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 […]
Tag: linux
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 […]
NetBox Database Backup
A short memo how to backup any PostgreSQL database: In .pgpass (you should keep this file protected): netbox-db-backup.sh: That will also find and delete backup files older than MAXDAYS.
Get Linux Distribution Name and Version with Python
Since Debian 10 Buster there is no minor version number in lsb_release output or /etc/os-release anymore. Bug has been filed, but apparently there is no will to get the full version number back. The dist() and linux_distribution() functions in the platform module in Python have been deprecated in 3.5 and removed in 3.8.0: Also, the […]
Oneshot Service in Linux Systemd
My trusty old VDR box started behaving erratically: sometimes the IR remote didn’t do anything. Rebooting the whole box usually helped, but not always. Eventually I was able to narrow the problem down: for some reason the LIRC serial driver did not correctly detect the IR receiver in the serial port at the boot. I […]
Linux Routing Memos
These are just small hints and memos what to do on a Debian Linux setup. This is not a complete guide on doing a secured routing environment with Linux. /etc/sysctl.conf: net.ipv4.ip_forward=1 Configure /etc/network/interfaces iptables -t nat -A POSTROUTING -o <upstream_interface> -j MASQUERADE apt-get install iptables-persistent apt-get install iftop apt-get install conntrack conntrack -L -s 10.11.1.10 […]
NetBox Install on Debian 9
When installing NetBox on Debian 9 and Apache, the instructions in http://netbox.readthedocs.io/en/latest/ are fine, just some small additional operations are needed. The libapache2-mod-wsgi-py3 package needs to be installed as well, otherwise you will get errors about the “WSGIPassAuthorization on” command when starting Apache [this has later been addressed in commit b917e8d] Disable the “000-default” site […]