Blog About Debian Linux Administration and Automation on Blunix GmbH

Ultimate Guide About Linux Server Security Basics for Debian

Tue, 04 Jun 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This extensive tutorial thoroughly explains the necessary security measures to secure a fresh Debian Linux server installation. It contains and explains all steps required to keep your server safe when it is publicly reachable over the internet.

It is written for those who “just want to host wordpress” or similar tools on Debian servers. It covers the essential security measures, provides insights on additional steps you can take and explains why basic security is usually sufficient for most hosting requirements.

Copying Files in Qubes OS: From and to dom0 and between VMs

Sat, 25 May 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

Qubes OS VMs are isolated from one another by design. Hence, copying files between VMs is made a bit more complicated by design. This tutorial explains how to copy files or directories from dom0 to a Qubes VM, from one Qubes VM to another VM, how to copy from a VM to dom0 and how to do all that automatically in BASH scripts.

How to Install OpenBSD on ARM based Hetzner Cloud Servers

Thu, 23 May 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

Installing OpenBSD on a Hetzner cloud server is very easy and only takes about five minutes. Here is everything you need to know in easy to follow steps.

Choosing the Correct Hetzner Cloud Server

Create a hetzner cloud server and make sure you choose the ARM variant:

How to Create Qubes OS VMs Using the Command Line

Tue, 21 May 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This tutorial explains how to create Qubes OS VMs on the command line using the Qubes management tools qvm-create , qvm-clone , qvm-prefs , qubes-prefs , qvm-run and qvm-volume .

It explains in detail how to create the different classes of Qubes OS VMs, namely TemplateVMs, AppVMs, DispVMs and StandaloneVMs, how to customize TemplateVMs by installing and configuring software, how root and private disks are used and cloned for each type of VM and how different Qubes Prefs can be used to modify the Qubes internal usage and behavior of VMs.

How to Configure a Hetzner Domains DNS Records for Cloudflare

Tue, 07 May 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

When setting the Nameserver records to cloudflare, this is not done using the regular DNS WebUI of hetzner. Instead, you have to do this directly where all the domains that are hosted with Hetzner are listed.

You can find the required settings at https://robot.hetzner.com/domain and NOT at dns.hetzner.com

Select your domain and change the Nameserver settings there:

Disposable Temporary Email Adresses with OpenSMTPD on Linux

Mon, 06 May 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blogpost describes in very simple and easy to follow steps how to setup an ultra-cheap self-hosted solution for temporary email addresses. You can use these email addresses, for example, to sign up for various services, like facebook, instagram, reddit, protonmail and others.

This approach guarantees that the email addresses you use to signup are not blacklisted and reject your account creation, which is often the case with most public temp mail providers. It is a self-hosted alternative to larger services like temp-mail.org , which are constantly blacklisted.

Increasing SSD Performance on Linux using Fstrim

Thu, 25 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

What does the Linux `fstrim` Command do?

fstrim is a command in Linux used to inform the filesystem to discard unused blocks on a solid-state drive (SSD), Non-Volatile Memory Drive (NVME) or thinly-provisioned storage device.

Howto use IPv6 on Hetzner Cloud Servers to Host a Website

Wed, 24 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

Introduction

Before starting with IPv6 you should check if your Internet Service Provider (ISP) supports IPv6. You can do so by simply accessing ipv6.google.com . This is the google search page, but via IPv6 instead of IPv4. If this works for you, you can continue reading the article. If it does not, complain to your ISP to setup IPv6 or start using a VPN like mullvad.net , which will allow you to access IPv6.

DNS Record Management in Git Repositories with luadns.com

Wed, 24 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blog post is not sponsored by LuaDNS. We are simply enthusiasts of their service and wish to extend the same level of convenience to others grappling with the management of copious DNS records.

Encryption Plausible Deniability on Linux with Cryptsetup LUKS

Tue, 23 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blog post provides a clear and straightforward guide on how to encrypt various storage devices - including USB sticks, external hard drives, and internal storage - for plausible encryption deniability on Linux. It focuses on using the cryptsetup tool with LUKS encryption, which is installed by default on most common Linux distributions like Ubuntu. The article details how to configure a detached LUKS header, effectively making it impossible for adversaries to prove the existence of encrypted data.

The Ultimate Tutorial About Linux Systemd Timers Job Scheduling

Sat, 20 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blog post describes how to create, manage and fully understand systemd timers, which are a replacement for classic Cron jobs . Systemd timers allow for a much more fine grained configuration of when or upon which events to execute jobs, scripts, commands or systemd services in various Linux distributions.

This article is written for Linux beginners and advanced users. It aims to be easy to understand. While the manual page man systemd.timer can be confusing at times, this tutorial contains extensive practical examples and explains all aspects and configuration options of systemd timers in great detail.

Step-by-Step Guide to Creating your First Flutter App

Sat, 06 Apr 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

Embarking on the journey to build your first Flutter app can be an exciting yet daunting task. Flutter, with its multiplatform support, fast development times, and the hot reload feature, stands out as a powerful toolkit for app development. However, the initial learning curve can seem steep for beginners. This guide aims to simplify the process, guiding you through crafting a unit converter app.

Gitlab upgrade signature invalid EXPKEYSIG 3F01618A51312F3F

Wed, 27 Mar 2024 00:00:00 +0000

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The Problem: Expired apt-key Signature Problem while Upgrading Gitlab

We encountered the following error message while upgrading our Gitlab server git.blunix.com:

Open Source Centralized Logging Server for Linux

Sun, 24 Mar 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blogpost describes how to install and configure systemd-journal-remote to stream logs of up to hundrets of client servers to a central log aggregation machine. It was designed to be easy to follow for Linux administrators with little Linux experience. All commands and configuration files required to setup this service are explained in detail and can be copy-pasted. It was written for and tested with Debian 13 and Ubuntu 24.04, but should work with any other Linux Distribution that is using systemd.

SMTP Email Relay for Debian Linux Servers with OpenSMTPD

Fri, 08 Mar 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This tutorial describes how to setup a secure SMTP Mail Relay on Debian or Ubuntu Servers with OpenSMTPD instead of Postfix for relaying Emails from (Web) applications to Email providers like Google Workspace or Gmail , Microsoft Outlook or Office 365 , ZOHO Mail , Amazon Workmail (AWS) and others.

The commands in this blogpost are tested with Debian 12 and Ubuntu 22.04 and should work with all other Debian based distributions and all other Linux distributions that provide a opensmtpd package. All configuration files are explained in detail. You are provided copy-pastable examples, all you need to adjust are your sending email addresses and SMTP credentials.

Ultimate guide to a performant and secure Nextcloud Server

Sun, 25 Feb 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This blogpost is designed to show in copy-pastable commands how to setup, manage and maintain a Nextcloud installation on a Hetzner dedicated or cloud server running Ubuntu 22.04 LTS. This Blog post is written for readers with little technical Linux knowledge, allowing you to setup of a secure and performant Nextcloud installation on your own inexpensive server easy and fast.

Automatically mirror Gitlab repositories to Github

Fri, 16 Feb 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

The Problem with mirroring from Gitlab to Github

We want to mirror some of our public Gitlab repositories to github for better visibility. There is a gitlab function available for that at Settings -> Repository -> Repository mirroring, which is documented here , but sadly it gives this error when used with github:

Howto setup borgbackup2 on Debian12 on Hetzner Cloud Servers

Mon, 12 Feb 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

1. Creating the Cloud Servers on Hetzner

This blogpost describes how to setup borgbackup2 on Debian Linux 12 with the German IaaS provider hetzner.com/cloud/ . It is designed to setup a working borgbackup system on up to around 50-100 servers depending on your workstations internet connection.

Howto Setup armbian on Orange PI 5 Plus with SPI and i2c Interfaces

Thu, 01 Feb 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

IMPORTANT SECURITY NOTICE! The website orangepi.org does not provide httpS. This means that all traffic from your computer to this website is not encrypted and can potentially be manipulated by a man in the middle attack . This blogpost contains multiple links to this website.

Introduction

The Orange PI 5 Plus is a faster and stronger competitor to the Raspberry PI 5 - it has more ressources and ports with up to 32 GB RAM, an the octa core ARM CPU Rockchip RK3588, up to 256 GB eMMC storage and two 2.5G ethernet ports it overpowers the Raspberry Pi 5s performance with ease. The downside in comparison to the Raspberry Pi 5 is that it has much less public content, from forum questions and answers to blog posts, online chat rooms and github libraries and tools. It is hence a bit for advanced users. The operating system provided by the company Orange Pi , which to our pleasure can be downloaded with httpS, is based on arch Linux and we did not investigate it further. For a Debian Linux based solution we chose armbian .

Interesting and common SSH commands, tips, tricks and hacks

Wed, 24 Jan 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

Access a private network servers port by jumphosting via publicly reachable server: ssh -L

The argument -L for the ssh command allows for forwarding remote ports to the local workstation.

Howto fix the Gitlab upgrade Error PG::DuplicateColumn: ERROR: column "encrypted_token" of relation "chat_names" already exists

Mon, 22 Jan 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

While upgrading from the apt installed omnibus gitlab Version 16.6.4-ce.0 on Debian 12, I encountered the following error message:

PG::DuplicateColumn: ERROR:  column "encrypted_token" of relation "chat_names" already exists

Note that even though the apt upgrade failed, apt is displaying the target version to be installed already:

apt-cache policy gitlab-ce|head
gitlab-ce:
  Installed: 16.7.2-ce.0
  Candidate: 16.7.2-ce.0
  Version table:
 *** 16.7.2-ce.0 500
        500 https://packages.gitlab.com/gitlab/gitlab-ce/debian buster/main amd64 Packages
        100 /var/lib/dpkg/status
     16.7.0-ce.0 500
        500 https://packages.gitlab.com/gitlab/gitlab-ce/debian buster/main amd64 Packages
[...]

The following postgresql will adjust the column name as required:

Howto fix Gitlab Upgrade Error: PG::UndefinedObject: ERROR: constraint "fk_262d4c2d19" for table "ci_pipelines" does not exist

Mon, 22 Jan 2024 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

While upgrading from the apt installed omnibus gitlab Version 16.6.0-ce.0 on Debian 12, I encountered the following error message:

PG::UndefinedObject: ERROR:  constraint "fk_262d4c2d19" for table "ci_pipelines" does not exist

The following SQL query displays all present postgresql constraints:

root@gitlab.server ~ # gitlab-psql
gitlabhq_production=# SELECT con.*
       FROM pg_catalog.pg_constraint con
            INNER JOIN pg_catalog.pg_class rel
                       ON rel.oid = con.conrelid
            INNER JOIN pg_catalog.pg_namespace nsp
                       ON nsp.oid = connamespace
       WHERE nsp.nspname = 'public'
             AND rel.relname = 'ci_pipelines';


  oid  |      conname      | connamespace | contype | condeferrable | condeferred | convalidated | conrelid | contypid | conindid | conparentid | confrelid | confupdtype | confdeltype | confmatchtype | conislocal | coninhcount | connoinheirt | conkey | confkey | conpfeqop | conppeqop | conffeqop | conexclop | conbin
-------+-------------------+--------------+---------+---------------+-------------+--------------+----------+----------+----------+-------------+-----------+-------------+-------------+---------------+------------+-------------+-----------
---+--------+---------+-----------+-----------+-----------+-----------+--------
 80430 | fk_190998ef09     |         2200 | f       | f             | f           | t            |    66450 |        0 |    75938 |           0 |     67466 | a           | n           | s             | t          |           0 | t           | {27}   | {1}     | {410}     | {410}     | {410}     |           |

 75711 | ci_pipelines_pkey |         2200 | p       | f             | f           | t            |    66450 |        0 |    75710 |           0 |         0 |             |             |               | t          |           0 | t           | {1}    |         |           |           |           |           |

 80714 | fk_3d34ab2e06     |         2200 | f       | f             | f           | t            |    66450 |        0 |    75704 |           0 |     66430 | a           | n           | s             | t          |           0 | t            | {18}   | {1}     | {96}      | {96}      | {96}      |           |

 80977 | fk_67e4288f3a     |         2200 | f       | f             | f           | t            |    66450 |        0 |    75710 |           0 |     66450 | a           | n           | s             | t          |           0 | t            | {32}   | {1}     | {15}      | {96}      | {410}     |           |

 81675 | fk_c262d728d4     |         2200 | f       | f             | f           | t            |    66450 |        0 |    75710 |           0 |     66450 | a           | n           | s             | t          |           0 | t            | {17}   | {1}     | {96}      | {96}      | {96}      |           |

 81870 | fk_d80e161c54     |         2200 | f       | f             | f           | t            |    66450 |        0 |    75718 |           0 |     66491 | a           | n           | s             | t          |           0 | t           | {28}   | {1}     | {410}     | {410}     | {410}     |           |

(6 rows)

This Github issue for gitlab hints to the solution:

Blog Post About How To use German Umlauts on US Layout Keyboards

Wed, 29 Mar 2023 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This post was revived for nostalgy and SEO purposes. It is still up to date though and works on most modern Debian based Linux distributions. The original version can be found on archive.org .

Creating a ~/.Xmodmap file

In order to map key combinations to specific special characters you have to create a .Xmodmap file within your users home directory. First we have to find out what the keycodes of the keys you want to map are. For this enter “xev” and press the appropriate key. You will get an output like this:

Howto use the Hetzner Backup Space with rsync

Wed, 26 Nov 2014 00:00:00 +0000

Please contact us if anything is not clearly described, does not work, seems incorrect or if you require support.

This post was revived for nostalgy and SEO purposes. It might be outdated. The original version can be found on archive.org .

1. The Problem

The www.hetzner.de Backup Space does not allow for rsync to change the linux uids. It however is often desirable to keep those file informations when doing backups. Rsync will print the following error when trying to copy files to the hetzner backup space mounted when via sshfs:

Blogposts from Blunix early days (2012-2014) on archive.org

Sun, 01 Jan 2012 00:00:00 +0000

Blog About Debian Linux Administration and Automation on Blunix GmbH

Ultimate Guide About Linux Server Security Basics for Debian

Copying Files in Qubes OS: From and to dom0 and between VMs

How to Install OpenBSD on ARM based Hetzner Cloud Servers

Table of contents

How to Create Qubes OS VMs Using the Command Line

How to Configure a Hetzner Domains DNS Records for Cloudflare

Disposable Temporary Email Adresses with OpenSMTPD on Linux

Increasing SSD Performance on Linux using Fstrim

Table of contents

Howto use IPv6 on Hetzner Cloud Servers to Host a Website

Table of contents

DNS Record Management in Git Repositories with luadns.com

Table of contents

Encryption Plausible Deniability on Linux with Cryptsetup LUKS

The Ultimate Tutorial About Linux Systemd Timers Job Scheduling

Step-by-Step Guide to Creating your First Flutter App

Table of contents

Gitlab upgrade signature invalid EXPKEYSIG 3F01618A51312F3F

Table of contents

Open Source Centralized Logging Server for Linux

SMTP Email Relay for Debian Linux Servers with OpenSMTPD

Ultimate guide to a performant and secure Nextcloud Server

Automatically mirror Gitlab repositories to Github

Table of contents

Howto setup borgbackup2 on Debian12 on Hetzner Cloud Servers

Table of contents

Howto Setup armbian on Orange PI 5 Plus with SPI and i2c Interfaces

Interesting and common SSH commands, tips, tricks and hacks

Table of contents

Howto fix the Gitlab upgrade Error PG::DuplicateColumn: ERROR: column "encrypted_token" of relation "chat_names" already exists

Howto fix Gitlab Upgrade Error: PG::UndefinedObject: ERROR: constraint "fk_262d4c2d19" for table "ci_pipelines" does not exist

Blog Post About How To use German Umlauts on US Layout Keyboards

Table of contents

Howto use the Hetzner Backup Space with rsync

Table of contents

Blogposts from Blunix early days (2012-2014) on archive.org