---
title: "Fedora Networking & Kernel Troubleshooting"
domain: troubleshooting
category: networking
tags: [fedora, networking, kernel, grub, nmcli, troubleshooting]
status: published
created: 2026-04-02
updated: 2026-04-02
---

# Fedora Networking & Kernel Troubleshooting

Two common issues on the MajorsHouse Fedora fleet (majorlab, majorhome): network connectivity dropping after updates or reboots, and kernel upgrades that break things. These are the quick fixes and the deeper recovery paths.

## Networking Drops After Reboot or Update

### Quick Fix

If a Fedora box loses network connectivity after a reboot or `dnf upgrade`, NetworkManager may not have brought the connection back up automatically:

```bash
nmcli connection up "Wired connection 1"
```

This re-activates the default wired connection. If the connection name differs on your system:

```bash
# List all known connections
nmcli connection show

# Bring up by name
nmcli connection up "your-connection-name"
```

### Why This Happens

- NetworkManager may not auto-activate a connection if it was configured as manual or if the profile was reset during an upgrade.
- Kernel updates can temporarily break network drivers, especially on hardware with out-of-tree modules. The new kernel loads, the old driver doesn't match, and the NIC doesn't come up.
- On headless servers (like majorlab and majorhome), there's no desktop network applet to reconnect — it stays down until you fix it via console or IPMI.

### Make It Persistent

Ensure the connection auto-activates on boot:

```bash
# Check current autoconnect setting
nmcli connection show "Wired connection 1" | grep autoconnect

# Enable if not set
nmcli connection modify "Wired connection 1" connection.autoconnect yes
```

## Kernel Issues — Booting an Older Kernel

When a new kernel causes problems (network, storage, GPU, or boot failures), boot into the previous working kernel via GRUB.

### At the GRUB Menu

1. Reboot the machine.
2. Hold **Shift** (BIOS) or press **Esc** (UEFI) to show the GRUB menu.
3. Select **Advanced options** or an older kernel entry.
4. Boot into the working kernel.

### From the Command Line (Headless)

If you have console access but no GRUB menu:

```bash
# List installed kernels
sudo grubby --info=ALL | grep -E "^(index|kernel|title)"

# Set the previous kernel as default (by index)
sudo grubby --set-default-index=1

# Or set by kernel path
sudo grubby --set-default=/boot/vmlinuz-6.19.9-200.fc43.x86_64

# Reboot into it
sudo reboot
```

### Remove a Bad Kernel

Once you've confirmed the older kernel works:

```bash
# Remove the broken kernel
sudo dnf remove kernel-core-6.19.10-200.fc43.x86_64

# Verify GRUB updated
sudo grubby --default-kernel
```

### Prevent Auto-Updates From Reinstalling It

If the same kernel version keeps coming back and keeps breaking:

```bash
# Temporarily exclude it from updates
sudo dnf upgrade --exclude=kernel*

# Or pin in dnf.conf
echo "excludepkgs=kernel*" | sudo tee -a /etc/dnf/dnf.conf
```

Remove the exclusion once a fixed kernel version is released.

## Quick Diagnostic Commands

```bash
# Check current kernel
uname -r

# Check network status
nmcli general status
nmcli device status
ip addr show

# Check if NetworkManager is running
systemctl status NetworkManager

# Check recent kernel/network errors
journalctl -b -p err | grep -iE "kernel|network|eth|ens|nm"

# Check which kernels are installed
rpm -qa kernel-core | sort -V
```

## Gotchas & Notes

- **Always have console access** (IPMI, physical KVM, or Proxmox console) for headless servers before doing kernel updates. If the new kernel breaks networking, SSH won't save you.
- **Fedora keeps 3 kernels by default** (`installonly_limit=3` in `/etc/dnf/dnf.conf`). If you need more fallback options, increase this number before upgrading.
- **Test kernel updates on one server first.** Update majorlab, confirm it survives a reboot, then update majorhome.
- **`grubby` is Fedora's preferred tool** for managing GRUB entries. Avoid editing `grub.cfg` directly.

Reference: [Fedora — Working with the GRUB 2 Boot Loader](https://docs.fedoraproject.org/en-US/fedora/latest/system-administrators-guide/kernel-module-driver-configuration/Working_with_the_GRUB_2_Boot_Loader/)

## See Also

- [docker-caddy-selinux-post-reboot-recovery](docker-caddy-selinux-post-reboot-recovery.md)
- [managing-linux-services-systemd-ansible](../01-linux/process-management/managing-linux-services-systemd-ansible.md)