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I have just setup my CentOS 5.8 64 [final] server as a webserver.

Specs: 2x E5620 Intel CPU, DDR3 RAM, Hardware Adaptec RAID 10, 4x SAS drives.

I have installed myself:

 MySQL [ version]
 Citadel [ddos flood protection]

These are all things that I actively use to run my websites.

Now my question:

I found this article:

Which talks about a whole list of services that you can disable.

This is the list they suggest:

chkconfig anacron off
chkconfig apmd off
chkconfig atd off
chkconfig autofs off
chkconfig cpuspeed off
chkconfig cups off
chkconfig cups-config-daemon off
chkconfig gpm off
chkconfig isdn off
chkconfig netfs off
chkconfig nfslock off
chkconfig openibd off
chkconfig pcmcia off
chkconfig portmap off
chkconfig rawdevices off
chkconfig readahead_early off
chkconfig rpcgssd off
chkconfig rpcidmapd off
chkconfig smartd off
chkconfig xfs off
chkconfig ip6tables off
chkconfig avahi-daemon off
chkconfig firstboot off
chkconfig yum-updatesd off 
chkconfig sendmail off
chkconfig mcstrans off
chkconfig pcscd off
chkconfig bluetooth off
chkconfig hidd off

Now I do use sendmail, and smartd, so those I will keep.

But most of the other processes I do not recognize. Is there anything I should be careful with disabling?

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So what shows up on YOUR system when you do a chkconfig --list|grep -iw on? Do you need iSCSI and iSCSId for instance? cpuspeed might make sense if you want to give your CPUs a rest when there is nothing to do. – Nils Oct 24 '12 at 19:59
up vote 3 down vote accepted

Be careful with using other people's "lists" as you may disable things you actually need.

Some obvious problems I see with that list are:

  • anacron makes sure cron jobs missed due to downtime get run when the system comes back up.
  • smartd monitors the health of your disks and can be set up to email you if a disk is failing (though since you have a hardware RAID, you should use the vendor-provided tool instead).
  • ip6tables is the IPv6 firewall... Really? Somebody advised turning off the firewall?!? This really blows their credibility to hell.
  • yum-updatesd provides automatic updates. If you don't want this, turn it off, though it is useful in some scenarios.

I also have to agree with @aairey's advice to do a minimal install. In CentOS 5, this requires the use of a kickstart file; CentOS 6 has a special minimal installation CD.

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From what I've read, yum-updatesd can be a real mixed bag. One thing I do know for sure is that, if you put a simple cron job that runs yum update (and make sure it runs with a copacetic exit value) the system will be more thoroughly patched than an equivalently-aged quilt. – Parthian Shot Jul 17 '14 at 19:39

While disabling/uninstalling certain software is a perfectly valid approach to hardening a system, in many cases it's overkill -- especially when, like yourself, one isn't certain which services to disable.

The better approach would be to use a minimal installation combined with a restrictive firewall. Since this is going to be a web server, the ruleset should be very easy to define.

To perform a minimal installation, go through the CentOS installer and when you get to the screen that lists roles, uncheck all of them. Then, choose "Customize Now".

You'll see a screen that has various categories on the left and package groups on the right. Go through each category and uncheck all of the package groups. In the Base category, click the Optional packages button. I usually uncheck everything except:

  • anacron allows job scheduling and ensures that scheduled jobs run even if missed due to downtime.
  • sudo allows you to execute commands with elevated privileges from an unprivileged account. In my opinion, this utility is vital for any Linux system.

After the installation is complete and you've rebooted, you can install the web server and any other necessary packages for your situation (httpd, PHP, MySQL, etc). Yum will automatically resolve dependencies for you and should only install those packages that are necessary for your chosen services to function.

When that's complete, edit your iptables rules to only allow necessary services: SSH, HTTP, HTTPS, SMTP outbound, etc. There are many tutorials available that explain how to do this. This question and its accepted answer are a good starting point.

DON'T BLOCK SSH! If you don't have console access to the server, be careful not to block SSH at any point or you'll be unable to access the system. When modifying firewall rules, I always open up a new SSH session without closing my existing (working) one just to verify that I can still connect. Once you exit that established session, if SSH is blocked then you're up the creek without a paddle.

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Did you start of with the minimal install? If not I'd recommend starting there as things like anacron are not even installed to start with.

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Most of these are actually installed and enabled by default: – Mr.Boon Oct 23 '12 at 13:03

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