Jan 20

Linux Foundation exam updates.

The Linux Foundation is making some adjustments to its LFCS and LFCE exams starting on March 1, 2015:

  • in the LFCS exam objectives, RAID is replaced with LVM,
  • in the LFCS exam, the pass mark becomes 74% (instead of 65%),
  • in the LFCE exam, the pass mark is now 72% (instead of 65%),
  • some updates to security protocols occur,
  • the exam interface’s got some improvements.

Perhaps in response to the Red Hat RHCE 7 exam hardening, the Linux Foundation makes its exams more difficult to get by raising their pass mark: an exam too easy to pass doesn’t get good publicity nor doesn’t trigger good training sales.

Sources: Linux Foundation LFCS & LFCE pages.

Jan 12

Postfix tips.

When dealing with SMTP for the RHCE or LFCE exams, there are some tips that can be very useful to know about Postfix.

First, you’ve got a very interesting website at http://www.postfix.org/postfix-manuals.html.

Then, during the exam, you can get some configuration examples in the /usr/share/doc/postfix-2.10.1/README_FILES directory for RHEL 7 (-/postfix-2.6.6/README_FILES for RHEL 6) in the BASIC_CONFIGURATION_README and STANDARD_CONFIGURATION_README files. This documentation comes with the postfix package.

In addition, the /etc/postfix/main.cf file, the main configuration file, is fully documented. This will help you decide what parameter to change.

But there are more to know!
You’ve got the choice to edit the /etc/postfix/main.cf file or to use the very powerful postconf command. Instead of wasting time, searching for the Postfix parameter in the main.cf file, if you know its name, you can directly assign a value to it or get its value:

# postconf -e 'relayhost=[192.168.1.1]'
# postconf relayhost
relayhost = [192.168.1.1]

This is not only very efficient, but the configuration is also definitively written in the main.cf file!
You can restart the Postfix processes or even reboot the server, it’s still there.

Also, by using the relayhost = [192.168.1.1] syntax during your test, you can avoid the use of a master DNS server and its associated MX record (MaileXchange), which can be very handy.

Finally, at any time, you can check the syntax of the main.cf file with the postfix check command.
You can also get the list of the parameters with non-default assigned values with the postconf -n command.

In conclusion, Postfix is really a powerful and well designed tool.

Dec 01

RHCSA & RHCE 6 last call.

If you plan to take the RHCSA 6 or RHCE 6 exams, you’ve got to hurry because these exams will be withdrawn in two to three weeks.

As RHCSA 7 is not too different from RHCSA 6, it will not be too painful if you miss the date.

It’s going to be an other song if you wanted to take the RHCE 6 exam, because the v7 is an other world: you will have to start almost from scratch! Firstly, it’s now 3.5 hours instead of 2. Secondly, topics are different: network (teaming, bonding, ipv6, etc), Kerberos (NFS+Samba), security (firewalld), storage (iSCSI), and database (MariaDB).

If you thought about taking the RHCE 6 exam, book it now and work hard to pass it at the first attempt!

Nov 18

Yum transaction history.

Since RHEL 6, a transaction history has been added to the yum command.
This feature allows you to precisely know which packages have been installed on a server and in which order.
In addition, you can undo or redo any of the previous package installations.
Finally, by comparing the rpmdb version of two servers, you can verify if the exact same packages have been installed on both of them, which can be useful when moving from development to production environments.
To get into the details, check the tutorial about using the yum transaction history.

Oct 25

RHEL 7 SELinux additional man pages.

In one of his latest videos Sander van Vugt shows us that some SELinux information is not available without some tricky operations.

Actually, after a standard RHEL 7 / CentOS 7 installation, only basic SELinux man pages are installed. All the SELinux man pages dealing with applications (httpd, vsftpd, etc) need an additional work to be accessible.

Now, you’ve got two options: watch Sander van Vugt’s video or access my dedicated tutorial about deploying additional SELinux man pages. It’s up to you!