Kmorph tool aims for Linux kernel recovery without a reboot

The multikernel project has introduced Kmorph, an open-source tool designed to recover from Linux kernel panics or hangs without a full system reboot. The tool works by running a successor kernel alongside the predecessor kernel, giving the successor a small reserved share of hardware such as one CPU core and 128 MB of RAM. A background service inside the backup continuously checks the main system. If the main kernel misses five consecutive probes, the successor begins a takeover.

Image: Hardware Busters

Reports say this method allowed an Nginx web server to recover with approximately two seconds of downtime. According to developers, switching over requires about one second. During this process, the successor stops all other CPUs, resets PCI devices, and hot-adds the remaining RAM. The tool can also be used for rebootless kernel upgrades. Should the transition stall during the first ten seconds, the previous system remains active.

The tool depends on an operating system version that incorporates the multikernel capability, absent from standard releases. The tool supports x86-64 and arm64 architectures. The project notes that takeovers are one-shot, meaning the new kernel remains unprotected until it arms its own successor. Adopted devices lose AER and secondary bus reset, and some memory may be stranded in small slivers. Additionally, services in standby mode must not touch the network or write persistent state before the takeover occurs.