When you boot instances in an OpenStack cloud, you can use user data or cloud-init to automatically configure instances at boot time. You might want to install some packages, start services, or manage your instance by using a Puppet or Chef server. User data is the mechanism by which a user can pass information contained in a local file to an instance at launch time. The typical use case is to pass something like a shell script or a configuration file as user data. User data is sent using the --user-data /path/to/filename option when calling nova boot. This example creates a text file and sends its contents as user data to the instance: $ echo "This is some text" > myfile.txt $ nova boot --user-data ./myfile.txt --image myimage myinstance The instance can get user data by querying the metadata service through either the OpenStack metadata API or the EC2 compatibility API: $ curl http://169.254.169.254/2009-04-04/user-data This is some text $ curl http://169.254.169.254/openstack/2012-08-10/user_data This is some text The Compute service treats user data as a blob. While the previous example uses a text file, user data can be in any format. For more information, see . To do something useful with the user data, you must configure the virtual machine image to run a service on boot that gets user data from the metadata service and takes some action based on the contents of the data. The cloud-init package does exactly this. This package is compatible with the Compute metadata service and the Compute configuration drive. The cloud-init package supports multiple cloud providers. You can use the same virtual machine image in different clouds without modification. The cloud-init package is an open source project and the source code is available on Launchpad. It is maintained by Canonical, the company that runs the Ubuntu project. All Ubuntu cloud images come pre-installed with cloud-init. However, cloud-init is not designed to be Ubuntu-specific and has been successfully ported to several other platforms including Fedora. Even if you do not use user data to configure instance behavior at boot time, install cloud-init on images that you create because this package provides useful functionality. For example, the cloud-init package enables you to copy the public key to an account (the ubuntu account by default on Ubuntu instances, the ec2-user by default in Fedora instances). If you do not have cloud-init installed, you must manually configure your image to get the public key from the metadata service on boot and copy it to the appropriate account. Look at the cloud-init doc/userdata.txt file the examples directory and the Ubuntu community documentation for details about how to use cloud-init. Some basic examples are provided here. cloud-init supports several input formats for user data. Two commonly used formats are: Shell scripts (starts with #!) Cloud config files (starts with #cloud-config) Assuming you have cloud-init installed, the simplest way to configure an instance on boot is to pass a shell script as user data. The shell file must begin with #! in order for cloud-init to recognize it as a shell script. This example shows a script that creates a clouduser account: #!/bin/bash adduser --disabled-password --gecos "" clouduser Sending a shell script as user data has a similar effect to writing an /etc/rc.local script: it executes very late in the boot sequence as root. cloud-init supports a YAML-based config format that allows the user to configure a large number of options on a system. User data that begins with #cloud-config will be interpreted by cloud-init as cloud-config format. This cloud-init user data example sets the hostname and the FQDN, as well as updating /etc/hosts on the instance: #cloud-config hostname: mynode fqdn: mynode.example.com manage_etc_hosts: true This cloud-init user data example, based on doc/examples/cloud-config-puppet.txt, would configure the instance to contact a Puppet server at puppetmaster.example.org and verify its identity by using a certificate. #cloud-config puppet: conf: agent: server: "puppetmaster.example.org" ca_cert: | -----BEGIN CERTIFICATE----- MIICCTCCAXKgAwIBAgIBATANBgkqhkiG9w0BAQUFADANMQswCQYDVQQDDAJjYTAe Fw0xMDAyMTUxNzI5MjFaFw0xNTAyMTQxNzI5MjFaMA0xCzAJBgNVBAMMAmNhMIGf MA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCu7Q40sm47/E1Pf+r8AYb/V/FWGPgc b014OmNoX7dgCxTDvps/h8Vw555PdAFsW5+QhsGr31IJNI3kSYprFQcYf7A8tNWu 1MASW2CfaEiOEi9F1R3R4Qlz4ix+iNoHiUDTjazw/tZwEdxaQXQVLwgTGRwVa+aA qbutJKi93MILLwIDAQABo3kwdzA4BglghkgBhvhCAQ0EKxYpUHVwcGV0IFJ1Ynkv T3BlblNTTCBHZW5lcmF0ZWQgQ2VydGlmaWNhdGUwDwYDVR0TAQH/BAUwAwEB/zAd BgNVHQ4EFgQUu4+jHB+GYE5Vxo+ol1OAhevspjAwCwYDVR0PBAQDAgEGMA0GCSqG SIb3DQEBBQUAA4GBAH/rxlUIjwNb3n7TXJcDJ6MMHUlwjr03BDJXKb34Ulndkpaf +GAlzPXWa7bO908M9I8RnPfvtKnteLbvgTK+h+zX1XCty+S2EQWk29i2AdoqOTxb hppiGMp0tT5Havu4aceCXiy2crVcudj3NFciy8X66SoECemW9UYDCb9T5D0d -----END CERTIFICATE----- This cloud-init user data example, based on doc/examples/cloud-config/chef.txt and intended for use in an Ubuntu image, adds the Chef apt repository, installs Chef, connects to a Chef server at https://chefserver.example.com/organizations/myorg/, and installs Apache: #cloud-config apt_sources: - source: "deb https://packagecloud.io/chef/ stable main" key: | -----BEGIN PGP PUBLIC KEY BLOCK----- Version: GnuPG v1.4.9 (GNU/Linux) mQINBFLUbogBEADceEoxBDoE6QM5xV/13qiELbFIkQgy/eEi3UesXmJblFdU7wcD LOW3NuOIx/dgbZljeMEerj6N1cR7r7X5sVoFVEZiK4RLkC3Cpdns0d90ud2f3VyK K7PXRBstdLm3JlW9OWZoe4VSADSMGWm1mIhT601qLKKAuWJoBIhnKY/RhA/RBXt7 z22g4ta9bT67PlliTo1a8y6DhUA7gd+5TsVHaxDRrzc3mKObdyS5LOT/gf8Ti2tY BY5MBbQ8NUGExls4dXKlieePhKutFbde7sq3n5sdp1Ndoran1u0LsWnaSDx11R3x iYfXJ6xGukAc6pYlUD1yYjU4oRGhD2fPyuewqhHNUVwqupTBQtEGULrtdwK04kgI H93ssGRsLqUKe88uZeeBczVuupv8ZLd1YcQ29AfJHe6nsevsgjF+eajYlzsvC8BN q3nOvvedcuI6BW4WWFjraH06GNTyMAZi0HibTg65guZXpLcpPW9hTzXMoUrZz8Mv J9yUBcFPKuFOLDpRP6uaIbxJsYqiituoltl0vgS/vJcpIVVRwSaqPHa6S63dmKm2 6gq18v4l05mVcInPn+ciHtcSlZgQkCsRTSvfUrK+7nzyWtNQMGKstAZ7AHCoA8Pb c3i7wyOtnTgfPFHVpHg3JHsPXKk9/71YogtoNFoETMFeKL1K+O+GMQddYQARAQAB tDdwYWNrYWdlY2xvdWQgb3BzIChwcm9kdWN0aW9uIGtleSkgPG9wc0BwYWNrYWdl Y2xvdWQuaW8+iQI+BBMBAgAoBQJS1G6IAhsvBQkJZgGABgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgAAKCRDC5zQk1ZCXq13KD/wNzAi6rEzRyx6NH61Hc19s2QAgcU1p 1mX1Tw0fU7CThx1nr8JrG63465c9dzUpVzNTYvMsUSBJwbb1phahCMNGbJpZRQ5b vW/i3azmk/EHKL7wgMV8wu1atu6crrxGoDEfWUa4aIwbxZGkoxDZKZeKaLxz2ZCh uKzjvkGUk4PUoOxxPn9XeFmJQ68ys4Z0CgIGfx2i64apqfsjVEdWEEBLoxHFIPy7 FgFafRL0bgsquwPkb5q/dihIzJEZ2EMOGwXuUaKI/UAhgRIUGizuW7ECEjX4FG92 8RsizHBjYL5Gl7DMt1KcPFe/YU/AdWEirs9pLQUr9eyGZN7HYJ03Aiy8R5aMBoeY sfxjifkbWCpbN+SEATaB8YY6Zy2LK/5TiUYNUYb/VHP//ZEv0+uPgkoro6gWVkvG DdXqH2d9svwfrQKfGSEQYXlLytZKvQSDLAqclSANs/y5HDjUxgtWKdsL3xNPCmff jpyiqS4pvoTiUwS4FwBsIR2sBDToIEHDvTNk1imeSmxCUgDxFzWkmB70FBmwz7zs 9FzuoegrAxXonVit0+f3CxquN7tS0mHaWrZfhHxEIt65edkIz1wETOch3LIg6RaF wsXgrZCNTB/zjKGAFEzxOSBkjhyJCY2g74QNObKgTSeGNFqG0ZBHe2/JQ33UxrDt peKvCYTbjuWlyrkCDQRS1G6IARAArtNBXq+CNU9DR2YCi759fLR9F62Ec/QLWY3c /D26OqjTgjxAzGKbu1aLzphP8tq1GDCbWQ2BMMZI+L0Ed502u6kC0fzvbppRRXrV axBrwxY9XhnzvkXXzwNwnBalkrJ5Yk0lN8ocwCuUJohms7V14nEDyHgAB8yqCEWz Qm/SIZw35N/insTXshcdiUGeyufo85SFhCUqZ1x1TkSC/FyDG+BCwArfj8Qwdab3 UlUEkF6czTjwWIO+5vYuR8bsCGYKCSrGRh5nxw0tuGXWXWFlBMSZP6mFcCDRQDGc KOuGTjiWzLJcgsEcBoIX4WpHJYgl6ovex7HkfQsWPYL5V1FIHMlw34ALx4aQDH0d PJpC+FxynrfTfsIzPnmm2huXPGGYul/TmOp00CsJEcKOjqcrYOgraYkCGVXbd4ri 6Pf7wJNiJ8V1iKTzQIrNpqGDk306Fww1VsYBLOnrSxNPYOOu1s8c8c9N5qbEbOCt QdFf5pfuqsr5nJ0G4mhjQ/eLtDA4E7GPrdtUoceOkYKcQFt/yqnL1Sj9Ojeht3EN PyVSgE8NiWxNIEM0YxPyJEPQawejT66JUnTjzLfGaDUxHfseRcyMMTbTrZ0fLJSR aIH1AubPxhiYy+IcWOVMyLiUwjBBpKMStej2XILEpIJXP6Pn96KjMcB1grd0J2vM w2Kg3E8AEQEAAYkERAQYAQIADwUCUtRuiAIbLgUJCWYBgAIpCRDC5zQk1ZCXq8Fd IAQZAQIABgUCUtRuiAAKCRA3u+4/etlbPwI5D/4idr7VHQpou6c/YLnK1lmz3hEi kdxUxjC4ymOyeODsGRlaxXfjvjOCdocMzuCY3C+ZfNFKOTtVY4fV5Pd82MuY1H8l nuzqLxT6UwpIwo+yEv6xSK0mqm2FhT0JSQ7E7MnoHqsU0aikHegyEucGIFzew6BJ UD2xBu/qmVP/YEPUzhW4g8uD+oRMxdAHXqvtThvFySY/rakLQRMRVwYdTFHrvu3z HP+6hpZt25llJb3DiO+dTsv+ptLmlUr5JXLSSw2DfLxQa0kD5PGWpFPVJcxraS2p NDK9KTi2nr1ZqDxeKjDBT6zZOs9+4JQ9fepn1S26AmHWHhyzvpjKxVm4sOilKysi 84CYluNrlEnidNf9wQa3NlLmtvxXQfm1py5tlwL5rE+ek1fwleaKXRcNNmm+T+vD dIw+JcHy8a53nK1JEfBqEuY6IqEPKDke0wDIsDLSwI1OgtQoe7Cm1PBujfJu4rYQ E+wwgWILTAgIy8WZXAloTcwVMtgfSsgHia++LqKfLDZ3JuwpaUAHAtguPy0QddvF I4R7eFDVwHT0sS3AsG0HAOCY/1FRe8cAw/+9Vp0oDtOvBWAXycnCbdQeHvwh2+Uj 2u2f7K3CDMoevcBl4L5fkFkYTkmixCDy5nst1VM5nINueUIkUAJJbOGpd6yFdif7 mQR0JWcPLudb+fwusJ4UEACYWhPa8Gxa7eYopRsydlcdEzwpmo6E+V8GIdLFRFFp KHQEzbSW5coxzU6oOiPbTurCZorIMHTA9cpAZoMUGKaSt19UKIMvSqtcDayhgf4c Z2ay1z0fdJ2PuLeNnWeiGyfq78q6wqSaJq/h6JdAiwXplFd3gqJZTrFZz7A6Q6Pd 7B+9PZ/DUdEO3JeZlHJDfRmfU2XPoyPUoq79+whP5Tl3WwHUv7Fg357kRSdzKv9D bgmhqRHlgVeKn9pwN4cpVBN+idzwPefQksSKH4lBDvVr/9j+V9mmrOx7QmQ5LCc/ 1on+L0dqo6suoajADhKy+lDQbzs2mVb4CLpPKncDup/9iJbjiR17DDFMwgyCoy5O HJICQ5lckNNgkHTS6Xiogkt28YfK4P3S0GaZgIrhKQ7AmO3O+hB12Zr+olpeyhGB OpBD80URntdEcenvfnXBY/BsuAVbTGXiBzrlBEyQxg656jUeqAdXg+nzCvP0yJlB UOjEcwyhK/U2nw9nGyaR3u0a9r24LgijGpdGabIeJm6O9vuuqFHHGI72pWUEs355 lt8q1pAoJUv8NehQmlaR0h5wcwhEtwM6fiSIUTnuJnyHT053GjsUD7ef5fY1KEFm aZeW04kRtFDOPinz0faE8hvsxzsVgkKye1c2vkXKdOXvA3x+pZzlTHtcgMOhjKQA sA== =H60S -----END PGP PUBLIC KEY BLOCK----- chef: install_type: "packages" server_url: "https://chefserver.example.com/organizations/myorg/" node_name: "your-node-name" environment: "production" validation_name: "yourorg-validator" validation_key: | -----BEGIN RSA PRIVATE KEY----- YOUR-ORGS-VALIDATION-KEY-HERE -----END RSA PRIVATE KEY----- run_list: - "recipe[apache2]" - "role[db]" initial_attributes: apache: prefork: maxclients: 100 keepalive: "off"