== Early impressions of CentOS 7

For reasons involving [[us being unimpressed with Ubuntu 14.04
Ubuntu1404Unimpressed]], we're building our second generation iSCSI
backends on top of CentOS 7 (basically because it just came out in
time). We have recently put the first couple of them into production
so now seems a good time to report my early impressions of CentOS 7.

I'll start with the installation, which has impressed me in two
different ways. The first is that it does RAID setup [[the right
way InstallerPartitioning]]: you define filesystems (or swap areas),
tell the installer that you want them to be RAID-1, and it magically
figures everything out and does it right. The second is that it is
the first installer I've ever used that can reliably and cleanly
reinstall itself over an already-installed system (and it's even
easy to tell it how to do this). You would think that this would be
trivial, but I've seen any number of installers explode; a common
failure point in Linux installers is assembling existing RAID arrays
on the disks then failing to completely disassemble them before it
tries to repartition the disks. CentOS 7 has no problems, which is
something that I really appreciate.

(Some installers are so bad that one set of build instructions I
wrote recently started out with 'if these disks have been used
before, completely blank them out with dd beforehand using a live
CD'.)

Some people will react badly to the installer being a graphical one
and also perhaps somewhat confusing. I find it okay but I don't
think it's perfect. It is kind of nice to be able to do steps in
basically whatever order works for you instead of being forced into
a linear order, but on the other hand it's possible to overlook some
things.

After installation, everything has been trouble free so far.  While I
think CentOS 7 still uses NetworkManager it does it far better than [[how
Red Hat Enterprise 6 did RHEL6Dislike]]; in other words the networking
works and I don't particularly notice that it's using NetworkManager
behind the scenes. We can (and do) set things up in
_/etc/sysconfig/network-scripts_ in the traditional manner. CentOS 7
defaults to 'consistent network device naming' but unlike Ubuntu 14.04
it works and the names are generally sane. On [[our hardware
../sysadmin/FutureFileserverHardware]] we get Ethernet device names of
enp1s0f0, enp1s0f1, and enp7s0; the first two are the onboard 10G-T ports
and the third is the add-on 1G card. We can live with that.

(The specific naming scheme that CentOS 7 normally uses is described
in the Red Hat documentation [[here
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Networking_Guide/ch-Consistent_Network_Device_Naming.html]],
which I am sad to note needs JavaScript to really see anything.)

CentOS 7 uses systemd and has mostly converted things away from
_/etc/init.d_ startup scripts. Some people may have an explosive
reaction to this shift but I don't; I've been using systemd on my
Fedora systems for some time and [[I actually like it and think
it's a pretty good init system SystemdRight]] (see also the second
sidebar [[here SystemdAndBrokenByDesign]]). Everything seems to
work in the usual systemd way and I didn't have any particular
problems adding, eg, a serial _getty_. I did quite appreciate that
systemd automatically activated a serial _getty_ based on a serial
console being configured in the kernel command line.

Overall I guess the good news is that I don't have anything much
to say because stuff just works and I haven't run into any unpleasant
surprises. The one thing that stands out is how nice the installer is.