Synthetic view of a server.

To harden a server or simply reduce its security footprint, it is very useful to get a list of the main processes running. However, it is not an obvious task to get a synthetic view like this.

Using a command like ps -edf brings too much information and doesn’t really help you.

I recently came across the pstree command and found it quite useful.

First, install the psmisc package available in the base repository:

# yum install -y psmisc

Then, execute the pstree command:

# pstree
systemd─┬─NetworkManager───2*[{NetworkManager}]
        ├─abrt-watch-log
        ├─abrtd
        ├─2*[agetty]
        ├─atd
        ├─auditd───{auditd}
        ├─chronyd
        ├─crond
        ├─dbus-daemon───{dbus-daemon}
        ├─firewalld───{firewalld}
        ├─httpd───6*[httpd]
        ├─lsmd
        ├─lvmetad
        ├─master─┬─pickup
        │        └─qmgr
        ├─polkitd───5*[{polkitd}]
        ├─rngd
        ├─rsyslogd───2*[{rsyslogd}]
        ├─smartd
        ├─sshd─┬─sshd───bash───pstree
        │      └─sshd───sshd
        ├─systemd-journal
        ├─systemd-logind
        ├─systemd-udevd
        └─tuned───4*[{tuned}]

As the test was performed on a virtual machine, I could quickly see that the smartd daemon (part of the smartmontools package) was running. This daemon monitors disk health: this is completely useless in a virtual environment where all disks are already managed by the host or a dedicated storage subsystem.

# systemctl disable --now smartd
# yum remove -y smartmontools

I hope you find this tool as useful as I found it.

Posted in RHEL7

RHEL 7.4 officially released.

Today, Red Hat announced the official release of RHEL 7.4.

To know more about this new version you can read a summary of the RHEL 7.4 changes or the RHEL 7.4 Release Notes.

Several points can be highlighted:

  • docker overlay graph driver with SELinux in enforcing mode is now supported,
  • OpenSSL update (1.0.2k) brings support for ALPN & native HTTP/2,
  • System Security Services Daemon (SSSD) in a container is now fully supported,
  • Identity Management (IdM) server container is available as a Technology Preview feature,
  • OpenLDAP & Btrfs are deprecated and will be removed in future RHEL major versions.
Posted in RHEL7

Latest technical articles.

Over the past two weeks, the following technical articles have been published (or discovered):

Happy reading!

Posted in Others

New recent articles.

Many technical articles were published in the last two months:

Happy reading!

Note: Two objectives have recently been removed from the RHCSA exam:

  • Install RHEL using Kickstart,
  • Configure a physical machine to host virtual guests.

This means that you don’t need to learn KVM or Kickstart anymore to pass the RHCSA exam, using Virtual Box is enough.

Posted in Others

Available online Linux trainings.

Until one or two years there was almost no online trainings for the RHCSA & RHCE 7 certifications.

You had to take Red Hat classes or study by yourself through books.

Now, companies like EdX, Udemy and LinuxAcademy to name some of the most known have started to create good contents.

You can now find most of them in the dedicated RHEL 7 online training page.

Happy trainings!

Posted in RHEL7

Atomic Host.

If you like containers, at some point you will deploy them into production. And you will need a dedicated server to host them.
Atomic Host is the RedHat solution for this.
It is a lightweight version of RHEL/CentOS 7 (there is also a Fedora version) where :

  • only the /etc and /var directories are writable,
  • all the OS can be upgraded or rolled back atomically (hence the name) through the rpm-ostree mechanism,
  • there is no yum command nor man pages.

Take the time to discover this new animal through the Atomic Host tutorial.

Posted in RHEL7

RHEL 7 CPU governor.

I don’t know if you have already heard about CPU governor.

With the global warming, IT culture should integrate the various mechanisms available for reducing computer consumption.
In a perfect world, during the idle periods servers should adjust their clock frequency to get significant power saving. They should even stop through some scalability mechanisms if possible.

If you think a better understanding of technology can help our earth, have a look at the CPU governor tutorial.

Posted in RHEL7

RHEL 7.4 planned features and other news.

At the Red Hat annual summit the main planned features of RHEL 7.4 were disclosed.
You can find them in a dedicated page.
In addition, as of today, the RHEL 7.4 Beta has been released. Release notes are available here.

Also, new interesting Red Hat summit presentations were published this week:

Similarly, new Red Hat summit videos were released:

Of particular interest for exam candidates two labs were published:

Finally, several technical articles were recently posted:

Happy reading, watching, and labbing!

Posted in RHEL7

Red Hat Summit 2017.

The annual Red Hat summit 2017 happened last week.
The first videos are available on the Red Hat summit channel on Youtube.

Some presentations have already been published about:

Besides presentations you can also practice through:

More videos will progressively be released but be patient: last year it took Red Hat 3 months to publish most of the Red Hat Summit 2016 videos due to a problem with one of its subcontractors!

Posted in RHEL7

Do you know Cockpit?

Until recently I didn’t know what was exactly the Cockpit project.

I thought it was a new complicated panel for administrators looking for a GUI.

Difficult to install, to maintain, to understand …

In fact, it is just the contrary: easy to use with a zero memory and process footprint!

Take the time to discover the Cockpit project through the Cockpit tutorial, you won’t be disappointed.

Posted in RHEL7

RHCSA7: Task of the day

Allowed time: 5 minutes.
Create a new user account called "bob" with password "redhat" and set expiration in one week.

RHCE7: Task of the day

Allowed time: 10 minutes.
Set up a default secure MariaDB database called maria and back up the database with mysqldump.

Poll for favorite RHEL 7 book

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