Upgrade and reload kernel without rebooting in Slackware?

Geremia · 04-20-2019, 01:06 PM

Is it possible to upgrade and reload the Linux kernel without rebooting?

I'm running a webserver and cannot afford downtime.

glorsplitz · 04-20-2019, 03:45 PM

Maybe see here Livepatch: Linux kernel updates without rebooting?

Although slackware is not listed, it seems on my stable slackware there's this

Code:

zcat /proc/config.gz | grep LIVEPATCH
CONFIG_HAVE_LIVEPATCH=y
CONFIG_LIVEPATCH=y

What's yours say?

enorbet · 04-20-2019, 05:54 PM

Hello
I'm rather curious that, despite how interesting this facility is, since even mission critical computers have scheduled reboots and reboots only take just a few minutes and that almost all services must be interrupted for kernel replacement, what is it that you think you lose in a scheduled reboot?

upnort · 04-20-2019, 07:48 PM

Quote:

I'm running a webserver and cannot afford downtime.

Please explain why a web server can't be offline for the 90 seconds or so required for a reboot? If 100% uptime is required then perhaps invest in a HA cluster?

Lysander666 · 04-20-2019, 07:51 PM

Quote:

Originally Posted by upnort

Please explain why a web server can't be offline for the 90 seconds or so required for a reboot?

I swear some websites do it without even telling anyone.

glorsplitz · 04-20-2019, 08:25 PM

this sounds a little like "that which should not be named"™

Quote:

shorthand term that refers to a manner of responding to challenges that requires one to have the ability to think fast, to adapt, and to improvise when getting a job done

frankbell · 04-20-2019, 08:51 PM

Quote:

reboots only take just a few minutes

I have a friend who is a sysadmin for a moderate-sized hospital which uses Linux in a thin-client 24/7 environment. His server is a server class machine with oodles of RAM. Reboots are not a small matter in that environment.

It takes about 20 minutes for his server to reboot.

ehartman · 04-20-2019, 11:22 PM

Quote:

Originally Posted by glorsplitz

What's yours say?

According to the article you quoted you'll need a 4.x kernel at least, so Slackware 14.2 or -current (unless you build your own kernel, for older releases, of course).
That said: Pat doesn't supply the live patches you would need for this, so you would have to create them yourself; only complete new kernel builds or updated versions are being delivered for those Slackware releases (and not too many of them for 14.2 either).

chris.willing · 04-21-2019, 12:07 AM

Who cares why you want to do it - keep at it @Geremia and post results here for others who may be interested; others like me who don't mind pleading ignorance but would like to know - for whatever reason.

chris

upnort · 04-21-2019, 01:21 AM

Quote:

His server is a server class machine with oodles of RAM. It takes about 20 minutes for his server to reboot.

Disable memory checking in the BIOS.

I manage several Dell rack servers that host server containers and VMs. When I first started managing the servers the reboot times were long and stressful -- especially when remotely updating and rebooting. Curious, I rebooted locally and realized the delay was BIOS memory checks. Takes a long time with 72 GB of RAM. After disabling the memory checks, reboot times changed to about 3 to 3.5 minutes.

I'm curious if anybody can resolve the OP's request for not rebooting, but also curious why a "mere" web server can't be rebooted. Then again, perhaps the web site is a status page for ICBMs. Or George Carlin partial sports scores.

glorsplitz · 04-21-2019, 10:17 AM

this

Quote:

Who cares why you want to do it - keep at it @Geremia and post results here for others who may be interested

same here

Quote:

I'm curious if anybody can resolve the OP's request for not rebooting

digimaus · 04-21-2019, 02:46 PM

Quote:

Originally Posted by frankbell

I have a friend who is a sysadmin for a moderate-sized hospital which uses Linux in a thin-client 24/7 environment. His server is a server class machine with oodles of RAM. Reboots are not a small matter in that environment.

It takes about 20 minutes for his server to reboot.

I've worked in such an environment. My PowerEdge R710 takes about seven minutes to fully boot to Slackware 64 14.2. My HPE ProLiant takes about two minutes, tops.

My question is why, in that environment, that they wouldn't be running redundant servers? One goes down, the other one picks up within a minute or less.

I worked for a multinational farm/lawn equipment corporation that in this particular factory I worked at ran ESXI for eight virtual servers that ran the entire factory. We had two physical servers, both redundant, so if one went down, the other would get a signal and be online in less than one minute.

Relying on a single server, especially in a healthcare environment, seems like piss-poor practice. You have to reboot or shut down servers from time to time--replacing cooling fans is one thing that comes to mind--and prudent practice dictates that you plan for a backup server.

Makes me wonder what their business contingency plan looks like...

Just my unsolicited two cents' worth.

upnort · 04-21-2019, 04:00 PM

Quote:

My question is why, in that environment, that they wouldn't be running redundant servers? One goes down, the other one picks up within a minute or less.

Typically, money. Redundancy usually is satisfied with HA clusters, which require three systems. Gets expensive.

Quote:

We had two physical servers, both redundant, so if one went down, the other would get a signal and be online in less than one minute.

How did you keep both the host and guest systems synchronized between the two?

linus72 · 04-21-2019, 06:44 PM

Would kexec work here?
I know distros like NetBootCD use it....

https://wiki.archlinux.org/index.php/kexec

https://linux.die.net/man/8/kexec

https://slackbuilds.org/repository/1...m/kexec-tools/

Richard Cranium · 04-21-2019, 07:34 PM

That's why you have maintenance windows or HA environments. Honestly, pick one of the two methods and run with it.