CentOS hibernation by systemctl

husarz · 09-01-2019, 08:11 AM

Hey, when do hibernation on CentOS 7.6.1810 with 3.10.0-957.27.2.el7.x86_64 kernel as:

Code:

# systemctl hibernate

then system successfully hibernates.

But how does kernel know where to write data from RAM when the kernel is stock CentOS and no parameter 'resume=' provided to kernel?

ondoho · 09-01-2019, 08:18 AM

Succesful hibernate does not mean succesful wake-up - does that work, too?

husarz · 09-01-2019, 08:30 AM

Quote:

Originally Posted by ondoho

Succesful hibernate does not mean succesful wake-up - does that work, too?

Yes it works - I had hibernated, completely turned off the power for some time and after turned it on again it resumed in desired state.

Firerat · 09-01-2019, 08:55 AM

not certain, I think it is in the initramdisk

I guess it looks at metadata in swap, just a guess.

husarz · 09-10-2019, 01:53 PM

Quote:

Originally Posted by Firerat

not certain, I think it is in the initramdisk

I guess it looks at metadata in swap, just a guess.

What metadata ?

Firerat · 09-10-2019, 02:01 PM

Quote:

Originally Posted by husarz

What metadata ?

when the initramdisk checks the /etc/fstab and finds the swap partition it sees that swap contains hibernation data that would fit well on system it is booting.
and so resumes it

But just a guess

Edit: I got confused with something else

all the bits of data that describe the drive

manufacture/model/serialNo., the partition IDs, the filesystem IDs, which controller they are connected to and so on

https://en.wikipedia.org/wiki/Metadata