Some days ago I experienced weird problem with my Enigmail in Icedove e-mail client. When I tried send signed or encrypted message I saw the following error message:

“GnuPG reported an error in the communication with gpg-agent (a component of GnuPG).”

Problem is caused by compatibility issues betwwen GnuPG and Enigmail plugin.

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Suppose that you need second full functional Postfix instance on the same machine. You can edit ‘master.cf‘ file of course but this solution does not provide necessary¬†separation level. This tutorial describes how to start second Postfix instance with separate ‘/var/spool/postfix‘ directory (queues, sockets, pids etc.).

In first step you need to create separate working directory for another server instance. Let’s copy:

/var/spool/postfix directory to /var/spool/postfix2,

/etc/postfix directory to /etc/postfix2.

Next create a copy of /usr/lib/systemd/system/postfix.service (with new name ‘postfix2.service’) and change following lines in ‘[Service]‘ section. Continue Reading

Rsync is a very powerful¬† backup tool. It can significantly speed up backup process and minimize amount of data transferred during synchronization. In most cases rsync is used to make incremental backups, but it also has another interesting option which gives you ability to keeping old versions of files on backup server. Mentioned option is ‘–backup’ or simply ‘-b’. Continue Reading

Some kinds of software require only one format of SSL certificates. This is the way how you can convert certificates between two popular formats (PEM and DER).

Use ‘openssl’:

openssl x509 -inform DER -in der-cert.crt -outform PEM -out pem-cert.pem

And vice versa:

openssl x509 -inform PEM -in pem-cert.pem -outform DER -out der-cert.crt