36 lines
2.1 KiB
Markdown
36 lines
2.1 KiB
Markdown
# Attaching to STDIO or TTY
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The model for STDIO, TTY, and logging is a little different in containerd.
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Because of the various methods that consumers want on the logging side these types of decisions
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are pushed to the client.
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Containerd API is developed for access on a single host therefore many things like paths on the host system are acceptable in the API.
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For the STDIO model the client requesting to start a container provides the paths for the IO.
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## Logging
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If no options are specified on create all STDIO of the processes launched by containerd will be sent to `/dev/null`.
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If you want containerd to send the STDIO of the processes to a file, you can pass paths to the files in the create container method defined by this proto in the stdin, stdout, and stderr fields:
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```proto
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message CreateContainerRequest {
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string id = 1; // ID of container
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string bundlePath = 2; // path to OCI bundle
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string stdin = 3; // path to the file where stdin will be read (optional)
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string stdout = 4; // path to file where stdout will be written (optional)
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string stderr = 5; // path to file where stderr will be written (optional)
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string console = 6; // path to the console for a container (optional)
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string checkpoint = 7; // checkpoint name if you want to create immediate checkpoint (optional)
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}
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```
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## Attach
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In order to have attach like functionality for your containers you use the same API request but named pipes or fifos can be used to achieve this type of functionality.
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The default CLI for containerd does this if you specify the `--attach` flag on `create` or `start`.
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It will create fifos for each of the containers stdio which the CLI can read and write to.
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This can be used to create an interactive session with the container, `bash` for example, or to have a blocking way to collect the container's STDIO and forward it to your logging facilities.
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## TTY
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The tty model is the same as above only the client creates a pty and provides to other side to containerd in the create request in the `console` field.
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Containerd will provide the pty to the container to use and the session can be opened with the container after it starts.
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