CentOS

That's not a standard CentOS logfile. Chances are that you have a custom entry in /etc/syslog.conf that directs messages to that file and that the syslog daemon still has the file open and thus it's not deleted until it's closed. You probably need to /bin/kill -HUP `cat /var/run/syslogd.pid to have ...

Post the output from lspci -nn | grep -i net and ifconfig -a

Lack of space on /boot or /tmp?

I think you'd be much better served by making sure that you only install things from packages and then keep a list of the packages that you have installed. That makes it easy to recreate your installed apps. Backing up your data is another matter but changing the install path of everything to one be...

lspci -v will show what devices use which loaded device drivers.

I think it's another victim of Redhat trying to force everyone that uses virtualization onto RHEV

EPEL is a third party yum repository with about 10,000 pre-built packages for CentOS 6 already in it. Yum yum install epel-release then yum install asterisk and get a pre-built, pre-tested copy of asterisk, ready to run out of the box.

You could try the nvidia proprietary drivers as repackaged by ELRepo. Install elrepo-release, install nvidia-detect and run it, install the kmod-nvidia package it suggests.

It's unclear if your CentOS 7 system is hosting the samba shares or connecting to them on other systems.

At a guess, you have an initscript which is not designed for use on Redhat based systems. Try hunting round to see if there is one for RH based systems. I checked on a Debian system and that function is present there so what you have now is a Debian initscript.