Updated: 28 September 2026 · Applies to: AlmaLinux 9, Rocky Linux 9, Ubuntu 24.04 and Debian 12
Installing the kernel module for R1Soft (Server Backup) with r1soft-cki fails with "Unable to find a valid source directory" when the kernel headers for the running kernel are missing.
Fix (root)
dnf install kernel-devel-$(uname -r) kernel-headers-$(uname -r) # or yum r1soft-cki
If the exact version is not available, update the kernel and reboot first, so the running kernel matches the installable headers.
