Need a explanation for modprobe command !

[HaoDr]

Hi all,

I have ever read a document directing me to setup a small firewall with IP chains, as follows:
---------------------------------------------------------
Add the following commands into /etc/rc.d/rc.local

echo 1 > /proc/sys/net/ipv4/ip_forward
/sbin/modprobe ipchains
/sbin/ipchains -P forward DENY
/sbin/ipchains -A forward -i eth0 -s 172.16.16.0/24 -j MASQ
....
---------------------------------------------------------

So I am wondering why I have to use command "/sbin/modprobe ipchains " ? What does it for ? I always think I have already installed Ipchains package, and of course, it will be loaded at startup process, is it right ? So I don't need use the above command, it seems to be useless, isn't it ?
Please tell me about this issue.

Thanks for your help.

Hao Dr

 

[ifincham]

Hi,

Modprobe is similar to 'insmod' except it does dependency checking. If you do 'insmod' it just inserts a module into memory - effectively as an extension to the kernel. Some modules, however, depend (require) other modules. So modprobe checks in modules.dep for dependecies and 'insmod's all the dependent modules plus the one specified on the command line itself. Where does the modules.dep info come from ? From running the depmod -ae command which works out the dependencies.

See 'man modprobe' and 'man depmod'

Regards