My blog

Category: Linux

  • Postfix and greylisting

    Spam became a noticeable threat for the mail servers many years ago. No servers today could be running without being hardened against the spam: according to some reports up to 75% of all the email traffic is spam. It’s noticeable from network capacity, hardware and electricity consumption even if you run a small company mail…

  • Postfix mail server with DKIM

    Installation and configuration of the mail server (Mail Transfer Agent, MTA) is one of the typical tasks any system administrator faces. Here we will cover the task and by the end of the article will have CentOS 7 with Postfix mail server that listens to he 25 port (SMTP) and delivers messages for the selected…

  • Moved to Hetzner and CentOS 8

    Turns out I had lost my keys to the Oracle Cloud and the Oracle Cloud lost my PTR record somehow, so the Gmail started to junk and bounce my mail. I decided to go for a Faster.cz (who’s my home provider) VPS, but they had 8GB SSD as an option for a small host, which…

  • Fish shell MOTD with lolcat and cowsay

    Setting fish shell message of the day with all the crazy stuff you need for a daily work: Full version: https://gist.github.com/angstbear/a0499e955ecf282c06c4a7dd9cb8bd35

  • Get top LDAP leafs

    /usr/bin/ldapsearch -H ldaps://localhost -W -b “dc=example,dc=com” “(objectclass=*)” -LL -W -D “cn=Manager” -s one

  • Search for a package in Fedora Silverblue

    sudo podman run –rm fedora:30 dnf search Okay

  • Extract PEM certificates and keys from a shared NSS DB

    $ certutil -L -d . Certificate Nickname Trust Attributes SSL,S/MIME,JAR/XPI FreeIPA CA CT,C,C $ certutil -L -d . -a -n ‘FreeIPA CA’ > freeipa.crt The PEM certificate should now be stored in free-ipa.crt. To extract the PEM key from key3.db use certutil, pk12util and openssl. $ certutil -K -d . -a $ pk12util -o keys.p12…

  • Linux UX improvements

    Fish as a shell. I like the fact that out of the box it does what it should do and what I configure in Bash. And I like abbreviations. ripgrep which is faster grep Bat which is a way better cat  ??? lolcat!

  • List of bash tutorials

    Just not to forget http://mywiki.wooledge.org/BashGuide/Arrays

  • Simple fail2ban log file parcer

    I have written simple fail2ban log file parcer in Golang that finds banned IPs, makes a struct with date, time and IP and a map with IP as a key and count as a value. I am thinking of nmapping the values I’ve got and making a report out of them.