Recently when a Linux monitoring script using CURL to monitor a https URL broke when migrated to a VM from Oracle Linux v6.7 to v6.9. This post i will try to explain the root cause of the issue and solution to fix the issue.
Postfix a way to limit the frequency of brute force?
In file /usr/local/etc/postfix/main.cf place something like the following:
# RATE THROTTLING
smtpd_client_connection_rate_limit = 20
smtpd_error_sleep_time = 10s
smtpd_soft_error_limit = 3
smtpd_hard_error_limit = 5
To simply view the logs on your system, you can execute the following command:
This will display the logs with the oldest entries first. Although this is simple, it is not very useful since we do not tend to read logs like a book.
By default journalctl displays the logs in a pager. It shows you one page of logs requiring you to hit the space bar to proceed.
Diplaying Logs by Date Read More
The answer to the question of “how do I upgrade?” is always “it depends”, because everyone’s situation is going to be slightly different. This blog will cover some of the most straightforward ways which should apply in the majority of cases.
Either of the following two methods would work in most circumstances:
Backing up and restoring the existing configuration to a new installation
Maintaining completely separate domain and node directories and pointing the new version to the existing directories Read More
The maillog is easy enough to follow, but when you understand what all the delay and delays numbers mean then this may help really understand what is going on!
A standard email entry in postfix looks like:
Jan 10 10:00:00 testmtr postfix/smtp: 34A1B160852B: to=, relay=mx1.example.lan[18.104.22.168]:25, delay=0.49, delays=0.2/0/0.04/0.25, dsn=2.0.0, status=sent