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I have Fedora 20 setup with default kernel configuration, where bridge feature is enabled as a module (CONFIG_BRIDGE=m), and the bridge module loads as the system starts. I don't understand who initiates it, since I have not found anything about bridge.ko in /etc/sysconfig/modules/*. However it ends up in the memory and every time I have to 'rmmod' it.

I would like to prohibit loading of the bridge.ko on the start up, yet I still want to manually load/unload bridge.ko whenever necessary.

I know it is possible to use the blacklist feature in /etc/modprobe.d/blacklist.conf, but can anybody point out who is loading bridge.ko in default setup of Fedora 20?

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If you look at the output of lsmod it'll typically tell you which modules are loaded due to being a dependency of some other module. For example, in the case of bridge, it looks like stp & llc required it.

$ lsmod | grep brid
bridge                116006  1 ebtable_broute
stp                    12868  1 bridge
llc                    13941  2 stp,bridge

NOTE: This is from my Fedora 20 system as well (laptop). You can use another tool, modinfo to find out information about the 2 modules:

$ modinfo stp
filename:       /lib/modules/3.16.3-200.fc20.x86_64/kernel/net/802/stp.ko
license:        GPL
depends:        llc
intree:         Y
vermagic:       3.16.3-200.fc20.x86_64 SMP mod_unload 
signer:         Fedora kernel signing key
sig_key:        55:46:C1:1D:28:CF:EC:0B:46:B1:C1:F1:93:0D:6B:F3:EC:63:B0:67
sig_hashalgo:   sha256

$ modinfo llc
filename:       /lib/modules/3.16.3-200.fc20.x86_64/kernel/net/llc/llc.ko
description:    LLC IEEE 802.2 core support
author:         Procom 1997, Jay Schullist 2001, Arnaldo C. Melo 2001-2003
license:        GPL
depends:        
intree:         Y
vermagic:       3.16.3-200.fc20.x86_64 SMP mod_unload 
signer:         Fedora kernel signing key
sig_key:        55:46:C1:1D:28:CF:EC:0B:46:B1:C1:F1:93:0D:6B:F3:EC:63:B0:67
sig_hashalgo:   sha256

That didn't shed much more light on the situation, so let's see what Google has to say about "linux llc". Here's the project page and a synopsis of what this module is all about.

excerpt - https://code.google.com/p/linux-llc/

linux-llc is a collection of programs that form the base set of the Linux-LLC networking stack's userspace components for the Linux operating system.

Logical Link Control (LLC) is a sublayer of the IEEE 802.2 LAN Protocol Suite. LLC is the top sub-layer in the data link layer and is the common access method to the different medium access technologies such as Tokenring, Ethernet and FDDI. LLC sockets provides a convenient and easy to use method for accessing LLC1 and LLC2 functions from userspace.

An LLC2 socket inherits all the functionality of an LLC1 socket. The LLC1 socket uses the LLC datalink connectionless mode (Unacknowledged data transfer) protocol. Verses an LLC2 socket uses the LLC datalink connection oriented mode plus datalink connectionless mode.

So based on this information, I'd say this is a pretty core module, that you'll have a hard time removing and/or going without, especially if you're using any of the listed networking technologies.

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