If you have some problems with package updates and apt-get return the message ‘The following packages have been kept back’ means that the packages have been retained and there are newer versions of the listed packages, which for some reason cannot be installed. (unfulfilled or changed or new dependencies) The solution: apt-get dist-upgrade -u Example:…
What is ALPN ? Application-Layer Protocol Negotiation (ALPN) is a Transport Layer Security (TLS) extension for application layer protocol negotiation. ALPN allows the application layer to negotiate which protocol should be performed over a secure connection in a manner which avoids additional round trips and which is independent of the application layer protocols. It is…
Built-in content inspection introduction Postfix supports a built-in filter mechanism that examines message header and message body content, one line at a time, before it is stored in the Postfix queue. The filter is usually implemented with POSIX or PCRE regular expressions, as described in the header_checks(5) manual page. The original purpose of the built-in…
What is TFO ? In computer networking, TCP Fast Open (TFO) is an extension to speed up the opening of successive Transmission Control Protocol (TCP) connections between two endpoints. It works by using a TFO cookie (a TCP option), which is a cryptographic cookie stored on the client and set upon the initial connection with…
I’m using the following tools to perform lossless image compression: jpegoptim – jpegoptim is a utility for optimizing JPEG files. It provides lossless optimization (based on optimizing the Huffman tables) and “lossy” optimization based on setting a maximum quality factor. optipng – OptiPNG is a PNG optimizer that recompresses the image files to a smaller…