When doing a major version upgrade on Debian Linux with PostgreSQL server installed (using Debian-provided packages), this always catches me: After the upgrade there will be two different PostgreSQL instances running, it won’t do an in-place upgrade for the database automatically. In order to get the existing database running on the newer PostgreSQL version, this […]
Tag: linux
Commanding Devices with Tmux
Let’s go right away to the question: How do I enter commands on two devices at the same time? One of the possible answers is: With tmux. My usual workflow to connect to the end devices is from a Linux host that has tmux installed. The situation can look for example like this: Before being […]
Configuring Hourly Log Rotation with Logrotate and Rsyslog
Logrotate runs daily by default on Debian Linux. It is scheduled to run at 00:00:00 with systemd: markku@logtest:~$ systemctl list-timers NEXT LEFT LAST PASSED UNIT ACTIVATES Mon 2023-11-20 00:00:00 EET 2h 20min left Sun 2023-11-19 00:00:17 EET 21h ago logrotate.timer logrotate.service … When you want logrotate to rotate files hourly, you need two changes: For […]
Tools for Debian Packages
Debian has been my primary Linux distribution of choice since 2003. That’s twenty years! How time flies! I haven’t ever worked as full-time server administrator but running and operating various kinds of systems have always been part of my skills, and it has made it possible for me to leverage wide range of tooling required […]
Python Versions
Even though I’ve used Python programming language on-and-off since about year 2000, I only started paying more attention to specific Python versions around 2016 when I gradually started using Python more seriously in devops. When dealing with different runtime environments it is crucial to know which features are available in which Python versions. This page […]
Using Tmux
A long time ago I discovered screen. It made it possible to start applications in Linux and then disconnecting the SSH session, without stopping the applications. It was magic: otherwise the the applications just terminated if the SSH connection was lost. Then I heard about tmux. It was like screen on steroids! I could split […]
Serial Console Server on Raspberry Pi
Short one: How to make a serial console server (or terminal server) with a Raspberry Pi and USB-serial adapter. Connect the serial port to whatever device you want to use for testing, and use any telnet-compatible client (like PuTTY) to connect to your Pi’s IP address and the configured port (2000, 3000 or 4000 in […]
Configuring SNMP Trap Receiver for Zabbix on Debian
In order to handle SNMP traps in Zabbix you need to configure your server to receive the traps. Here are the steps, tested with Zabbix 5.4 on Debian Linux 10 (Buster), assuming Zabbix server has already been installed from the official repository: (Note: Long commands and paths below can appear split incorrectly, so be careful […]
LDAPS Problem: Can’t contact LDAP server (-1)
LDAP authentication problem in the customer environment: The error message was received right after entering the password. Tshark says: 1 0.000000000 192.168.99.200 → 10.10.10.10 TCP 74 44780 → 3269 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 SACK_PERM=1 TSval=2891116193 TSecr=0 WS=128 2 0.001225814 10.10.10.10 → 192.168.99.200 TCP 74 3269 → 44780 [SYN, ACK] Seq=0 Ack=1 Win=8192 Len=0 MSS=1460 […]
How to Decrypt TLS Traffic with Wireshark
This is a small note to keep the links to posts by Peter Wu: Extract pre-master keys from an OpenSSL application Extracting openssl pre-master secret from apache2 Example in Debian Buster: With the keys saved by that process (and doing the packet capture at the same time, in either server or client side), you can […]