were detected. These logs are most useful when trying to determine what cloud-init ran or did not run.
Be aware that each time a system boots, new logs are appended to the files in /var/log. Therefore, the files may have more than one boot worth of information present.
When reviewing these logs look for any errors or Python tracebacks to check for any errors.
Where are the configuration files?¶
Cloud-init config is provided in two places:
These files can define the modules that run during instance initialization, the datasources to evaluate on boot, and other settings.
Where are the data files?¶
Inside the /var/lib/cloud/ directory there are two important subdirectories:
The /var/lib/cloud/instance directory is a symbolic link that points to the most recenlty used instance-id directory. This folder contains the information cloud-init received from datasources, including vendor and user data. This can be helpful to review to ensure the correct data was passed.
It also contains the datasource file that containers the full information about what datasource was identified and used to setup the system.
Finally, the boot-finished file is the last thing that cloud-init does.
The /var/lib/cloud/data directory contain information related to the previous boot:
- instance-id: id of the instance as discovered by cloud-init. Changing this file has no effect.
- result.json: json file will show both the datasource used to setup the instance, and if any errors occured
- status.json: json file shows the datasource used and a break down of all four modules if any errors occured and the start and stop times.
What datasource am I using?¶
To correctly setup an instance, cloud-init must correctly identify the cloud that it is on. Therefore knowing what datasource is used on an instance launch can help aid in debugging.
To find what datasource is getting used run the cloud-id command:
$ cloud-id nocloud
If the cloud-id is not what is expected, then running the ds-identify script in debug mode and providing that in a bug can help aid in resolving any issues:
$ sudo DEBUG_LEVEL=2 DI_LOG=stderr /usr/lib/cloud-init/ds-identify --force
The force parameter allows the command to be run again since the instance has already launched. The other options increase the verbosity of logging and put the logs to STDERR.
How can I debug my user data?¶
Two of the most common issues with user data, that also happens to be cloud-config is:
- Incorrectly formatted YAML
- First line does not contain #cloud-config
To verify your YAML, we do have a short script called validate-yaml.py that can validate your user data offline.
Another option is to run the following on an instance when debugging:
$ sudo cloud-init query userdata > user-data.yaml $ cloud-init devel schema -c user-data.yaml --annotate
As launching instances in the cloud can cost money and take a bit longer, sometimes it is easier to launch instances locally using Multipass or LXD:
Multipass is a cross-platform tool to launch Ubuntu VMs across Linux, Windows, and macOS.
When a user launches a Multipass VM, user data can be passed by adding the –cloud-init flag and the appropriate YAML file containing user data:
$ multipass launch bionic --name test-vm --cloud-init userdata.yaml
Multipass will validate the YAML syntax of the cloud-config file before attempting to start the VM! A nice addition to help save time when experimenting with launching instances with various cloud-configs.
Multipass only supports passing user-data and only as YAML cloud-config files. Passing a script, a MIME archive, or any of the other user-data formats cloud-init supports will result in an error from the YAML syntax validator.
LXD offers a streamlined user experience for using linux system containers. With LXD, a user can pass:
- user data
- vendor data
- network configuration
The following initializes a container with user data:
$ lxc init ubuntu-daily:bionic test-container $ lxc config set test-container user.user-data - < userdata.yaml $ lxc start test-container
To avoid the extra commands this can also be done at launch:
$ lxc launch ubuntu-daily:bionic test-container --config=user.user-data="$(cat userdata.yaml)"
Finally, a profile can be setup with the specific data if a user needs to launch this multiple times:
$ lxc profile create dev-user-data $ lxc profile set dev-user-data user.user-data - < cloud-init-config.yaml $ lxc launch ubuntu-daily:bionic test-container -p default -p dev-user-data
The above examples all show how to pass user data. To pass other types of configuration data use the config option specified below:
Where can I learn more?¶
Below are some videos, blog posts, and white papers about cloud-init from a variety of sources.
- Cloud Instance Initialization with cloud-init (Whitepaper)
- cloud-init Summit 2018
- cloud-init - The cross-cloud Magic Sauce (PDF)
- cloud-init Summit 2017
- cloud-init - Building clouds one Linux box at a time (Video)
- cloud-init - Building clouds one Linux box at a time (PDF)
- Metadata and cloud-init
- The beauty of cloud-init
- Introduction to cloud-init