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53 lines
2.9 KiB
Markdown
53 lines
2.9 KiB
Markdown
---
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title: Built-in System Services in RancherOS
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redirect_from:
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- os/v1.1/en/system-services/built-in-system-services/
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---
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## Built-in System Services
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To launch RancherOS, we have built-in system services. They are defined in the [Docker Compose](https://docs.docker.com/compose/compose-file/) format, and can be found in the default system config file, `/usr/share/ros/os-config.yml`. You can [add your own system services]({{page.osbaseurl}}/system-services/) or override services in the cloud-config.
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### preload-user-images
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Read more about [image preloading]({{page.osbaseurl}}/boot-process/image-preloading/).
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### network
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During this service, networking is set up, e.g. hostname, interfaces, and DNS.
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It is configured by `hostname` and `rancher.network`[settings]({{page.osbaseurl}}/networking/) in [cloud-config]({{page.osbaseurl}}/configuration/#cloud-config).
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### ntp
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Runs `ntpd` in a System Docker container.
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### console
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This service provides the RancherOS user interface by running `sshd` and `getty`. It completes the RancherOS configuration on start up:
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1. If the `rancher.password=<password>` kernel parameter exists, it sets `<password>` as the password for the `rancher` user.
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2. If there are no host SSH keys, it generates host SSH keys and saves them under `rancher.ssh.keys` in [cloud-config]({{page.osbaseurl}}/configuration/#cloud-config).
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3. Runs `cloud-init -execute`, which does the following:
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* Updates `.ssh/authorized_keys` in `/home/rancher` and `/home/docker` from [cloud-config]({{page.osbaseurl}}/configuration/ssh-keys/) and metadata.
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* Writes files specified by the `write_files` [cloud-config]({{page.osbaseurl}}/configuration/write-files/) setting.
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* Resizes the device specified by the `rancher.resize_device` [cloud-config]({{page.osbaseurl}}/configuration/resizing-device-partition/) setting.
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* Mount devices specified in the `mounts` [cloud-config]({{page.osbaseurl}}/configuration/additional-mounts/) setting.
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* Set sysctl parameters specified in the`rancher.sysctl` [cloud-config]({{page.osbaseurl}}/configuration/sysctl/) setting.
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4. If user-data contained a file that started with `#!`, then a file would be saved at `/var/lib/rancher/conf/cloud-config-script` during cloud-init and then executed. Any errors are ignored.
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5. Runs `/opt/rancher/bin/start.sh` if it exists and is executable. Any errors are ignored.
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6. Runs `/etc/rc.local` if it exists and is executable. Any errors are ignored.
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### docker
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This system service runs the user docker daemon. Normally it runs inside the console system container by running `docker-init` script which, in turn, looks for docker binaries in `/opt/bin`, `/usr/local/bin` and `/usr/bin`, adds the first found directory with docker binaries to PATH and runs `dockerlaunch docker daemon` appending the passed arguments.
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Docker daemon args are read from `rancher.docker.args` cloud-config property (followed by `rancher.docker.extra_args`).
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