configure firewall – the easy way.

It is good practice to keep iptables/firewall enabled. But configuring it is difficult, do you agree. Not any more 🙂

Install firewall-config

sudo yum install firewall-config

This will install a GUI application, which you can run with “Firewall” application in the dash or with “firewall-config” in terminal. It is pretty straight forward to use this tool, even if you don’t have much knowledge on Firewall/iptables.

sendmail or sending mail

If you want to use sendmail so that you can send all your mails from the local system to your email address, then you have to use sendmail.  Now, configuring sendmail has never been that easy and if you are working internally on your corporate network then for sending mails to the same domain, generally you don’t have to login. That being the case, you can use something simpler like “sstmp“. Install ssmtp with:

ss – anothre utility to investigate sockets.

ss is :

ss  is  used to dump socket statistics. It allows showing information similar to netstat.  It can display more TCP and state informationsthan other tools.

 

This comes in iproute package in Fedora. So, to install this you would need to install “iproute” if not installed already.

sudo yum install iproute

Now, once you have done that you can look at the man page to check what all you can see with ss. but here are some examples:

dnsmasq not starting from NetworkManager with SELinux enabled.

Some time back I posted on dnsmasq starting from Network Manager and how to setup dnsmasq.

Now, couple of days back , I setup dnsmasq in NetworkManager but was astonished to see that there was no dnsmasq running. I checked with dig and saw that there was no response from localhost for dns queries. Checked “ps -eaf|grep dns” and found that there was no dnsmasq running. I knew that once you mention “dns=dnsmasq” in the NetworkManager then it should start up but that was not happening. And then I checked audit log, found that some permissions were denied by SELinux.

slow ssh connection

If you are experiencing slow ssh connections, then possibly your system is trying to do reverse lookup of the IP address. If that is the case, then you can add the below to “hosts” line in /etc/nsswitch.conf file.

‘[NOTFOUND=return]’

The other cause for slow connections can be GSSAPI authentication. If that is the case, then the simplest solution is to add the following in your “~/.ssh/config” file:

ssh reverse tunning..

If you want to access some local resources like the release website from the remote server when you are connecting to the remoter server using ssh over VPN, then possibly reverse ssh tunnelling is the best option. So, basically when you are connecting to the remote server, you tell the server your intent to do so and which local resource you want to connect to and on which port.So, here I want to connnet to google.com and tunnel the data to 192.168.131.921:9090 tthough the tunnel, then the command to use will be  ::

dnsmasq – use with Network Manager.

Well if you have not heard about dnsmasq:

Dnsmasq is lightweight, easy to configure DNS forwarder and DHCP server.
It is designed to provide DNS and, optionally, DHCP, to a small network.
It can serve the names of local machines which are not in the global
DNS. The DHCP server integrates with the DNS server and allows machines
with DHCP-allocated addresses to appear in the DNS with names configured
either in each host or in a central configuration file. Dnsmasq supports
static and dynamic DHCP leases and BOOTP for network booting of diskless
machines.

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