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  ::

dnstop – top like utility for Fedora and other *nix

For installation :

sudo yum install dnstop

And now some description:

dnstop is a libpcap application (ala tcpdump) that displays various
tables of DNS traffic on your network.

dnstop supports both IPv4 and IPv6 addresses.

To help find especially undesirable DNS queries, dnstop provides a
number of filters.

dnstop can either read packets from the live capture device, or from a
tcpdump savefile.

Couple of days back, I realized there was too much network activity on my
system, although I was not doing anything. Fired up wireshark and to my
astonishment, there was too much of DNS traffic on the network. But the
problem was analyzing the data in wireshark and this is where dnstop came
into light. It helped me narrow down the issue within minutes and problems
resolved.

snmpd -verify if the mibs are loaded.

If you are setting up the snmpd server and have added your own mibs and do not really know if the mibs are loaded or not then simply go to the directory:

/var/lib/net-snmp/mib-indexes

This can save you a lot of time, if you are not getting results with snmpwalk. You can even use snmpwalk as :

snmpwalk -v  -c

Well, these little things can save you a lot of time 🙂

ss – utility to investigate sockets.

Sometimes, you find some interesting application/command by accident, and that is just what happened a few days back. Well, I was doing a ssh and as usual made my share of mistake in typing and missed the “h” from the ssh command and saw a list of options instead of my prompt on remote server.

Now, that set me thinking and fond that its a very interesting command that comes with iproute on Fedoara, so if you want this command, then install iproute like this