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Old 08-31-2011, 02:45 PM
Camaleón
 
Default How to reduce number of loaded kernel modules?

On Wed, 31 Aug 2011 15:39:41 +0200, Csanyi Pal wrote:

> I have a rather impressive list of loaded modules.

How many, how many? :-)

sm01@stt008:~$ lsmod| wc -l
67

> I'm not shure whether are they really needed?

Some modules are automatically loaded on demand or as a requirement for
another module.

> How can I know which modules I don't need so I can have those
> blacklisted?

Hard to tell... but if they are loaded there must be a good reason for
it :-?

Greetings,

--
Camaleón


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Old 08-31-2011, 02:53 PM
Darac Marjal
 
Default How to reduce number of loaded kernel modules?

On Wed, Aug 31, 2011 at 03:39:41PM +0200, Csanyi Pal wrote:
> Hi,
>
> I have a rather impressive list of loaded modules. I'm not shure whether
> are they really needed?
>
> How can I know which modules I don't need so I can have those
> blacklisted?

Generally speaking, the kernel only loads modules it needs. Typical
methods for this include udev discovering hardware (so the kernel loads
the driver for it) or modules or user-space software depending on other
modules (such as how the wireless system depends on some of the hashing
modules).

So, in a normal system, the modules are loaded because they are needed.
(The corollary to this is that when modules are not needed, such as
removing a device, they are unloaded).

Blacklisting is usually only needed if you have a broken modules or
there are two modules that service your needs and you need to use the
other one (for example, a USB device might be detected as needed
cdc-ether, but you know that actually it doesn't, so you blacklist
cdc-ether).

As Debian's stock kernel is designed for maximum flexibility, having a
couple of hundred modules loaded is not unexpected.

--
Darac Marjal
 
Old 09-01-2011, 11:29 AM
Camaleón
 
Default How to reduce number of loaded kernel modules?

On Thu, 01 Sep 2011 07:45:50 +0200, Csanyi Pal wrote:

> Camaleón <noelamac@gmail.com> writes:
>
>> On Wed, 31 Aug 2011 15:39:41 +0200, Csanyi Pal wrote:
>>
>>> I have a rather impressive list of loaded modules.
>>
>> How many, how many? :-)
>>
>> sm01@stt008:~$ lsmod| wc -l
> 155

That's too much.

On my netbook there are "just" 82 loaded (67 on the desktop).

By reading the kernel bug report you mentioned in your reply to Darac, I
see most of the modules are required for you iptables/netfiler/network
rules system so... just for debugging your problem you can just try to:

1/ Blacklist "pegasus" module if you think this is the one causing your
pain. Maybe is not...

2/ Or you can boot in "init 1" (single-user) with no network to avoid
related modules being loaded.

3/ Unload manually all of the non-crucial modules (sch*, ipt*, nf*,
xt*...).

Greetings,

--
Camaleón


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Old 09-01-2011, 03:02 PM
D G Teed
 
Default How to reduce number of loaded kernel modules?

On Thu, Sep 1, 2011 at 2:53 AM, Csanyi Pal <csanyipal@gmail.com> wrote:

Darac Marjal <mailinglist@darac.org.uk> writes:



> On Wed, Aug 31, 2011 at 03:39:41PM +0200, Csanyi Pal wrote:

>> I have a rather impressive list of loaded modules. I'm not shure whether

>> are they really needed?

>>

>> How can I know which modules I don't need so I can have those

>> blacklisted?

>

> Generally speaking, the kernel only loads modules it needs. Typical

> methods for this include udev discovering hardware (so the kernel loads

> the driver for it) or modules or user-space software depending on other

> modules (such as how the wireless system depends on some of the hashing

> modules).

>

> So, in a normal system, the modules are loaded because they are needed.

> (The corollary to this is that when modules are not needed, such as

> removing a device, they are unloaded).

>

> Blacklisting is usually only needed if you have a broken modules or

> there are two modules that service your needs and you need to use the

> other one (for example, a USB device might be detected as needed

> cdc-ether, but you know that actually it doesn't, so you blacklist

> cdc-ether).



I have an usb ethernet adapter that sometimes freezes my Debian SID

system. I have mailed this problem to the Bugzilla Kernel org here:

https://bugzilla.kernel.org/show_bug.cgi?id=40372



The developers advices me to reduce loaded modules.

How can I do that?
As I read it, they are trying to reduce the number of modules fordiagnostic purposes. *It isn't intended to fix the problem, but perhapsallow a kernel dump to appear so there are some real details to
bite into for this bug report.*
This Debian wiki page might help for disabling the auto loadof modules. *The update-initramfs step is important, as manymodules load from within initfs, before your root partition is
even mounted.
http://wiki.debian.org/KernelModuleBlacklisting
Spend some time getting to know what they are, as disabling some can
cause the system to not boot up, or not very well. *I suspect you havesome sort of firewall package which is loading a lot of extra*unnecessarymodules. *There is also a chance the bug is one specific to the specialized
iptables*features provided by extra modules and your USB ethernet adapter driver.Some iptables modules are marked experimental and should be avoided.Modules such as*nf_conntrack_amanda are not standard for basic rules set
up in iptables, so there is likely something bringing that along.
 

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