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System logging notes in README.md

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Ryan Sundberg
2017-10-31 14:16:27 -07:00
parent 91363dcf37
commit 70b5c73902
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README.md
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@@ -57,6 +57,7 @@ You can configure the stock `ubuntu` image yourself from your Dockerfile, so why
* [Environment variable dumps](#envvar_dumps) * [Environment variable dumps](#envvar_dumps)
* [Modifying environment variables](#modifying_envvars) * [Modifying environment variables](#modifying_envvars)
* [Security](#envvar_security) * [Security](#envvar_security)
* [System Logging](#logging)
* [Upgrading the operating system inside the container](#upgrading_os) * [Upgrading the operating system inside the container](#upgrading_os)
* [Container administration](#container_administration) * [Container administration](#container_administration)
* [Running a one-shot command in a new container](#oneshot) * [Running a one-shot command in a new container](#oneshot)
@@ -302,6 +303,14 @@ If you are sure that your environment variables don't contain sensitive data, th
RUN chmod 755 /etc/container_environment RUN chmod 755 /etc/container_environment
RUN chmod 644 /etc/container_environment.sh /etc/container_environment.json RUN chmod 644 /etc/container_environment.sh /etc/container_environment.json
<a name="logging"></a>
### System Logging
Baseimage-docker uses syslog-ng to provide a syslog facility to the container. Syslog-ng is not managed as an runit service (see below). Syslog messages are forwarded to the console via the service at /etc/service/syslog-forwarder.
#### Log startup/shutdown sequence
In order to ensure that all application log messages are captured by syslog-ng, syslog-ng is started separately before the runit supervisor process, and shutdown after runit exits. This uses the [startup script facility](#running_startup_scripts) provided by this image. This avoids a race condition which would exist if syslog-ng were managed as an runit service, where runit kills syslog-ng in parallel with the container's other services, causing log messages to be dropped during a graceful shutdown if syslog-ng exits while logs are still being produced by other services.
<a name="upgrading_os"></a> <a name="upgrading_os"></a>
### Upgrading the operating system inside the container ### Upgrading the operating system inside the container