Linux on unixworld

Automatically Start Podman Containers with Systemd on RHEL 10

Sat, 28 Jun 2025 00:00:00 +0000

Quadlet is a systemd generator that allows you to manage Podman containers, pods, and networks using systemd unit files. This is especially useful for running containers under systemd as user services in a rootless environment.

This tutorial walks you through setting up and using Quadlet with rootless Podman containers on RHEL 10, Fedora 40+, and Rocky/AlmaLinux.

Prerequisites

RHEL/AlmaLinux/RockyLinux 10+
Podman (Container Management)

Install Podman

On RHEL 10, install Podman:

Mounting QCOW2 Disk Images and Resetting the Root Password Without Booting the VM in Ubuntu/Debian

Sun, 01 Jun 2025 00:00:00 +0000

This guide explains how to mount a QCOW2 disk image on your host server and reset the root password without starting the virtual machine.

Step 1 – Install the nbd package

sudo apt install nbd-client qemu-utils

Step 2 – Load the NBD kernel module

sudo modprobe nbd

Step 3 – Connect the QCOW2 image as a network block device

sudo qemu-nbd --connect=/dev/nbd0 /PATH_TO_IMAGE/image.qcow2

Step 4 – Identify partitions in the QCOW2 image

From QNAP to TrueNAS

Sun, 25 May 2025 00:00:00 +0000

This is a short overview of how my QNAP server evolved into the system it is today. It received more memory, a new OS, an additional PCIe module, and more.

Getting Started

A few years ago, I decided to move out of the cloud and bring my data home. As an admin with limited experience at the time, I chose to play it safe and bought a QNAP TS-453B NAS. Here’s a quick hardware rundown:

Moving VM from xen to proxmox

Sun, 11 May 2025 00:00:00 +0000

Migration Workflow: XenServer to Proxmox

1. Prepare on XenServer (source node)

Turn off the VM and activate its LVM logical volume:

xe vm-disk-list vm=source.host.name

# get the logical volume ID
lvdisplay | grep LV_DISK_ID 

# Activate the logical volume
lvchange -a y /dev/VG_XenStorage-LV_DISK_ID/VHD-ID

Tip: Replace LV_DISK_ID and VHD-ID with actual values from lvdisplay.

2. Export over the network (Xen to Proxmox)

Start listener on destination (Proxmox):

nc -l -p 5000 | pv | dd bs=4096 of=/dev/mapper/vg-vm--111--disk--0

Then send the raw disk from source (XenServer):

Build your Proxmox templates with packer

Wed, 07 May 2025 00:00:00 +0000

In the world of virtualization and infrastructure as code (IaC), automating the creation of virtual machine templates is a critical time-saver. This article introduces my open-source project that uses HashiCorp Packer to create standardized VM templates in Proxmox Virtual Environment (PVE).

The Problem with Manual Templates

Creating VM templates manually in Proxmox is time-consuming and error-prone. Each time you need a new template, you must:

Download the ISO
Create a new VM
Install the operating system
Configure basic settings
Convert to template

This process becomes tedious when managing multiple distributions or versions, and it’s difficult to ensure consistency.

Rebooting a Linux with I/O Errors

Wed, 07 May 2025 00:00:00 +0000

When a Linux system encounters I/O errors and becomes unresponsive, rebooting it gracefully might not be possible. In such scenarios, you can use the SysRq mechanism to reboot the system forcibly. This tutorial explains how to reboot a Linux system with I/O errors using SysRq commands.

Steps to Reboot the System

1. Enable SysRq Commands

The SysRq mechanism must be enabled to allow low-level system commands. To enable it, run the following command as root or using sudo:

Rebuilding initramfs

Sun, 04 May 2025 00:00:00 +0000

Admins migrating VMs between different hypervisors often forget to rebuild the initramfs, which leads to missing drivers required by the target environment—causing the VM to fail to boot.

Here’s a quick summary of how to fix that:

We’ll use SystemRescue (sysrescue) instead of a CentOS installation CD for rebuilding initramfs—and in many cases, it’s even better because:

It’s lightweight and fast to boot
Includes all common tools: chroot, dracut, lvm2, mdadm, etc.
Actively maintained and not tied to a specific distro

Steps Using SystemRescue to Rebuild `initramfs`

Boot the VM with the SystemRescue ISO
Identify and mount your root filesystem

lvm vgchange -ay # Activate LVM volumes, if needed
lsblk # Identify root and boot partitions
mount /dev/mapper/centos-root /mnt
mount /dev/sda1 /mnt/boot # if /boot is separate

Chroot into your system

mount --bind /dev /mnt/dev
mount --bind /proc /mnt/proc
mount --bind /sys /mnt/sys
chroot /mnt

Rebuild initramfs with needed drivers

dracut -f -v
# Or specify kernel version:
dracut -f -v /boot/initramfs-$(uname -r).img $(uname -r)

Exit and reboot

exit
reboot

How to Configure Bridge on Bond With NetworkManager

Sat, 29 Mar 2025 00:00:00 +0000

Setting up a Linux bridge on a bonded interface improves network reliability and performance. Bonding combines multiple network interfaces into one for better speed and failover protection, while a Linux bridge acts like a virtual switch, connecting devices or virtual machines.

In this guide, you’ll learn how to create a Linux bridge over a bonded interface, ensuring a stable and efficient network setup. Let’s get started!

Network Diagram

eth0 ---|
 | --+-- bond0 --+-- br0
eth1 ---|

Create bridge

nmcli connection add type bridge \
 ifname br0 \
 ipv4.method manual \
 ipv4.addresses 192.168.0.40/24 \
 ipv4.gateway 192.168.0.1 \
 ipv4.dns "192.168.0.1" \
 ipv6.method ignore \
 ipv6.never-default true \
 bridge.stp no \
 con-name br0

I use a static IP address for my bridge. You will need to adjust the settings to match your needs.

How to install GNS3 on Fedora

Sat, 29 Mar 2025 00:00:00 +0000

What is GNS3 ?

Graphical Network Simulator-3 (shortened to GNS3) is a network software emulator first released in 2008. It allows the combination of virtual and real devices, used to simulate complex networks. It uses Dynamips emulation software to simulate Cisco IOS (WikiPedia).

How to install GNS3

I will show you how to install GNS3, dynamips, vpcs and ubridge on Fedora.

Enable RPMFusion repositories

Note: Non-free RPMFusion repository is required for dynamips. If you don’t need it, you can skip this step.

How to install node exporter on TrueNAS Scale

Sat, 29 Mar 2025 00:00:00 +0000

On TrueNAS Scale, Graphite is the only current supported option to export metrics, but in this tutorial we will setup node_exporter and prometheus to get metrics and setup alerts for our NAS. This will also allow us to use standard Node Exporter and ZFS dashboards in Grafana.

Download Node Exporter

Before proceeding, it’s recommended to store the Node Exporter and any configuration files on your storage pool. In this example, the storage pool is named tank, which is mounted under /mnt/tank. This ensures the files are stored persistently and are safe from potential system upgrades or reconfigurations.

Linux on unixworld

Automatically Start Podman Containers with Systemd on RHEL 10

Prerequisites

Install Podman

Mounting QCOW2 Disk Images and Resetting the Root Password Without Booting the VM in Ubuntu/Debian

From QNAP to TrueNAS

Getting Started

Moving VM from xen to proxmox

Migration Workflow: XenServer to Proxmox

1. Prepare on XenServer (source node)

2. Export over the network (Xen to Proxmox)

Build your Proxmox templates with packer

The Problem with Manual Templates

Rebooting a Linux with I/O Errors

Steps to Reboot the System

1. Enable SysRq Commands

Rebuilding initramfs

**Steps Using SystemRescue to Rebuild **initramfs

How to Configure Bridge on Bond With NetworkManager

Network Diagram

Create bridge

How to install GNS3 on Fedora

What is GNS3 ?

How to install GNS3

Enable RPMFusion repositories

How to install node exporter on TrueNAS Scale

Download Node Exporter

Steps Using SystemRescue to Rebuild `initramfs`