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Kalib Zen
Asked: 2020-05-14 07:54:24 +0800 CST

Cannot access into my server after running iptables-restore. How to revert this command

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I decided to run this command 

iptables-save | tee iptables_backup.conf | grep -v '\-A'

but instead I accidentally put an extra command iptables-restore and ran this and now my server is locked. I cannot SSH anymore:

iptables-save | tee iptables_backup.conf | grep -v '\-A' | iptables-restore

I can access my server from the rescue disk and view all the files, but how do I revert the above command to start my server ?

I'm using Centos 8.

iptables centos8

2 Answers

  1. Smart of you to take a backup. Why not use it?

    iptables-restore < iptables_backup.conf
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  2. Best Answer

    Since the backup was useless because it didn't contain ipv6, I should had done another backup for ipv6 like this:

    ip6tables-save

    I solved it by restoring the iptables to the original state at boot time using rc.local. So, when booting into recovery I edited this file:

    nano /etc/rc.d/rc.local

# Temporary commands to run once at startup to reset iptables to original state
iptables -F
iptables -X
iptables -t nat -F
iptables -t nat -X
iptables -t mangle -F
iptables -t mangle -X
iptables -P INPUT ACCEPT
iptables -P FORWARD ACCEPT
iptables -P OUTPUT ACCEPT

ip6tables -F
ip6tables -X
ip6tables -t nat -F
ip6tables -t nat -X
ip6tables -t mangle -F
ip6tables -t mangle -X
ip6tables -P INPUT ACCEPT
ip6tables -P FORWARD ACCEPT
ip6tables -P OUTPUT ACCEPT

#chmod +x rc.local

    Then, I rebooted the system. The above script will run, and now I can access my server.

    After everything is ok, then I removed all the above commands to prevent auto run again for the second time.

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