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On all the VPSs the iptables modules are not enabled by default , and usually client get below error in this case :

“iptables v1.2.8: can’t initialize iptables table `filter’: Table does not exist (do you need to insmod?)
Perhaps iptables or your kernel needs to be upgraded.”

The iptable modules can be enabled through shell or vzmc , through vzmc you can simply select the modules , press enable and the vps will get restarted and the iptables modules will be enabled. Before enabling iptables on VPS, it needs to make sure that the iptables modules are enabled on the Hardware Node. In order to enable iptables modules on Hardware Node, edit /etc/sysconfig/iptables-config file on a Virtuozzo hardware node and look for the following parameter value:

IPTABLES_MODULES=”ipt_REJECT ipt_tos ipt_TOS ipt_LOG ip_conntrack ipt_limit ipt_multiport iptable_filter iptable_mangle ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_length ipt_state iptable_nat ip_nat_ftp”

Also edit /etc/sysconfig/vz file on a hardware node and look for the following parameter value:

IPTABLES=”ipt_REJECT ipt_tos ipt_TOS ipt_LOG ip_conntrack ipt_limit ipt_multiport iptable_filter iptable_mangle ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_length ipt_state iptable_nat ip_nat_ftp”

Next step would be enabling iptables modules on VPS. This is how we can do it:

VEID=XXX (where XXX is the actual VPS ID that can be checked using “vzlist -a” command)

vzctl stop $VEID ; vzctl set $VEID –iptables ipt_REJECT –iptables ipt_tos –iptables ipt_TOS –iptables ipt_LOG –iptables ip_conntrack –iptables ipt_limit –iptables ipt_multiport –iptables iptable_filter –iptables iptable_mangle –iptables ipt_TCPMSS –iptables ipt_tcpmss –iptables ipt_ttl –iptables ipt_length   –iptables ipt_state –iptables iptable_nat –iptables ip_nat_ftp –save

vzctl set $VEID –numiptent 2000 –save

vzctl start $VEID

• Reboot the system and wait for the GRUB screen to appear.
• Highlight the kernel version you’re currently using (usually the newest version) from the GRUB list.
• Press “e” to be taken to the boot commands edit screen, highlight the line which starts with kernel and press “e” again.
• Add “single” to the end of the line, so it will look like this:

kernel /vmlinuz-kernel-version ro root=LABEL=/ rhgb quiet single

• Press “Enter” to save the changes
• Press “b” to boot in single user mode.

The system will begin loading and, at some point, you will be presented with a root bash prompt.

In the new prompt type “passwd” and choose a new password for root.When done, type reboot to restart the system. After reboot, GRUB will be back to normal so no further modifications are required.

NOTE: If you are asked for the root password before dropping you in a bash prompt in single user mode, you should follow the instructions above and append “single init=/bin/bash” to the kernel line, not just “single“.