Firefox doesn't trust some of the certifcate chains that Internet Explorer and Chrome DO trust, this results in Firefox giving a warning about invalid certificate.

The proper certificates are here:

https://support.comodo.com/index.php?/Default/Knowledgebase/Article/View/979/108/domain-validation-sha-2

 I've got a client running Veeam and they were unable to create backups of VMs which had disks hosted on a network share

The error was: Unable to create snapshot (Fileshare Provider;Microsoft Software Shadow Copy provider 1.0) (mode: Hyper-V child partition snapshot). Details: Provider [{89300202-3cec-4981-9171-19f59559e0f2}] does not support shadow copies of volume [\\NAS01\VIRTUALPCS\]. --tr:Failed to add volumes to the snapshot set. --tr:Failed to perform pre-backup tasks. 

What was the solution? 

 I ran into several snapshots where something went wrong during Initial replication - These snapshots you are unable to delete using Hyper-V manager. 

The solution required using PowerShell to remove the snapshots, which worked fine.  

 There are some situations where port mirroring is handy, like capturing packets, using ethereal or more modernly called wireshark (showing my age calling it ethereal).. 

This iseasy to do in a physical environment with port mirroring on your network switch, but in a virtual environment it's equally easy or perhaps even easier. 

Usually SQL Servers should be dedicated machines, but sometimes users interfere by wanting to run apps (web servers or other programs) on the same sql servers.

Doing so requires SQL to not allocate all of the memory of the machine, below is a quick YouTube video showing you where to tune the memory parameters on SQL Server to reduce memory pressure.. 

 Sometimes you just need a quick answer of how many emails go to each domain from your mail logs, this may help you..

You can use grep cut uniq and sort to make a very quick summary

# grep "spamd: identified" maillog | cut -d\) -f 2 | cut -d: -f 1 | cut -d@ -f 2 | sort | uniq -c

 Doing something in git I got this error:

fatal: core.bare and core.worktree do not make sense

The solution was easy, manually edit the config file and change bare = true to bare = false