I have a server on a LAN that need to send emails. Of course, this server has access to the internet through NAT, but for emails it is a bit more difficult : nowadays, email servers are checking many things when receiving emails : reverse, ‘from’ field, etc. and you may not have access to this kind of tuning for the internet IP address used with your NAT. So I needed to configure a relayhost, with direct access to the internet, that would accept my incoming email and relay it through normal channels. But I don’t want this server to be an open relay, so I have to setup authentication between them.
Today I will talk about auditd, a very powerfull tool to debug anything you need in a linux platform. In this very case, I had a problem with a mail server using all IO available. ‘iostat’ command told me it was reads ops that saturate it. A mail server has many process, so using “strace” is not helpful here. I choose to use auditd.
When you type ‘lvs’ on Linux, you get a list of logical volume system with their attributse as a single letter : /// LV VG Attr LSize Origin Snap% Move Log Copy% Convert lv_hdd hdd -wi-a- 232.00g /// We’ll explain all attr fields in this post.
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