CentOS 7 and Chef

CentOS 7 is centrally supported at SLAC for the following platforms:

• VMware virtual machine
• OpenStack virtual machine
• Bare metal server
• Desktop productivity - under development.  If you wish to help testing, email unix-admin@slac.stanford.edu

Although RHEL 7 is also available if required by your application for support, CentOS 7 is preferred and recommended instead.  Any instructions below for CentOS 7 also apply for RHEL 7.

Step-by-step guide

These are the steps to install and configure CentOS 7 with Chef at SLAC for a headless bare metal server.
To request a CentOS 7 virtual machine (VM) in VMware or OpenStack, please email unix-admin@slac.stanford.edu .

1. Install CentOS 7 using either the Minimal or the DVD ISO available here (available on the SLAC network or VPN).  The ISO image can also be used for a USB key install.

   http://yum.slac.stanford.edu/iso/centos/7

    

2. Log into your new CentOS 7 host. 
   Become root by using sudo or /bin/su. 
   Install Chef on bare metal or a VM by running this command as root:

   curl -s http://yum.slac.stanford.edu/go-chef | /bin/sh

   If you want to only configure yum, and not run any of the other Chef recipes, then don't run the above command, run this instead:

   curl -s http://yum.slac.stanford.edu/go-chef  |  sed -e 's/^chef-client.*/chef-client -r recipe[slac_yum]/'  |  /bin/sh

   That command is using 'sed' to replace the last line of the go-chef script.  Note these instructions are subject to frequent change, so please check back to this page for the most recent version. Configuring only yum, and nothing else, means that your CentOS 7 host is unmodified except it can now apply yum updates, even if your machine is on a private 172.X subnet.

3. Before you exit your root prompt, you need to modify this file:

   /etc/security/access.netgroup.conf

   Add a line that looks like this (replace 'ksa' with your username):

   + : ksa : ALL

   Make sure to add that line above the last line.  Here is an example of what the file might look like if you wanted to grant login access to SLAC users ksa and vanilla:

   + : root : LOCAL  134.79.0.0/16 172.16.0.0/12
   + : ksa : ALL
   + : vanilla : ALL
   + : @u-scs-staff : ALL
   - : ALL : ALL

    

4. And still before you exit your root prompt, create a sudoers entry for yourself inside the /etc/sudoers.d directory.
   If you do not want or need sudo access, you can skip this step.
   
   You can copy and paste the following (replace 'ksa' with your username):

   cat > /etc/sudoers.d/user-ksa << EOF
   ksa   ALL=ALL
   EOF

   Be sure to read and fill out the sudo request form.  This is required for auditing purposes:
   https://www.slac.stanford.edu/comp/unix/auth/superuser-req.shtml

    

5. If you would like a Kerberos host keytab installed on your CentOS 7 host, send an email to unix-admin@slac.stanford.edu .
   Without a Kerberos host keytab, you will need to enter your SLAC password when connecting via ssh, even when you already have a Kerberos ticket granting ticket (TGT).  If you have unix-admin install a Kerberos host keytab, then you can use passwordless GSSPAI via ssh to connect without a password when you already have a Kerberos TGT.
   
   

Soon we will run the chef client as a daemon, but at the moment the go-chef command is a one-time configuration script, which will not install a cron job or a daemon to run chef periodically.  This is because we do not want to overwrite the access.netgroup.conf file and remove any modification you have made to the user login list.  Soon we will have your user login list maintained by Chef, but we are still working on that now.

After you install Chef using the go-chef script, your CentOS 7 host will be configured for central authentication using Unix Kerberos.

In addition, here is an incomplete list of the configuration items that will be configured by Chef (just to give you an idea):

• cron
• logrotate
• rsyslog
• /etc/motd
• root password
• kerberos
• ssh
• shells
• sssd
• ntp
• yum
• yum-cron
• sudo for unix-admin
• login access for unix-admin

These are the configuration items Scientific Computing Services (SCS) is working on next:

• AFS client
• Automated keytab installation (for passwordless ssh connections)
• NFS client
• grub2 configuration for bare metal server installation
• login access for users
• sudo access for users
• GDM login on video console for a desktop

In addition, the SLAC Desktop Support team are currently testing CentOS 7 on their lab machines. 

Scope of Support for CentOS 7 on the Desktop

CentOS 7 on the desktop should be thought of as a personal productivity machine, not a development or server. Development machines and servers can be hosted in virtual machines or bare metal machines in servers rooms. Virtualization platforms available include OpenStack, VMware, and (in the future) Amazon Web Services public cloud. AWS for SLAC use is currently being tested.

List of supported personal applications by the HelpDesk Desktop Support Team are standard RPM packages supported by Red Hat (in progress – this is not a complete list)

List of recommended yum repositories. We do not recommend adding any yum repository other than the ones listed below.

Do not install these repositories: ATrpms, RPMForge, RepoForge. Those repositories do not play well with RHEL or CentOS. You will likely break your system due to distribution RPMs being replaced by the third party RPMs, and therefore causing rpm dependency problems. If you need RPMs or software that you cannot find in the recommended repositories above, email unix-admin@slac.stanford.edu for advice.

Frequently Asked Questions:

Please send any questions to unix-admin@slac.stanford.edu