Check Mail Server Certificate with openssl
You applied a new certificate to you mail server. Now you want to know, if the right certificate with the matching chain is used: openssl s_client -starttls smtp -showcerts -connect…
Posts related to Linux
Create a Centos Repository Mirror
Quite a few companies do not allow direct connections from the internal servers to the Internet. This is usually no problem, beside the time, when you want to update your…
Using Apple Mac Keyboard with Ubuntu
You are a Mac user and run Linux machines virtually on your Macbook or your console keyboard is an Apple Mac Keyboard. Ubuntu Linux sets the keyboard parameters in the…
Use netcat instead of telnet
Network engineers often use telnet to establish a connection to a service on a remote server. Apple dropped the telnet and ftp client in macOS High Sierra. First I was…
Hide your version of BIND
To hide your version of bind, enter the following value to your named.conf version "[NONE]"; in the option section: options { directory "/var/lib/bind"; version "[NONE]"; }; Check the value with…
pcap filter
tcpdump and ngrep are both based on libpcap. Therefore both use the same filter expressions. Here is the manual page of the ⇒pcap filter expression. These filter expressions are also…