Replace Firewalld with iptables

 Fedora/CentOS7 / RHEL 7  are completely systemd based, So on these versions of Linux we need to use systemd commands to disable firewalld and enable iptables

•  Disable Firewalld Service.

# systemctl mask firewalld

• Stop Firewalld Service.

# systemctl stop firewalld

• Install iptables service related packages.

# yum -y install iptables-services

• Make sure service starts at boot:

# systemctl enable iptables

 If you do not want ip6tables, You can skip following command
# systemctl enable ip6tables

• start the iptables services.

# systemctl start iptables

 If you do not want ip6tables, You can skip following command.
# systemctl start ip6tables

Firewalld Service is now disabled, You can use iptables.

How to Roll back a yum update or a yum install

Easy backout of yum patching


yum install screen
Dependencies Resolved
=================================================================================
 Package          Arch       Version            Repository              Size      
=================================================================================
Installing:
 screen           i686       4.0.3-16.el6       rhel-6-server-rpms      484 k    

Installed:
  screen.i686 0:4.0.3-16.el6
Complete!


Next, identify the transaction ID that we want to 'undo'
type

 yum history
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
ID     | Login user               | Date and time    | Action(s)      | Altered
-------------------------------------------------------------------------------
     8 | root              | 2011-10-03 14:40 | Install        |    1   
     7 | root              | 2011-09-21 04:24 | Install        |    1 ##
     6 | root              | 2011-09-21 04:23 | Install        |    1 ##
     5 | root              | 2011-09-16 13:35 | Install        |    1   
     4 | root              | 2011-09-16 13:33 | Erase          |    1   
     3 | root              | 2011-09-14 14:36 | Install        |    1   
     2 | root              | 2011-09-12 15:48 | I, U           |   80   
     1 | System           | 2011-09-12 14:57 | Install        | 1025  
The transaction ID we are interested in is '8', so move forward with undo step. If want to see additional information to verify this is transaction interested in, use yum history info 8 prior to doing the undo

 yum history undo 8
Loaded plugins: product-id, refresh-packagekit, subscription-manager
Updating Red Hat repositories.
Undoing transaction 8, from Mon Oct  3 14:40:01 2011
    Install screen-4.0.3-16.el6.i686
Resolving Dependencies
--> Running transaction check
---> Package screen.i686 0:4.0.3-16.el6 will be erased
--> Finished Dependency Resolution

Dependencies Resolved
================================================================================
 Package          Arch       Version            Repository              Size
================================================================================
Removing:
 screen           i686       4.0.3-16.el6       @rhel-6-server-rpms     783 k

Removed:
  screen.i686 0:4.0.3-16.el6
Complete!