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Strange modprobe errors with module ip_tables of PAE kernel 2.6.18 on RHEL 5

Ralph Grothe
Honored Contributor

Strange modprobe errors with module ip_tables of PAE kernel 2.6.18 on RHEL 5

Hi,

kernel and OS release are as follows:

# uname -srvi
Linux 2.6.18-53.el5PAE #1 SMP Wed Oct 10 16:48:18 EDT 2007 i386

# cat /etc/redhat-release
Red Hat Enterprise Linux Server release 5.1 (Tikanga)

As can be seen the RHEL installer must have selected a kernel with Physical Address Extensions implemented because the physical memory of the box is 4 GB (I assume this to be the threshold criteria of the installer to select a PAE kernel?)
I don't beleive that the colleague who installed the OS on this box made this PAE choice deliberately.

# free -mo
total used free shared buffers cached
Mem: 4050 3971 78 0 137 3344
Swap: 2047 0 2047


I have no experience with PAE kernels from RedHat (or other distro),
because at home I don't have HW with that much memory, and on the other hand most of our other RHEL servers meanwhile use 64bit kernels.

What is annoying and kind of irritating are log entries in messages from failed modprobe invocations for loading of Netfilter modules such as these:


# grep modprobe /var/log/messages
Jul 4 08:49:12 somehost modprobe: WARNING: Error inserting x_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/netfilter/x_tables.ko): Operation not permitted
Jul 4 08:49:12 somehost modprobe: FATAL: Error inserting ip_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/ipv4/netfilter/ip_tables.ko): Operation not permitted
Jul 4 08:49:46 somehost modprobe: WARNING: Error inserting x_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/netfilter/x_tables.ko): Operation not permitted
Jul 4 08:49:46 somehost modprobe: FATAL: Error inserting ip_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/ipv4/netfilter/ip_tables.ko): Operation not permitted
Jul 4 08:50:09 somehost modprobe: WARNING: Error inserting x_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/netfilter/x_tables.ko): Operation not permitted
Jul 4 08:50:09 somehost modprobe: FATAL: Error inserting ip_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/ipv4/netfilter/ip_tables.ko): Operation not permitted
Jul 4 08:50:18 somehost modprobe: WARNING: Error inserting x_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/netfilter/x_tables.ko): Operation not permitted
Jul 4 08:50:18 somehost modprobe: FATAL: Error inserting ip_tables (/lib/modules/2.6.18-53.el5PAE/kernel/net/ipv4/netfilter/ip_tables.ko): Operation not permitted


We could well live with a kernel which hadn't enabled module support for Netfilter because on this host we make no use of Iptables at all,
and thus have deliberately disabled startup of iptables:

# echo ip{,6}tables|xargs -n1 chkconfig --list
iptables 0:off 1:off 2:off 3:off 4:off 5:off 6:off
ip6tables 0:off 1:off 2:off 3:off 4:off 5:off 6:off


Nevertheless, something must have loaded the iptables modules

# lsmod|grep tables
ip_tables 17029 1 iptable_filter
x_tables 17349 1 ip_tables


I have no idea which process is trying to load these unneeded modules and causing the above log entries in messages.

I would like to deactivate any load attempts of these modules, without having to compile a new kernel which has no Netfilter hooks in it anymore.
We would like to stick with the RedHat supplied kernel, maybe also to stay eligible to RH support or similar.

I could add some startup script that would unload any loaded Netfilter modules like this

# rmmod ip_tables
ERROR: Module ip_tables is in use by iptable_filter

# modprobe -r iptable_filter

# modprobe -r ip_tables

# lsmod|grep -c tables
0


But I would consider this pretty weird.

Any other proposals or maybe explanations of what's going on?

Rgds.
Ralph
Madness, thy name is system administration
2 REPLIES
skt_skt
Honored Contributor

Re: Strange modprobe errors with module ip_tables of PAE kernel 2.6.18 on RHEL 5

here is what i see in one my servers

#lsmod|grep tables
ip6_tables 50049 1 ip6table_filter
x_tables 50377 3 ip6t_REJECT,xt_tcpudp,ip6_tables

# service iptables status
Firewall is stopped.

what is the status of "service iptables status" now?
Ralph Grothe
Honored Contributor

Re: Strange modprobe errors with module ip_tables of PAE kernel 2.6.18 on RHEL 5

Hi Santosh,

exactly the same output, "Firewall is stopped".

Also the curious log entries haven't reappeared in /var/log/messages.
Madness, thy name is system administration