Reboot Without Rebooting: Updating Linux Userspace at the Speed of a Service Restart
summary
Soft‑reboot replaces the entire userspace by execv replacing PID 1 and pivoting to a new rootfs while the kernel and hardware stay untouched, implemented in systemd and available since systemd 254 (Ubuntu 24.04 ships 255). It preserves many sockets and FDs, uses lazy unmount so services can opt out of restart, and skips firmware, bootloader and device reprobe. Demo edits /etc/os-release, runs systemctl soft-reboot, and returns in seconds with kernel and uptime unchanged.
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chapters (11)
- 0:00Soft reboot in systemd
- 1:03Normal vs user space reboot
- 2:27Preserving kernel state
- 4:15Soft reboot advantages
- 6:24systemd init after reboot
- 8:32Kernel soft reboot
- 11:24kexec for user space
- 13:53File descriptors & sockets
- 14:56Critical services preserved
- 16:26Live soft reboot demo
- 20:30Q&A
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