Linux How To: Install IPTABLES in CentOS 7 / RHEL 7 Replacing FirewallD

CentOS 7 / RHEL 7 doesn’t come with iptables by default. It uses a full functional firewall system called ‘firewalld’. I have been a big fan of iptables and it’s capability from the very first, and since I have switched to CentOS 7, I couldn’t stop using it. I had to stop firewalld and install iptables in all of my CentOS 7 installation and start using iptables rules as I was using before. Here is a small How To guide on installing Iptables and disabling firewalld from a CentOS 7 or RHEL 7 or a similar variant distro.

How to Install IPTABLES in CentOS 7

To begin using iptables, you need to download and install iptables-service package from the repo. It isn’t installed automatically on CentOS 7. To do that, run the following command:

# yum install iptables-services -y

How to stop the firewalld service and start the Iptables service

Once the iptables-serivces package is installed, you can now stop the firewalld and start the iptables. Keeping both kind of network filtering too can create conflicts and it is recommended to use any out of two. To do that run the following:

# systemctl stop firewalld
# systemctl start iptables

Now to disable firewalld from the starting after the boot, you need to disable the firewalld:

# systemctl disable firewalld

To disallow starting firewalld manually as well, you can mask it:

# systemctl mask firewalld

Now you can enable iptables to start at the boot time by enabling iptables using systemctl command:

# systemctl enable iptables

How to check status of iptables in centOS 7

In previous distros, iptables status could be fetched using service command, although, the option is no longer available in CentOS 7. To fetch the iptables status, use the following:

# iptables -S

Iptables save command can still be used using service tool:

# service iptables save

This would save your iptables rules to /etc/sysconfig/iptables as it used to do in previous distros.

Quick Tip: How to view public IP using SSH terminal/cURL/wget

There are times when you might require to view the IP address your server is using for outgoing connections. If you are in command line/console/mosh/ssh/rsh, you want an one command solution instead of visiting a page like whatismyip.com using lynx browser or so on. Here is a quick tip that I regularly use to perform this:

Using cURL:

curl ifconfig.co

Using wget:

wget -qO- ifconfig.co

ifconfig.co does it simple and easy.

Check File System for Errors with Status/Progress Bar

File system check can be tedious sometimes. User may want to check the progress of the fsck, which is not enabled by default. To do that, add -C (capital C) with the fsck command.

fsck -C /dev/sda1

The original argument is:

fsck -C0 /dev/sda1

Although, it would work without number if you put the -C in front of other arguments, like -f (forcing the file system check) -y (yes to auto repair). A usable fsck command could be the following:

fsck -fy -C0 /dev/sda1

or

fsck -C -fy /dev/sda1

Please note, -c (small C) would result a read only test. This test will try to read all the blocks in the disk and see if it is able to read them or not. It is done through a program called ‘badblock’. If you are running badblock test on a large system, be ready to spend a large amount of time for that.