[sarkar]

Facets of Linux RAS: Kexec and Kdump:-

1. There are two facets of Linux RAS; Kexec and kdump. Both are serviceability features introduced in the 2.6 kernel.

2. Kexec uses the image overlay philosophy of the UNIX exec() system call to spawn a new kernel over a running kernel without the overhead of boot firmware. This can save several seconds of reboot time because boot firmware spends cycles walking buses and recognizing devices.

3. The less the reboot latency, the less the system downtime; so, this was one of the main motivations for developing kexec. However, kexec's most popular user is kdump.

4. Capturing a dump after a kernel crash is inherently unreliable because kernel code that accesses the dump device might be in an unstable state. Kdump circumvents this problem by collecting the dump after booting into a healthy kernel via kexec.