[CS-FSLUG] Centos 7

Tim Young Tim.Young at LightSys.org
Fri Jul 18 11:29:27 CDT 2014

To add some Linux traffic to the list...

Centos 7 has recently come out, and I am fiddling my way through 
it.   There are a number of things that surprised me.

MariaDB replaces mysql.  MariaDB is a fork of mysql with some of the 
original developers.  Oracle is doing some things in a 
not-so-friendly to open-source way with mysql, so a number of distros 
are making this leap.  MariaDB is supposed to be entirely compatible 
with mysql, but will have some additional options that mysql does not 

systemd has replaced init / upstart scripts.  So all the startup 
scripts are quite different than they were before; living in 
different directories and not using bash scripts to handle things.  
systemd also does logging, so some distros will no longer have their 
main logging go to /var/log and be textfiles.  For people who have 
made their own daemons in the past, there are some things systemd 
assumes which may require you to make changes to your programs.

Centos used to use Lokkit, and are switching to firewalld.  That is a 
fairly substantial change.  It is still iptables based, but it has 
some odd ramifications for how things are done.  Firewalld lets you 
make changes to your firewall that are persistent or temporary.  
Usually configuration is done by making changes to config files 
instead of having them done programatically.

NetworkManager got put in the mainstream of Centos6, but is even 
more-so in Centos 7.  NetworkManager is supposed to do a better job 
in dealing with mobility; when you change location, it adjusts the IP 
configuration to match.  This is great for laptops, but is a little 
awkward for servers.  Anyway, most of the network configuration is 
now done with the "nmcli" command.

Which leads me to the depressing news that Centos has finally done 
away with ifconfig, arp, netstat, mii-diag, route and a number of the 
other "standard" network tools.  You can still install the net-tools 
package, but those commands have mainly been replaced by "ip."  This 
is a bit of a break because most of those other tools come default on 
Windows computers (though with slightly different names)  I always 
looked really awesome when, as a Linux techie, I could sit at a 
command-prompt of a Windows machine and determine what was going on 
with their network faster than they could from the GUI.  Now I will 
need to resurrect my non-linux command-set to look so smart.  Drat.

Centos also uses xfs by default.  I have not run into anything with 
that, but I know there are a number of things I used to take for 
granted with the ext[2,3,4] filesystem that I will need to revisit.

They have also jumped kernels to the 3.x series instead of the 
2.4/2.6 kernels.  I have not yet begun to look into what the 
difference in the kernel is.

I have really enjoyed how chrony keeps my VMs time to be correct. I 
have no idea how well that will scale.  ntp creates a lot of network 
traffic, and suddenly having a lot of boxes checking ntp on a much 
more regular basis may cause a lot of the ntp servers to go away.  
But it is a very nice service to have running on my Virtual Machine!

Anyway.  It will be interesting to see how Centos 7 pans out.  For 
myself, I will need to update all sorts of training materials that we 
have built to incorporate all this new stuff.

     - Tim Young

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