KernelCare lets you patch the Linux kernel without rebooting, and this article walks through how to set it up on both Debian‑based and RHEL‑based distributions while also showing a quick way to wipe its cache. On Ubuntu or Debian you first download a signed installer script that adds an APT repository, then run the key command with your personal API key before enabling the kernelcare.service at boot so it automatically starts after each restart. For CentOS and RHEL, the same shell script configures YUM, followed by registering the key with kernelcare-apikey and starting the service; once running you can stop it, delete everything in /var/cache/kernelcare to reclaim space, and restart so fresh patches are fetched again. If connectivity fails or the daemon is unintentionally disabled after an upgrade, re‑enable it and check proxy settings, while a real‑world example showed that clearing the cache resolved a kernel module load failure after a power loss.

How to Install KernelCare and Clear Its Cache on Linux

KernelCare keeps your kernel patched without rebooting, but when you finally want to switch off the service or tidy up old patches, the cache can pile up. This article walks through installing KernelCare on both Debian‑based and RHEL‑based systems and shows a quick way to wipe its cache clean.

Installing KernelCare on Ubuntu/Debian

1. Get the signed installer

   wget -O kernelcare.deb https://kernelcare.com/kc-install.sh && bash kernelcare.deb

The script pulls a verified package and sets up the APT repository, so updates stay on track.

2. Add your API key – you get one from the KernelCare portal after signing in.

   sudo kc-apikey -s <YOUR_KEY>

The key ties the machine to your account; without it the service will refuse to run.

3. Enable and start the daemon

   sudo systemctl enable --now kernelcare.service

Enabling at boot means you never have to remember to turn it back on after a reboot.

4. Check status

   sudo kernelcarectl status

You should see “KernelCare service is running” and the current patch set.

Installing KernelCare on CentOS/RHEL

1. Install the RPM

   wget https://kernelcare.com/kc-install.sh && bash kc-install.sh

The script configures the YUM repository automatically.

2. Register your API key

   sudo kernelcare-apikey -s <YOUR_KEY>

3. Start the service

   sudo systemctl enable --now kernelcare

4. Verify

   sudo kernelcare status

Clearing KernelCare Cache

KernelCare keeps a copy of every patch it downloads in /var/cache/kernelcare. Over time that directory can grow to 200 MB or more, especially on long‑running servers.

1. Stop the daemon (you don't want new patches while cleaning).

   sudo systemctl stop kernelcare.service

2. Remove the cache folder

   sudo rm -rf /var/cache/kernelcare/*

This deletes all cached binaries, freeing space without touching your live kernel.

3. Restart the service to let it rebuild fresh patches if needed.

   sudo systemctl start kernelcare.service

When Things Go Wrong

• If kernelcarectl status shows “failed to connect to update server”, double‑check your network proxy settings; KernelCare needs a clear path to https://updates.kernelcare.com.
• A common mishap is leaving the daemon disabled after an upgrade. Run sudo systemctl enable kernelcare.service again if you notice the service isn't active.

Real‑World Observation

I once had a production server where KernelCare was silently applying patches until a sudden power loss left the machine in an inconsistent state. The next boot revealed “kernel module load failed”. Restarting the daemon and clearing /var/cache/kernelcare resolved the issue fast, proving that a clean cache can be lifesaving.

That’s it—KernelCare is installed and your cache is gone. Keep those kernels patched and the disk tidy!