[System logs]: Improvements to prevent filling /var/log partition

[jleveque]

• Force log rotation at size thresholds only (no longer also rotating logs daily), allowing for more consistent archived log size
• Eliminate remaining duplicate log messages
• Cron facility now only logs to cron.log (was also logging to syslog)
• Debug, mail, news and user log facilities only log to syslog; no longer creating separate log files for these facilities
• Cron job that calls logrotate every minute now uses the main /etc/logrotate.conf file so as to check/rotate all logs every minute, not just the logs specified in the rsyslog file. Also redirecting output of this command to /dev/null to prevent "(CRON) info (No MTA installed, discarding output)" messages in cron.log due to lack of a mail service
• Delete archive files based on remaining /var/log partition space. Note that this solution currently requires a minimum /var/log partition size of 32MB to function correctly
• Update sonic-sairedis and sonic-swss submodules to incorporate recording file name changes
• Add .screen file to .gitignore (unrelated)

[lguohan]

I wonder if 1M would be better, resulting less log files.

[jleveque]

I agree it would result in less log files total. However, I was trying to find a balance between reasonable log file size and supporting as small a partition as possible, while also maximizing the used space of smaller partitions.

Increasing the file size to 1M will increase the minimum /var/log partition size to ~32MB, but will require that we maintain ~20MB free space to ensure we always keep at least one archived copy of each log and have enough free space to potentially fill all logs before the next rotation (vs. a minimum partition size of ~18MB maintaining ~12MB free space with 512k files). If you don't see a problem with this, I will make the change and test it ASAP.