What’s new with NetworkManager?

NetworkManager big update

From RHEL 7.2 to RHEL 7.3, NetworkManager moved from v1.0.6 to v1.4.0: a lot of things have changed.

Color is everywhere!

Use of colors in NetworkManager
NetworkManager now uses colors to match the status of a device or a connection and sorts the output for better clarity.


nmcli with ifconfig style
Invoking nmcli without argument displays all the network interfaces with an ifconfig style.

Also, connection add syntax is now consistent with connection modify.

Clever completion

When asking for completion, NetworkManager doesn’t propose inappropriate argument anymore: here the connection called Hotspot can’t be chosen because already inactive.

# nmcli con down [tab]
apath     id        path      virbr0    vlan40
help      Internet  uuid      vlan30


You need a bridge over VLAN? Software devices (bond, bridge, vlan, team, …) can now be stacked arbitrarily. The nmcli interface for creating master-slave relationships has been significantly improved by the use of ‘master’ argument to all link types.

IPv6 security improvements

IPv6 connection properties have been added like:

  • ipv6.addr-gen-mode: the stable privacy addressing is a tracking prevention mechanism implementing the RFC7217 (more details here); when enabled the property takes stable-privacy as value and eui64 when disabled,
  • ipv6.ip6-privacy: the privacy extension is a way to randomize MAC address as defined by the RFC4941 (more details here and here); when enabled the property takes 1 and 0 otherwise.

Wi-Fi improvements

  • Better security: several options have been added concerning the exposed MAC address of a Wi-Fi device during the scanning phase and after (see details here).
    The 802-11-wireless.cloned-mac-address property can now receive the following values:

    • A MAC address: this was already supported before 1.4.0 and allows to spoof a specific MAC address.
    • permanent: use the permanent MAC address of the device. Before 1.4.0, the permanent MAC address was used if the cloned-mac-address property was left empty, thus it was the default. In 1.4.0, it is still the default.
    • preserve: don’t change the MAC address of the device upon activation.
    • random: generate a randomized value upon each connect.
    • stable: generate a stable, hashed MAC address.
  • Better Wi-Fi scanning: with recent versions of wpa_supplicant, NetworkManager scanning behavior has been improved (see details here).
  • Wi-Fi power saving: Wi-Fi power saving can now be enabled globally or on a per-connection basis.

Various improvements

  • Support for more devices: NetworkManager can now manage tun, tap, macvlan, vxlan and IP tunnel devices.
  • More flexible VPN support: Many previous VPN restrictions have been removed. You can now import and export the VPN connection settings of most types of VPNs in the VPN’s native format using the nmcli connection export and nmcli connection import commands.
  • Compatibility with namespace-based containers: NetworkManager now runs fine in LXC and Docker.
  • Hostname management: hostname is now managed via systemd-hostnamed.
  • DHCP: timeout for DHCP requests can now be modified using the ipv4.dhcp-timeout property.
  • IPv4: support for detecting duplicate IPv4 addresses, with a timeout configurable through the ipv4.dad-timeout connection property, is now available.
  • Rollback: API for using configuration snapshots that automatically roll back after a timeout has been added. A remote network configuration tools like Cockpit can use this new feature to avoid situations where a mistake in the configuration makes the remote host unreachable.
  • DNS client: A new dns-priority property of ipv4 and ipv6 settings can be used to tweak the order of servers in resolv.conf. This will make things easier for users who often use multiple active connections.
  • Bandwidth monitoring: RX/TX counters of transferred bytes per interface are now exposed on D-Bus. With this, client applications can monitor the bandwidth.

There are still other improvements but they are too many to be all listed here!


Additional Resources

You can also read this Red Hat Article about setting up MACsec using wpa_supplicant and NetworkManager.
Support for OpenVSwitch bridge, bond and VLAN has been added to NetworkManager but is still not integrated in the RHEL 7.4 release.

Posted in RHEL7

What’s new with RHEL 7 CGroups?

Since RHEL 6, CGroups have been a work in progress. So, in RHEL 7 features evolved through new Systemd commands like systemd-cgls, systemd-cgtop, and mainly systemctl set-property.

Still through Systemd, RHEL 7.0 brought the CPUShares (percentage of CPU), MemoryLimit (memory quota), and BlockIOWeight (percentage of block IO) main properties, allowing you to set some constraints on system resources.

RHEL 7.2 added StartupCPUShares, StartupBlockIOWeight, and most importantly CPUQuota.

Marc Richter, Technical Account Manager at Red Hat, recently published a series of articles helping you better understand CGroups:

But CGroups are still evolving: Chris Down from Facebook presented the new CGroupsv2 interface at the 2017 FOSDEM conference at the beginning of February. This new interface changes the way the CGroups hierarchy works and globally removes several existing inconsistencies. This interface is stable since the kernel 4.5 and requires a recent version of Systemd (>=v226) not available in RHEL 7 until now (but unofficial options exist).

As usual, you can find all these details and more at the CGroups page.

Posted in RHEL7

RHEL 6.9 just released.

The RHEL 6.9 distribution has just been released and brings the following main benefits:

  • TLS 1.2 support has been added to all system components,
  • several SSSD improvements have been made in connection with AD forests and PAM services,
  • the cpuid utility is now available and dumps detailed information about the CPU(s) gathered from the CPUID instruction. It supports Intel, AMD, and VIA CPUs.

You will find all the details in the RHEL 6.9 Releases Notes & RHEL 6.9 Technical Notes.

In addition, on May 10, 2017, Red Hat Enterprise Linux 6 enters Production Phase 3, meaning that subsequent updates to Red Hat Enterprise Linux 6 will be limited to qualified critical security fixes and business-impacting urgent issues.

Finally, according to the Red Hat Enterprise Linux lifecycle, RHEL 6 will be supported until at least November 2020.

Posted in RHEL6

Death of Docker?

Back in September 2016, an event went unnoticed, although it was a fundamental change. Google and RedHat declared the game is over: they decided to fork Docker.

Why did they decide to do that?

Redhat had several reasons:

  • Container conception: Solomon Hykes from Docker couldn’t agree with Lennart ‘Systemd’ Poettering from RedHat on the container vision,
  • Container security: frustration in the RedHat security team was high because of difficulties to integrate patches into the Docker product,
  • Container stability: the Docker company was always adding new features based on new Linux kernels into its product, triggering an insane amount of work to backport all these features into the 3.10 kernel used by most of RedHat products (RHEL 7, Atomic, OpenShift, etc),
  • Container support: the Docker company didn’t consider compatibilities between versions a priority and problems regularly occurred, this didn’t please RedHat that makes a living by supporting customers.

On the Google‘s side, things were even easier to understand. The company has been working on an in-house orchestrator called Kubernetes for years and wanted it to be at the heart of all the container ecosystem. When Google‘s team heard that the Docker company was promoting its own product named Swarm as reference orchestrator, the decision to fork was almost made.

At the end of January 2017 at DevConf.cz, Dan Walsh from RedHat gave a very interesting presentation about Containers in Production (container standardization, read-only container images, CRI-O, COW filesystem problems, etc). At 40 minutes from the beginning, he acknowledged that the Docker replacement was in the testing stage.

At first called OCID, then renamed CRI-O, it already owns its logo. Fully compatible at the format level with Docker, this new Open Source product will bring its own set of tools like skopeo to get an image from a container registry.

If for developers things may continue as usual, in production environments you should see the following change in the coming months:

RedHat people never say that CRI-O is a Docker replacement, they only say they are building an alternative option that will become their reference solution …

Now, you can’t say you didn’t know.

Posted in Others

New interesting articles.

Several technical articles were recently published:

Happy reading!

Posted in RHEL7

New interesting videos

If you are new to OpenStack and want to get some basic knowledge about it, Red Hat recently published three interesting videos:

Also, FOSDEM 2017 happened last week publishing a lot of interesting videos (the list is available here).

Among all these videos, some are very interesting:

Still about FOSDEM 2017, if you are interested in databases, you will certainly find some useful information in these pages:

Enjoy watching!

Posted in Others

2017 DevConf.cz interesting videos

Last week was organized the free annual community conference for developers, admins, and users of Open Source technologies called DevConf.cz. The conference happened over three days in Czech Republic at Brno.

Around 170 workshops were recorded, sorted according to the following categories: JUDcon (software development), Virtualization, Linux, Containers, OpenStack, Fedora, DevOps, Cloud, Testing, ConfigMgmt, Agile, OpenShift, Security, .net, Networking, Storage, Meetups and DevTools.

A description of all the workshops is available here. All the recordings can be watched on YouTube here.

Among all these videos, here is a selection that can interest you:


Posted in Others

Python dependency hell.

At the beginning there was the Bourne Shell. Then, Perl was created to better deal with character strings and regular expressions.

Linux came and the Bourne Shell was replaced with Bash (Bourne Again SHell) with many built-in features like integer arithmetic.

Because of its unusual syntax and its lack of object-oriented capabilities, Perl is now replaced with Python.

Today, Python is almost everywhere: tools like yum, tuned or Firewalld are all written in Python.

As the CPAN (Comprehensive Perl Archive Network) offered an incredible number of modules for Perl, Python modules have also been created to provide additional features.

They can be installed through RPM packages or with the pip install command.

Here is a potential problem. When you install a Python module through an RPM package, you get all the work done by the maintainer behind (RedHat, CentOS, EPEL, etc) to make sure that this module and all its dependencies will work fine together.

On the contrary, when you run the pip install command, you don’t know where the Python module will be installed and what exact dependency will be activated. In my experience, this doesn’t work very well. You can get the same Python module in different versions on the same server. In this situation, everything becomes very complicated. And this is not a RHEL/CentOS specific problem but concerns most of the Linux distributions (see details for Ubuntu here).

Furthermore, the pip install method sometimes requests that you compile modules locally. To compile Python modules, you need to install the gcc compiler: this is not a good practice in a production environment.

Conclusion: If you are not an expert in Python, stay away from the pip install command.

Posted in Others

New interesting articles.

There were several interesting articles recently published:

Happy reading!

Posted in Others

Happy new year 2017!

This week was the opportunity for two new tutorials:

I wish you a happy new year 2017 and a lot of success in everything you try!

Posted in Others

RHCSA7: Task of the day

Allowed time: 10 minutes.
Create an EXT4 file system mounted by UUID in /etc/fstab under /vol based on a logical volume of 28 logical extents.

RHCE7: Task of the day

Allowed time: 8 minutes.
Set up an iScsi target based on a block backstore of 100MB called lv_iscsi with basic authentication, ext4 filesystem and standard firewall configuration.

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