Generalizing an Image

Do not run these cleanup commands on a VM you plan to keep using as the same instance. They are intended for image preparation and should be run only on template VMs. Some of them, cloud-init cleanup and host key removal in particular, will affect network and SSH access to the VM.

Every VM cloned from a machine image inherits all of the source VM’s on-disk state. It is recommend that before you capture an image, SSH into the source VM and strip the bits that should be unique per VM, such as host keys, machine ID, cloud-init caches, logs, and shell history:

sudo cloud-init clean --logs --machine-id
sudo rm -f /etc/ssh/ssh_host_*
sudo rm -rf /var/log/* /tmp/* /var/tmp/*
sudo apt-get clean
sudo truncate -s 0 ~/.bash_history /root/.bash_history 2>/dev/null
history -c

Exit the SSH session when you are done, then stop the VM so its disk is in a consistent state for capture. The commands above assume a Debian or Ubuntu source VM. On other distributions, substitute the equivalent package-cache cleanup (for example, sudo dnf clean all on AlmaLinux).

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