5:48 p.m.
Hi,
Currently, values set in /etc/sysctl.conf are set on boot when sysctl
-p -e is called. This happens in /etc/network. Of course, setting
values for kernel modules not loaded at that point has no effect.
This caught me out recently, as I tried to set a value for one of the
conntrack modules. Because the relevant module wasn't loaded until
shorewall started on my system, and because shorewall is started after
the network, the setting didn't do anything. The way I fixed it is by
adding sysctl -e -p to rc.local, so that it is ran after all the other
init scripts. However, I could see that this approach might be unwise
since the nfs script uses sysctl to change some values, and
potentially that could be undone by bad settings in sysctl.conf.
My question then is: should there not be a service that runs sysctl on
boot, as the last thing before rc.local? I have seen this on other
distributions. This would make the following statement true: If you
want to make a change to /proc/sys persistent across reboots, then add
it to /etc/sysctl.conf. It currently isn't always true due to the
timing of systl being run, but that statement is, for many, expected
behaviour.
Thoughts?
Jonathan.
6:05 p.m.
On Sat, Sep 29, 2007 at 11:48:25PM +0100, Jonathan Underwood wrote:
Currently, values set in /etc/sysctl.conf are set on boot when
sysctl
-p -e is called. This happens in /etc/network. Of course, setting
values for kernel modules not loaded at that point has no effect.
FWIW: It is also called in an earlier stage, in rc.sysinit.
Of course, this doesn't solve your complaint...
--
-- Jos Vos <jos(a)xos.nl>
-- X/OS Experts in Open Systems BV | Phone: +31 20 6938364
-- Amsterdam, The Netherlands | Fax: +31 20 6948204
5:26 p.m.
On 01/10/2007, Bill Nottingham <notting(a)redhat.com> wrote:
Jonathan Underwood (jonathan.underwood(a)gmail.com) said:
> Thoughts?
As modules could be loaded at any time, it would seem the most
correct way would be to do it via a modprobe.d or udev rule.
I see your point. But, taken to it's logical conclusion, we'd scrap sysctl.conf
completely.
Actually, that would be the right thing to do - it's currently a badly defined
ad hock kludge.
I presume this issue will be shaken out during the initscripts reworking and
NetworkManager revisions in any case.
J.
(In stereo :)
7:25 p.m.
On Mon, Oct 01, 2007 at 11:26:54PM +0100, Jonathan Underwood wrote:
On 01/10/2007, Bill Nottingham <notting(a)redhat.com> wrote:
> Jonathan Underwood (jonathan.underwood(a)gmail.com) said:
> > Thoughts?
>
> As modules could be loaded at any time, it would seem the most
> correct way would be to do it via a modprobe.d or udev rule.
>
I see your point. But, taken to it's logical conclusion, we'd scrap sysctl.conf
completely.
Actually, that would be the right thing to do - it's currently a badly defined
ad hock kludge.
How many modules export sysctls instead of module parameters?
--
Matt Domsch
Linux Technology Strategist, Dell Office of the CTO
linux.dell.com & www.dell.com/linux
7:58 p.m.
Matt Domsch wrote:
How many modules export sysctls instead of module parameters?
Those are not really exported in a special way for sysctl. They are
simply proc nodes (files) under /proc/sys, and a *lot* of modules put
stuff in there for runtime configuration. I have 615 files in there on
this laptop.
/Thomas
4:27 a.m.
On 02/10/2007, Thomas M Steenholdt <tmus(a)tmus.dk> wrote:
Matt Domsch wrote:
>
> How many modules export sysctls instead of module parameters?
>
Those are not really exported in a special way for sysctl. They are
simply proc nodes (files) under /proc/sys, and a *lot* of modules put
stuff in there for runtime configuration. I have 615 files in there on
this laptop.
I could be wrong, but I don't think anything exports a seetting that
is only changeable with sysctl that is not also changeable by echo'ing
to a file under /proc/sys - sysctl seems rather obsolete in this
respect.
4:33 a.m.
Hi.
On Tue, 2 Oct 2007 10:27:10 +0100, Jonathan Underwood wrote:
I could be wrong, but I don't think anything exports a seetting
that
is only changeable with sysctl that is not also changeable by echo'ing
to a file under /proc/sys - sysctl seems rather obsolete in this
respect.
Personally, I prefer sysctl for that. Works better with sudo.
5:31 a.m.
Ralf Ertzinger wrote:
Hi.
On Tue, 2 Oct 2007 10:27:10 +0100, Jonathan Underwood wrote:
> I could be wrong, but I don't think anything exports a seetting that
> is only changeable with sysctl that is not also changeable by echo'ing
> to a file under /proc/sys - sysctl seems rather obsolete in this
> respect.
Personally, I prefer sysctl for that. Works better with sudo.
I agree that sysctl (or a similar tool - i'm not religious in this area)
is probably wanted, albeit not required on a system. Like I stated
somewhere else, sysctl "only" modifies things in /proc/sys that you
could easili do with something else. There is nothing that you can do
with sysctl that you can't do with echo, cat and find. Apart from having
a simple way to set a lot of different values in one go.
/Thomas
/Thomas
7:43 p.m.
Jonathan Underwood wrote:
On 01/10/2007, Bill Nottingham <notting(a)redhat.com> wrote:
> Jonathan Underwood (jonathan.underwood(a)gmail.com) said:
>> Thoughts?
> As modules could be loaded at any time, it would seem the most
> correct way would be to do it via a modprobe.d or udev rule.
>
I see your point. But, taken to it's logical conclusion, we'd scrap sysctl.conf
completely.
Actually, that would be the right thing to do - it's currently a badly defined
ad hock kludge.
I presume this issue will be shaken out during the initscripts reworking and
NetworkManager revisions in any case.
As discussed in the bug
https://bugzilla.redhat.com/show_bug.cgi?id=312481 , we might be able to
solve this in a good way, with a few updated tools. I'll outline the
thoughts here and let everybody join the discussion...
What Jonathan and I discussed, was the possibility of having the module
loading mechanism (modprobe) figure out what proc nodes a newly loaded
module provides and selectively, apply settings to those nodes only.
That would make it possible to have a single, system-wide sysctl.conf
file with settings for all sorts of modules, and we would no longer need
to worry, that perhaps our modules isn't loaded when the settings are
applied etc. Also, it makes sure that manually applied settings are not
touched.
See the following sniplet from the bugzilla discussion for an example:
-- snip --
My system is configured with net.ipv4.ip_forward = 0... But I'm plying
with routing so I did an echo -n 1 >/proc/sys/net/ipv4/ip_forward to
enable forwarding. Now I plug in my USB disk and modules gets loaded.
It's really important that ip_forward is still "1" at this point
-- snap --
This should work for boot, randomly loading and unloading modules,
manually changing /proc/sys settings at runtime etc.
Perhaps the heuristic needs to be: when loading a module, modprobe
should (using sysctl or otherwise) look at sysctl.conf and set any
values for entries created by the loading of this module, and disregard
all others. sysctl -p would then serve the purpose of resetting all
values to those in sysctl.conf, if needed by the user.
/Thomas (with random exempts from the BZ dialog with Jonathan Underwood)
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participants (6)
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Matt Domsch -
Ralf Ertzinger -
Thomas M Steenholdt