socklog-overlay

The socklog-overlay is an add-on for the s6-overlay - it provides a small syslog replacement based on Gerrit Pape's socklog.

Usage

Installation is similar to installing the s6-overlay:

FROM ubuntu

# Install s6-overlay
ADD https://github.com/just-containers/s6-overlay/releases/download/v1.21.8.0/s6-overlay-amd64.tar.gz /tmp/
RUN tar xzf /tmp/s6-overlay-amd64.tar.gz -C /

# Install socklog-overlay
ADD https://github.com/just-containers/socklog-overlay/releases/download/v3.1.0-2/socklog-overlay-amd64.tar.gz /tmp/
RUN tar xzf /tmp/socklog-overlay-amd64.tar.gz -C /

ENTRYPOINT ["/init"]

This will run a logging service with all messages in directories under /var/log/socklog/, with built-in log rotation.

• /var/log/socklog/cron
• /var/log/socklog/daemon
• /var/log/socklog/debug
• /var/log/socklog/errors
• /var/log/socklog/everything
• /var/log/socklog/kernel
• /var/log/socklog/mail
• /var/log/socklog/messages
• /var/log/socklog/secure
• /var/log/socklog/user

Customization

Custom logging rules

socklog-overlay works by reading in a series of s6-log logging scripts from /etc/socklog.rules. You can create your own rules by placing a file in /etc/socklog.rules. Each directive (selection directive, control directive, or action directive) for the logging script should be on its own line.

For example, if you wanted to save all errors for messages tagged with the "local0" facility, you could create the file /etc/socklog.rules/local0-error

-
+^local0\.err
T
/var/log/socklog/local0-errors

This will match lines that begin with local0.err, prepend them with an ISO8601 timestamp, and save them to the /var/log/socklog/local0-errors folder.

Another example, if you wanted to have all syslog messages copied to stdout, create a file at /etc/socklog.rules/forward-stdout:

+
1

This will match all lines (as indicated by the + symbol with an empty regex), and forward them to stdout (indicated by the 1 symbol).

More details on how to write s6-log logging scripts are available in the s6-log manual.

Creating logging folders

The /etc/cont-init.d/~-socklog script should run last, and its final step is to recursively chown /var/log/socklog.

Create a script in /etc/cont-init.d to make your needed logging folder, if it's a subfolder of /var/log/socklog, you should be covered. If not, you'll likely need to chown it as well, to the nobody user.

Environment variables

• SOCKLOG_TIMESTAMP_FORMAT - controls how (or if) a timestamp should be placed before every line, defaults to T
  • (empty) - do not insert timestamps into logs
  • T - prepend every line with an ISO 8601 timestamp
  • t - prepend every line with a TAI64N timestamp

Ideas I'd like to flesh out:

• Setting an environment variable to specify number of files, size, etc
  • Right now this is just using the s6-log defaults - 10 files, ~100k per file

Verifying Downloads

The socklog-overlay releases are signed using gpg, you can import our public key:

$ curl https://keybase.io/justcontainers/key.asc | gpg --import

Then verify the downloaded files:

$ gpg --verify socklog-overlay-amd64.tar.gz.sig socklog-overlay-amd64.tar.gz

Upgrade Notes

3.0.0

socklog-overlay version 3.0.0 switched from having the hard-coded log/run script with log pattern rules, to using the /etc/socklog.rules folder. If you have a custom log/run script, it should continue to work.

3.1.0

Added the SOCKLOG_TIMESTAMP_FORMAT environment variable.

LICENSE

ISC license, see LICENSE.md

Binary downloads include a copy of socklog, which is released under a 3-clause BSD license. Please see COPYING for details.