why is a reboot needed before upgrading?

[Ranjan Maitra]

According to the first step here

https://docs.fedoraproject.org/en-US/quick-docs/upgrading-fedora-offline/

a reboot is needed before proceeding with the upgrade. Just curious why?

In the past, I did not reboot for days, but it did not matter and things went smoothly for the upgrade.

Many thanks and best wishes,
Ranjan

[Marco Moock]

Am 26.04.2025 um 09:51:03 Uhr schrieb Ranjan Maitra via users:
> a reboot is needed before proceeding with the upgrade. Just curious
> why?

If you are running an outdated kernel, you should reboot the current one
to be able to properly remove the old kernel during the upgrade.

[Ranjan Maitra]

On Sat Apr26'25 04:53:50PM, Marco Moock wrote:
> From: Marco Moock 
> Date: Sat, 26 Apr 2025 16:53:50 +0200
> To: [e-mail]
> Reply-To: Community support for Fedora users 
> Subject: Re: why is a reboot needed before upgrading?
>
> Am 26.04.2025 um 09:51:03 Uhr schrieb Ranjan Maitra via users:
> > a reboot is needed before proceeding with the upgrade. Just curious
> > why?
>
> If you are running an outdated kernel, you should reboot the current one
> to be able to properly remove the old kernel during the upgrade.

Thank you for your explanation. I am just trying to understand: why does it matter? I am currently running 6.13.9 but the latest installed is 6.14.3. Aren't either of these going to be ignored when the upgrade happens anyway?

Many thanks,
Ranjan
> -- 
> Gruß
> Marco
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[Marco Moock]

Am 26.04.2025 um 10:01:59 Uhr schrieb Ranjan Maitra via users:
> Thank you for your explanation. I am just trying to understand: why
> does it matter? I am currently running 6.13.9 but the latest
> installed is 6.14.3. Aren't either of these going to be ignored when
> the upgrade happens anyway?

Removing the kernel that is running at this time is a rather bad idea.
That is why a reboot is recommended when a kernel update has been
performed before the system upgrade.

[Ranjan Maitra]

On Sat Apr26'25 05:07:46PM, Marco Moock wrote:
> From: Marco Moock 
> Date: Sat, 26 Apr 2025 17:07:46 +0200
> To: [e-mail]
> Reply-To: Community support for Fedora users 
> Subject: Re: why is a reboot needed before upgrading?
>
> Am 26.04.2025 um 10:01:59 Uhr schrieb Ranjan Maitra via users:
> > Thank you for your explanation. I am just trying to understand: why
> > does it matter? I am currently running 6.13.9 but the latest
> > installed is 6.14.3. Aren't either of these going to be ignored when
> > the upgrade happens anyway?
>
> Removing the kernel that is running at this time is a rather bad idea.
> That is why a reboot is recommended when a kernel update has been
> performed before the system upgrade.

Does not the current kernel keep running until there is a reboot? Yes, I know it is recommended to reboot with a kernel update but my desktop and server run for months  before a reboot.

Anyway, it is still not clear to me why the reboot is needed before an upgrade as per the instructions. What happens if this is not done?

Ranjan
> -- 
> Gruß
> Marco
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[Doug H.]

On Sat, Apr 26, 2025, at 8:27 AM, Ranjan Maitra via users wrote:
> Anyway, it is still not clear to me why the reboot is needed before an 
> upgrade as per the instructions. What happens if this is not done?

It will continue to be the same basic answer no matter how many times you ask.

It is wise to be *running* on a fully updated system when you do your full version upgrade.

There might be bugs in the older stuff that could effect the upgrade. There might not be.

[Ranjan Maitra]

On Sat Apr26'25 08:31:31AM, Doug H. wrote:
> From: "Doug H." 
> Date: Sat, 26 Apr 2025 08:31:31 -0700
> To: Fedora Users 
> CC: Ranjan Maitra 
> Reply-To: Community support for Fedora users 
> Subject: Re: why is a reboot needed before upgrading?
>
> On Sat, Apr 26, 2025, at 8:27 AM, Ranjan Maitra via users wrote:
> > Anyway, it is still not clear to me why the reboot is needed before an 
> > upgrade as per the instructions. What happens if this is not done?
>
> It will continue to be the same basic answer no matter how many times you ask.

But the question was on why, not what which is also clear in the instructions.
> It is wise to be *running* on a fully updated system when you do your full version upgrade.
>
> There might be bugs in the older stuff that could effect the upgrade. There might not be.

Right, but does not the upgrade process keep both the currently running (older) kernel, the updated kernel (with the refresh command) and the one that gets installed as part of the upgrade? Then, the most recent updated kernel is available to the upgrade process, no?

Thanks,
Ranjan
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[Barry]

> On 26 Apr 2025, at 17:12, Ranjan Maitra via users  wrote:
>
> But the question was on why, not what which is also clear in the instructions.

It is not just the kernel that may have changed but also a reboot ensures all services are running up to date code.

By rebooting you place the system into a known healthy and tested state.

That gives you the lowest risk basis to do the upgrade.

Barry

[Marco Moock]

Am 26.04.2025 um 10:27:21 Uhr schrieb Ranjan Maitra via users:
> Does not the current kernel keep running until there is a reboot?

It does.
> Yes, I know it is recommended to reboot with a kernel update but my
> desktop and server run for months  before a reboot.

An upgrade needs a reboot anyway.

[Tim]

On Sat, 2025-04-26 at 17:33 +0200, Marco Moock wrote:
> An upgrade needs a reboot anyway.

This!!

Yes, I know we're reticent to go rebooting if we really do not need to.
But a system upgrade is a complete interruption to whatever you were
doing beforehand.  You may as well reboot before starting, it makes
sure that there is nothing unexpected still running in the background,
amongst other things.  You don't want to go through the palaver of
upgrading a system and have it bomb out before it finishes.

I know there's many a times I've logged out, hopped over to a command
line screen via CTRL ALT F2 to do something as root, then out of
curiosity have run "top" and seen that my user was apparently still
logged in and running various things.  And they still are many hours
later.

[Mike Wright]

On 4/27/25 01:07, Tim via users wrote:
> Yes, I know we're reticent to go rebooting if we really do not need to.

In early microsoft days (still?) reboot was a mantra.  For linux users 
uptime was a badge of honor and proudly displayed in mail footers.

[Tim]

Tim:
> > Yes, I know we're reticent to go rebooting if we really do not need to.

Mike Wright:
> In early microsoft days (still?) reboot was a mantra.  For linux users 
> uptime was a badge of honor and proudly displayed in mail footers.

[tim@rocky ~]$ uptime 
 15:35:38 up 51 days,  5:10, 13 users,  load average: 0.25, 0.21, 0.22

;-)

I have another Fedora box that is rarely shutdown or rebooted, but
suspended.  It's uptime calculation is quite misleading.  It's
certainly not been *running* for the amount of time it says.

[Roger Heflin]

The answer is that is they way it is suggested to be done and/or the
way that it was tested.

If you do not stand on one leg facing south under a full moon when
doing it then that is not a "supported" path.   Most software vendors
do it this way, and if anything goes wrong will blame that on some
trivial deviation from the "magical" process they tested and/or have
used before.

I do the unsupported dnf upgrade releasever=xx and I do that, and then
reboot once.   But I can solve 99% of dnf/rpm upgrade issues, and can
fix a failed boot.  I was also support of last resort for a company
with >20k running physicals and VMs so have pretty much seen just
about every sort of stupidity and/or issue at one time or another and
fixed the issue most of the time.

On Sat, Apr 26, 2025 at 10:02 AM Ranjan Maitra via users
 wrote:
> On Sat Apr26'25 04:53:50PM, Marco Moock wrote:
> > From: Marco Moock 
> > Date: Sat, 26 Apr 2025 16:53:50 +0200
> > To: [e-mail]
> > Reply-To: Community support for Fedora users 
> > Subject: Re: why is a reboot needed before upgrading?
> >
> > Am 26.04.2025 um 09:51:03 Uhr schrieb Ranjan Maitra via users:
> > > a reboot is needed before proceeding with the upgrade. Just curious
> > > why?
> >
> > If you are running an outdated kernel, you should reboot the current one
> > to be able to properly remove the old kernel during the upgrade.
>
> Thank you for your explanation. I am just trying to understand: why does it matter? I am currently running 6.13.9 but the latest installed is 6.14.3. Aren't either of these going to be ignored when the upgrade happens anyway?
>
> Many thanks,
> Ranjan
> > --
> > Gruß
> > Marco
> > Send unsolicited bulk mail to [e-mail]
> >
> > users mailing list -- [e-mail]
> > To unsubscribe send an email to [e-mail]
> > Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/
> > List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines
> > List Archives: https://lists.fedoraproject.org/archives/list/[e-mail]
> > Do not reply to spam, report it: https://pagure.io/fedora-infrastructure/new_issue
>
> --
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[Doug Herr]

On Sat, Apr 26, 2025, at 7:53 AM, Marco Moock wrote:
> If you are running an outdated kernel, you should reboot the current one
> to be able to properly remove the old kernel during the upgrade.

Just to clear this up...

I think this is not actually correct (maybe part of the issue Rajan was having).

The upgrade is done "offline", meaning that it is done early in a reboot. So...

1. Run for days or weeks.
2. Do a regular update which adds a new kernel.
3. Do your Fedora version update without bothering to reboot.
4. Last step of that upgrade (before it applies the packages) is a "special" reboot.

The reboot that is used to get to the "offline" state where it applies the packages will actually use that new kernel that you installed in step 2. So it should then be able to remove your oldest kernel during the process.

The trouble is that you had not rebooted to verify that that new kernel actually runs on your system. If it does not then you might have a failure during the upgrade reboot.

Bottom line is back to the simple "best practice" of getting to a fully updated and *reboot* tested state before you do a full version upgrade.

[Ranjan Maitra]

On Sat Apr26'25 10:05:22AM, Doug Herr wrote:
> From: Doug Herr 
> Date: Sat, 26 Apr 2025 10:05:22 -0700
> To: Fedora Users 
> Reply-To: Community support for Fedora users 
> Subject: Re: why is a reboot needed before upgrading?
>
> On Sat, Apr 26, 2025, at 7:53 AM, Marco Moock wrote:
> > If you are running an outdated kernel, you should reboot the current one
> > to be able to properly remove the old kernel during the upgrade.
>
> Just to clear this up...
>
> I think this is not actually correct (maybe part of the issue Ranjan was having).

Right, what you say below was my question.
> The upgrade is done "offline", meaning that it is done early in a reboot. So...
> Run for days or weeks.
> Do a regular update which adds a new kernel.
> Do your Fedora version update without bothering to reboot.
> Last step of that upgrade (before it applies the packages) is a "special" reboot.
>
> The reboot that is used to get to the "offline" state where it applies the packages will actually use that new kernel that you installed in step 2. So it should then be able to remove your oldest kernel during the process.
>
> The trouble is that you had not rebooted to verify that that new kernel actually runs on your system. If it does not then you might have a failure during the upgrade reboot.
> Bottom line is back to the simple "best practice" of getting to a fully updated and *reboot* tested state before you do a full version upgrade.

Thanks very much for this response and clarification! I decided to reboot before the upgrade just in case.

However, since I use an X-server (slim for login and openbox for WM), my upgrade resulted in a broken system (unable to get a login screen or a text console). So I went back to F41 for now in order to first investigate the problem.

Best wishes,
Ranjan
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[Michael Schwendt]

On Sat, 26 Apr 2025 09:51:03 -0500, Ranjan Maitra via users wrote:
> According to the first step here
>
> https://docs.fedoraproject.org/en-US/quick-docs/upgrading-fedora-offline/
>
> a reboot is needed before proceeding with the upgrade. Just curious
> why?

As it is an older feature, there are older articles that explain it.
Such as but not limited to this one:
https://fedoramagazine.org/offline-updates-and-fedora-35/

[Doug H.]

On Sat, Apr 26, 2025, at 7:51 AM, Ranjan Maitra via users wrote:
> According to the first step here
>
> https://docs.fedoraproject.org/en-US/quick-docs/upgrading-fedora-offline/
>
> a reboot is needed before proceeding with the upgrade. Just curious why?

Another reason is to verify that your system is rebootable *before* you do a major upgrade.

If you had been running for weeks on end and there had been a drive error that trashed some core file in the /boot directory then it would be wise to identify and fix that issue before you do anything else.

Sometimes people will do strange things to their system based on some random web page they read. Sometimes those people will not reboot the system after fiddling with it. Days or weeks later they reboot and are surprised that they have a problem.

All that is to say that "best practices" are there to help you.

The good news is that most of the time you will not have a problem, even if you don't bother with that reboot.

Heck, I don't always bother to refresh my backup before a Fedora version update. I would never recommend that habit since I know why it is a good idea to do that refresh.

[Ranjan Maitra]

On Sat Apr26'25 09:28:42AM, Doug H. wrote:
> From: "Doug H." 
> Date: Sat, 26 Apr 2025 09:28:42 -0700
> To: Fedora Users 
> Reply-To: Community support for Fedora users 
> Subject: Re: why is a reboot needed before upgrading?
>
> On Sat, Apr 26, 2025, at 7:51 AM, Ranjan Maitra via users wrote:
> > According to the first step here
> >
> > https://docs.fedoraproject.org/en-US/quick-docs/upgrading-fedora-offline/
> >
> > a reboot is needed before proceeding with the upgrade. Just curious why?
>
> Another reason is to verify that your system is rebootable *before* you do a major upgrade.
>
> If you had been running for weeks on end and there had been a drive error that trashed some core file in the /boot directory then it would be wise to identify and fix that issue before you do anything else.
>
> Sometimes people will do strange things to their system based on some random web page they read. Sometimes those people will not reboot the system after fiddling with it. Days or weeks later they reboot and are surprised that they have a problem.
>
> All that is to say that "best practices" are there to help you.
>
> The good news is that most of the time you will not have a problem, even if you don't bother with that reboot.
> Heck, I don't always bother to refresh my backup before a Fedora version update. I would never recommend that habit since I know why it is a good idea to do that refresh.

Thank you for this explanation! I do not use random webpages and my refreshes usually report "Nothing to update/do" because my system is updated by a cron job every night.

Best wishes,
Ranjan