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CentOS Blog: YUM4/DNF for CentOS 7 updates

2018, April 17 - 07:39

I am pleased to announce some significant updates to our ConfigManagement Special Interest Group for YUM4.  This provides YUM4, based on DNF technology, for testing on CentOS Linux 7/x86_64.  These updates are based on feedback from our prior test release last October. It includes signed packages, core DNF plugins, and uses a version of RPM very similar to and compatible with the upcoming version of CentOS 7.5.

This initiative is based on a partnership with the upstream YUM and DNF maintainers for the future of package management.  Our testing thus far indicates no major problems, but we would love to find out how it fits into your existing YUM 3 workflows. So please consider filling out the short survey - your feedback helps us all get better.

YUM 4 provides significant improvements such as fast dependency resolution and a stable, documented API. See the references below for detailed improvements. We have made every effort to preserve the existing end-user experience that is available with YUM 3. This is the primary reason for making YUM 4 available for testing now.

“What’s with the YUM4 name?”

We recognize that we need to enable users to test YUM4 (/usr/bin/yum4) within their existing workflows in order to fully understand compatibility while retaining YUM version 3 (/usr/bin/yum) as the default.  Yes, they can both be used on the same system, switching back and forth.  We do not recommend this behavior, but it should work with the only known issue being that each version retains its own separate history.  So using the Rollback capability is not recommended as each version will not be aware of the other’s history. Note that the YUM4 name is temporary for the coexistence of versions 3 & 4.

“So, what all has changed?”

The documentation does a great job explaining the differences in great detail. In short, your existing experience using yum to install, remove, and update are identical. However, there are changes such as some of the plugins and yum utilities are now consolidated into `dnf-plugins-core`. Some of the yum CLI options changed and are either converted for you automatically or silently ignored when that behavior is automatically included. Existing custom plugins written for YUM 3 will not work with YUM 4. Please reference the DNF API Reference and Changes in DNF hook API compared to YUM 3 links for further information.

“I found a bug, what should I do?”

Please report any found bugs on Red Hat Bugzilla against Fedora/dnf component (make sure to mention versions and that you use package from CentOS).

And remember to submit feedback in the short survey to help us understand how it can be improved further.

“Three step install, get started right away” # yum install centos-release-yum4 # yum install yum4 # yum4 install dnf-plugins-core “I was already testing a previous version of YUM4.  How do I update?” # yum4 update centos-release-yum4 # yum4 update yum4

 

Many thanks to the CentOS Project team for their assistance in making this happen!

Categories: Informatika

CentOS Blog: Updated CentOS Vagrant Images Available (v1803.01)

2018, April 10 - 21:08

We are pleased to announce new official Vagrant images of CentOS Linux 6.9 and CentOS Linux 7.4.1708 for x86_64 (based on the sources of RHEL 7.4). All included packages have been updated to 3rd April 2018.

Known Issues
  1. The VirtualBox Guest Additions are not preinstalled; if you need them for shared folders, please install the vagrant-vbguest plugin and add the following line to your Vagrantfile: config.vm.synced_folder ".", "/vagrant", type: "virtualbox"

    We recommend using NFS instead of VirtualBox shared folders if possible; you can also use the vagrant-sshfs plugin, which, unlike NFS, works on all operating systems.

  2. Since the Guest Additions are missing, our images are preconfigured to use rsync for synced folders. Windows users can either use SMB for synced folders, or disable the sync directory by adding the line config.vm.synced_folder ".", "/vagrant", disabled: true

    to their Vagrantfile, to prevent errors on "vagrant up".

  3. Vagrant 1.8.5 is unable to create new CentOS Linux boxes due to Vagrant bug #7610
  4. Vagrant 1.8.7 is unable to download or update boxes due to Vagrant bug #7969.
  5. Vagrant 1.9.1 broke private networking, see Vagrant bug #8166
  6. Vagrant 1.9.3 doesn't work with SMB sync due to Vagrant bug #8404
  7. The vagrant-libvirt plugin is only compatible with Vagrant 1.5 to 1.8
  8. Installing open-vm-tools is not enough for enabling shared folders with Vagrant’s VMware provider. Please follow the detailed instructions in https://github.com/mvermaes/centos-vmware-tools (updated for this release).
  9. Some people reported "could not resolve host" errors when running the centos/7 image for VirtualBox on Windows hosts. Try adding the following line to your Vagrantfile: vb.customize ["modifyvm", :id, "--natdnshostresolver1", "off"]
Recommended Setup on the Host

Our automatic testing is running on a CentOS Linux 7 host, using Vagrant 1.9.4 with vagrant-libvirt and VirtualBox 5.1.20 (without the Guest Additions) as providers. We strongly recommend using the libvirt provider when stability is required.

Downloads

The official images can be downloaded from Vagrant Cloud. We provide images for HyperV, libvirt-kvm, VirtualBox and VMware.

If you never used our images before:

vagrant box add centos/6 # for CentOS Linux 6, or... vagrant box add centos/7 # for CentOS Linux 7

Existing users can upgrade their images:

vagrant box update --box centos/6 vagrant box update --box centos/7 Verifying the integrity of the images

The SHA256 checksums of the images are signed with the CentOS 7 Official Signing Key. First, download and verify the checksum file:

$ curl http://cloud.centos.org/centos/7/vagrant/x86_64/images/sha256sum.txt.asc -o sha256sum.txt.asc $ gpg --verify sha256sum.txt.asc

If the check passed, you can use the corresponding checksum when downloading the image with Vagrant:

$ export box_checksum="4440a10744855ec2819d726074958ad6cff56bb5a616f6a45b0a42d602aa1154" $ vagrant box add --checksum-type sha256 --checksum $box_checksum --provider libvirt --box-version 1803.01 centos/7 Feedback

If you encounter any unexpected issues with the Vagrant images, feel free to ask on the centos-devel mailing list, or via IRC, in #centos on Freenode.

Ackowledgements

We would like to warmly thank Fabian Arrotin and Thomas Oulevey for their work on the build infrastructure, as well as Patrick Lang from Microsoft for testing and feedback on the Hyper-V images.

We would also like to thank the following people (listed alphabetically):

  • Graham Mainwaring, for helping with tests and validations;
  • Michael Vermaes, for testing our official images, as well as for writing the detailed guide to using them with VMware Fusion Pro and VMware Workstation Pro;
  • Kirill Kalachev, for reporting and debugging the host name errors with VirtualBox on Windows hosts.
Categories: Informatika

CentOS Blog: Seven.centos.org is dead .. long life to blog.centos.org !

2018, April 9 - 08:03

When we initially launched seven.centos.org, the idea was just to have a single blog instance that CentOS Dev and QA team members could use to give feedback and also report status update about the rebuild and testing of CentOS 7 : that was an easy entry point for people wanting to know how far we were in the process, what to expect, etc (and so give more transparency that during the CentOS 6 rebuild era) ... That was in 2014.

Then it continued to be used by some contributors who wanted to give hints or talk about CentOS 7 new features, but without having a personal blog (or if their personal blog wasn't aggregated through our http://planet.centos.org instance). As more and more people joined the CentOS SIGs , seven.centos.org was more and more used a central blogging platform around the CentOS ecosystem, and so not really anymore about the status of CentOS 7 itself (which was released in July 2014). We even linked authentication against our (deployed in the mean time) https://accounts.centos.org (through OpenID).

So we thought it was time to rename it to blog.centos.org, to reflect the reality. All previous links/permalinks are still working, but default URL is now blog.centos.org.

Happy blogging !

Categories: Informatika

CentOS Seven blog: CentOS Atomic Host 7.1803 Available for Download

2018, April 6 - 03:34

The CentOS Atomic SIG has released an updated version of CentOS Atomic Host (7.1803), a lean operating system designed to run Linux containers, built from standard CentOS 7 RPMs, and tracking the component versions included in Red Hat Enterprise Linux Atomic Host.

This release rolls up all package minor updates that shipped through the month of March, including, most significantly, a move to docker version 1.13.

CentOS Atomic Host includes these core component versions:

  • atomic-1.22.1-1.gitd36c015.el7.centos.x86_64
  • cloud-init-0.7.9-9.el7.centos.6.x86_64
  • docker-1.13.1-53.git774336d.el7.centos.x86_64
  • etcd-3.2.15-1.el7.x86_64
  • flannel-0.7.1-2.el7.x86_64
  • kernel-3.10.0-693.21.1.el7.x86_64
  • kubernetes-node-1.5.2-0.7.git269f928.el7.x86_64
  • ostree-2017.14-2.el7.x86_64
  • rpm-ostree-client-2017.11-1.atomic.el7.x86_64
Download CentOS Atomic Host

CentOS Atomic Host is available as a VirtualBox or libvirt-formatted Vagrant box, or as an installable ISO, qcow2 or Amazon Machine image. For links to media, see the CentOS wiki.

Upgrading

If you're running a previous version of CentOS Atomic Host, you can upgrade to the current image by running the following command:

# atomic host upgrade Release Cycle

The CentOS Atomic Host image follows the upstream Red Hat Enterprise Linux Atomic Host cadence. After sources are released, they're rebuilt and included in new images. After the images are tested by the SIG and deemed ready, we announce them.

Getting Involved

CentOS Atomic Host is produced by the CentOS Atomic SIG, based on upstream work from Project Atomic. If you'd like to work on testing images, help with packaging, documentation -- join us!

You'll often find us in #atomic and/or #centos-devel if you have questions. You can also join the atomic-devel mailing list if you'd like to discuss the direction of Project Atomic, its components, or have other questions.

Getting Help

If you run into any problems with the images or components, feel free to ask on the centos-devel mailing list.

Have questions about using Atomic? See the atomic mailing list or find us in the #atomic channel on Freenode.

Categories: Informatika

CentOS Seven blog: SuperComputing is #PoweredByCentOS

2018, April 3 - 21:36

Last week I, and one of my colleagues, had the opportunity to attend SuperComputing Asia in Singapore. The great thing about the various SuperComputing conferences is getting to see what amazing things people are doing with HPC (High Performance Computing) to make the world a better place. This was very much the case last week at SC-Asia.

We had the opportunity to interview three people who are using HPC to solve real world problems, and I wanted to share those interviews with you.

First we spoke with Abhishek Saha who is an engineering student at National University of Singapore. He's working with the  Hydroinformatics Institute of Singapore to simulate water run-off across the entire island, to propose solutions for flooding.

Next, we spoke with Nick Zang who is a research fellow at Nanyang Technological University. He's investigating jet engine noise, and ways of reducing that noise:

Finally, we spoke with Yap Jia Qing, who is the Founder & CEO of Nurture.AI, an organization dedicated to encouraging AI researchers to publish their findings in AI along with open source implementations of the research, in order to reduce the burden of reproducing, and then building on, that research. This, in turn, greatly accelerates the progress of AI research.

The first two of these researchers are using CentOS in their their supercomputing infrastrucures, as well as using the large CentOS infrastructure at the National SuperComputing Center. Nurture.ai is an Ubuntu shop. All of the work from all three of these projects is open source, in an effort to accelerate research and implementations.

Categories: Informatika

CentOS Seven blog: CentOS Linux can only come from the CentOS Project

2018, March 26 - 11:00

An open letter from the CentOS Board.

We didn’t think we would have to say this, but here it is:

A rebuild of CentOS Linux is NOT CentOS Linux.

We can’t tell you how good a particular rebuild is, but we can definitely tell you one thing:  if we didn’t build it, it is not CentOS Linux.

The CentOS Project trademark guidelines make it clear that no one has the project’s permission to use the “CentOS” mark for software that is not built and signed by the project.

https://www.centos.org/legal/trademarks/

Unless the binaries are from the CentOS Project, it is not CentOS Linux. It should not be called “CentOS”. Doing so causes confusion with everyone. The only official maintainer of any images is the CentOS Project.

Other groups are welcome to take the CentOS sources, rebuild them, and produce their own modified distribution, as long as they do not call it CentOS or otherwise act without our permission in using the CentOS name. Such distributions are not CentOS, and they should have their own name.

Better yet, we welcome anyone to participate in the CentOS Project and to help us with CentOS Linux. To build something into CentOS Linux you need to be an active part of the community, such as these folks:

If you want your work with open source software to be included via one of the above or a new SIG, here’s where to start:

https://wiki.centos.org/SpecialInterestGroup

The value of CentOS Linux is in the community:  the participants and the users. When you use CentOS Linux you are part of a community full of people helping each other. You are using the platform that underlies so much upstream open source community development. That is the value of the trademark -- it says that you are getting the real software from the real community.

If you are interested in using (real) CentOS Linux in various places, you can find our software here:

https://www.centos.org/download/

Categories: Informatika

CentOS Seven blog: Updated CentOS Vagrant Images Available (v1802.01)

2018, March 10 - 08:55

We are pleased to announce new official Vagrant images of CentOS Linux 6.9 and CentOS Linux 7.4.1708 for x86_64 (based on the sources of RHEL 7.4). All included packages have been updated to 28th February 2018.

Known Issues
  1. The VirtualBox Guest Additions are not preinstalled; if you need them for shared folders, please install the vagrant-vbguest plugin and add the following line to your Vagrantfile: config.vm.synced_folder ".", "/vagrant", type: "virtualbox"

    We recommend using NFS instead of VirtualBox shared folders if possible; you can also use the vagrant-sshfs plugin, which, unlike NFS, works on all operating systems.

  2. Since the Guest Additions are missing, our images are preconfigured to use rsync for synced folders. Windows users can either use SMB for synced folders, or disable the sync directory by adding the line config.vm.synced_folder ".", "/vagrant", disabled: true

    to their Vagrantfile, to prevent errors on "vagrant up".

  3. Vagrant 1.8.5 is unable to create new CentOS Linux boxes due to Vagrant bug #7610
  4. Vagrant 1.8.7 is unable to download or update boxes due to Vagrant bug #7969.
  5. Vagrant 1.9.1 broke private networking, see Vagrant bug #8166
  6. Vagrant 1.9.3 doesn't work with SMB sync due to Vagrant bug #8404
  7. The vagrant-libvirt plugin is only compatible with Vagrant 1.5 to 1.8
  8. Installing open-vm-tools is not enough for enabling shared folders with Vagrant’s VMware provider. Please follow the detailed instructions in https://github.com/mvermaes/centos-vmware-tools (updated for this release).
  9. Some people reported "could not resolve host" errors when running the centos/7 image for VirtualBox on Windows hosts. Try adding the following line to your Vagrantfile: vb.customize ["modifyvm", :id, "--natdnshostresolver1", "off"]
Recommended Setup on the Host

Our automatic testing is running on a CentOS Linux 7 host, using Vagrant 1.9.4 with vagrant-libvirt and VirtualBox 5.1.20 (without the Guest Additions) as providers. We strongly recommend using the libvirt provider when stability is required.

Downloads

The official images can be downloaded from Vagrant Cloud. We provide images for HyperV, libvirt-kvm, VirtualBox and VMware.

If you never used our images before:

vagrant box add centos/6 # for CentOS Linux 6, or... vagrant box add centos/7 # for CentOS Linux 7

Existing users can upgrade their images:

vagrant box update --box centos/6 vagrant box update --box centos/7 Verifying the integrity of the images

The SHA256 checksums of the images are signed with the CentOS 7 Official Signing Key. First, download and verify the checksum file:

$ curl http://cloud.centos.org/centos/7/vagrant/x86_64/images/sha256sum.txt.asc -o sha256sum.txt.asc $ gpg --verify sha256sum.txt.asc

If the check passed, you can use the corresponding checksum when downloading the image with Vagrant:

$ export box_checksum="4440a10744855ec2819d726074958ad6cff56bb5a616f6a45b0a42d602aa1154" $ vagrant box add --checksum-type sha256 --checksum $box_checksum --provider libvirt --box-version 1801.02 centos/7 Feedback

If you encounter any unexpected issues with the Vagrant images, feel free to ask on the centos-devel mailing list, or via IRC, in #centos on Freenode.

Ackowledgements

We would like to warmly thank Fabian Arrotin and Thomas Oulevey for their work on the build infrastructure, as well as Patrick Lang from Microsoft for testing and feedback on the Hyper-V images.

We would also like to thank the following people (listed alphabetically):

  • Graham Mainwaring, for helping with tests and validations;
  • Michael Vermaes, for testing our official images, as well as for writing the detailed guide to using them with VMware Fusion Pro and VMware Workstation Pro;
  • Kirill Kalachev, for reporting and debugging the host name errors with VirtualBox on Windows hosts.
Categories: Informatika

CentOS Seven blog: CentOS Atomic Host 7.1802 Available for Download

2018, March 6 - 23:29

The CentOS Atomic SIG has released an updated version of CentOS Atomic Host (7.1802), a lean operating system designed to run Linux containers, built from standard CentOS 7 RPMs, and tracking the component versions included in Red Hat Enterprise Linux Atomic Host.

This release rolls up all package minor updates that shipped through the month of February, including, most significantly, a newer version of rpm-ostree with support for overriding base packages during package layering operations. (see below for more details)

CentOS Atomic Host includes these core component versions:

  • atomic-1.20.1-9.git436cf5d.el7.centos.x86_64
  • cloud-init-0.7.9-9.el7.centos.2.x86_64
  • docker-1.12.6-71.git3e8e77d.el7.centos.1.x86_64
  • etcd-3.2.11-1.el7.x86_64
  • flannel-0.7.1-2.el7.x86_64
  • kernel-3.10.0-693.17.1.el7.x86_64
  • kubernetes-node-1.5.2-0.7.git269f928.el7.x86_64
  • ostree-2017.14-2.el7.x86_64
  • rpm-ostree-client-2017.11-1.atomic.el7.x86_64
rpm-ostree override

While it's been possible to layer new packages onto the base CentOS Atomic tree for some time now, overriding existing base packages with layered alternatives either wasn't possible or was considered experimental. Version 7.1802 now allows for overriding base packages.

For example, the origin-clients package that includes OpenShift Origin's "oc" tool conflicts with the kubernetes-client package included in the base tree. You can use package layering and overrides to install the openshift-release rpm, remove the conflicting rpms, and install the origin-clients rpm:

# rpm-ostree install centos-release-openshift-origin # rpm-ostree override remove kubernetes-client kubernetes-node -r # rpm-ostree install origin-clients -r # oc cluster up Starting OpenShift using openshift/origin:v3.7.0 ... Pulling image openshift/origin:v3.7.0 ... Download CentOS Atomic Host

CentOS Atomic Host is available as a VirtualBox or libvirt-formatted Vagrant box, or as an installable ISO, qcow2 or Amazon Machine image. For links to media, see the CentOS wiki.

Upgrading

If you're running a previous version of CentOS Atomic Host, you can upgrade to the current image by running the following command:

# atomic host upgrade Release Cycle

The CentOS Atomic Host image follows the upstream Red Hat Enterprise Linux Atomic Host cadence. After sources are released, they're rebuilt and included in new images. After the images are tested by the SIG and deemed ready, we announce them.

Getting Involved

CentOS Atomic Host is produced by the CentOS Atomic SIG, based on upstream work from Project Atomic. If you'd like to work on testing images, help with packaging, documentation -- join us!

The SIG meets every two weeks as part of the Project Atomic community meeting at 16:00 UTC on Monday in the #atomic channel. You'll often find us in #atomic and/or #centos-devel if you have questions. You can also join the atomic-devel mailing list if you'd like to discuss the direction of Project Atomic, its components, or have other questions.

Getting Help

If you run into any problems with the images or components, feel free to ask on the centos-devel mailing list.

Have questions about using Atomic? See the atomic mailing list or find us in the #atomic channel on Freenode.

Categories: Informatika

CentOS Seven blog: Linchpin 1.5 release

2018, February 22 - 21:15

LinchPin is a simple and flexible hybrid cloud orchestration tool. Its intended purpose is managing cloud resources across multiple infrastructures. These resources can be provisioned, decommissioned, and configured all using declarative data and a simple command-line interface.

Linchpin recently release 1.5, and I had an opportunity to talk with Clint Savage earlier this week about Linchpin and what it offers the world.

You can read more about Linchpin at some of the following places:

Docs: http://linchpin.readthedocs.io
IRC: #linchpin on Freenode
Github: https://github.com/CentOS-PaaS-SIG/linchpin
Mailing list: https://www.redhat.com/mailman/listinfo/linchpin

Linchpin is part of the CentOS PaaS SIG, which you can read more about at https://wiki.centos.org/SpecialInterestGroup/PaaS/

Also, Clint wrote this great article last year, which will give you more background: https://opensource.com/article/17/6/linchpin

 

Categories: Informatika

Fabian Arrotin: Using newer PHP stack (built and distributed by CentOS) on CentOS 7

2018, February 20 - 00:00

One thing that one has to like with Entreprise distribution is the same stable api/abi during the distro lifetime. If you have one application that works, you'll know that it will continue to work.

But in parallel, one can't always decide the application to run on that distro, with the built-in components. I was personally faced with this recently, when I was in a need to migrate our Bug Tracker to a new version. Let's so use that example to see how we can use "newer" php pkgs distributed through the distro itself.

The application that we use for https://bugs.centos.org is MantisBT, and by reading their requirements list it was clear than a CentOS 7 default setup would not work : as a reminder the default php pkg for .el7 is 5.4.16 , so not supported anymore by "modern" application[s].

That's where SCLs come to the rescue ! With such "collections", one can install those, without overwriting the base pkgs, and so can even run multiple parallel instances of such "stack", based on configuration.

Let's just start simple with our MantisBT example : forget about the traditional php-* packages (including "php" which provides the mod_php for Apache) : it's up to you to let those installed if you need it, but on my case, I'll default to php 7.1.x for the whole vhost, and also worth knowing that I wanted to integrate php with the default httpd from the distro (to ease the configuration management side, to expect finding the .conf files at $usual_place)

The good news is that those collections are built and so then tested and released through our CentOS Infra, so you don't have to care about anything else ! (kudos to the SCLo SIG ! ). You can see the available collections here

So, how do we proceed ? easy ! First let's add the repository :

yum install centos-release-scl

And from that point, you can just install what you need. For our case, MantisBT needs php, php-xml, php-mbstring, php-gd (for the captcha, if you want to use it), and a DB driver, so php-mysql (if you targets mysql of course). You just have to "translate" that into SCLs pkgs : in our case, php becomes rh-php71 (meta pkg), php-xml becomes rh-php71-php-xml and so on (one remark though, php-mysql became rh-php71-php-mysqlnd !)

So here we go :

yum install httpd rh-php71 rh-php71-php-xml rh-php71-php-mbstring rh-php71-php-gd rh-php71-php-soap rh-php71-php-mysqlnd rh-php71-php-fpm

As said earlier, we'll target the default httpd pkg from the distro , so we just have to "link" php and httpd. Remember that mod_php isn't available anymore, but instead we'll use the php-fpm pkg (see rh-php71-php-fpm) for this (so all requests are sent to that FastCGI Process Manager daemon)

Let's do this :

systemctl enable httpd --now systemctl enable rh-php71-php-fpm --now cat > /etc/httpd/conf.d/php-fpm.conf << EOF AddType text/html .php DirectoryIndex index.php <FilesMatch \.php$> SetHandler "proxy:fcgi://127.0.0.1:9000" </FilesMatch> EOF systemctl restart httpd

And from this point, it's all basic, and application is now using php 7.1.x stack. That's a basic "howto" but you can also run multiple versions in parallel, and also tune php-fpm itself. If you're interested, I'll let you read Remi Collet's blog post about this (Thank you again Remi !)

Hope this helps, as strangely I couldn't easily find a simple howto for this, as "scl enable rh-php71 bash" wouldn't help a lot with httpd (which is probably the most used scenario)

Categories: Informatika

CentOS Seven blog: CentOS Dojo @ FOSDEM: Videos

2018, February 14 - 22:12

For those of you who were unable to attend the CentOS Dojo in Brussels, here are all of the videos from the event.

Subscribe to our YouTube at youtube.com/TheCentOSProject 

KB's "State of CentOS"

Bert Van Vreckem - Basic troubleshooting of network services

Tomas Oulevey - Anaconda addon development

Matthias Runge - Opstools SIG

Haikel Guemar - Metrics with Gnocchi

Colin Charles - Understanding the MySQL database ecosystem

Fabian Arrotin - Content caching

Sean O'Keeffee - Foreman and Katello

Tom Callaway  - Building modern code with devtoolset

Spyros Trigazis - Practical system containers with Atomic

Kris Buytaert - Deplyong your SaaS stack OnPrem

Categories: Informatika

CentOS Seven blog: FOSDEM 2018

2018, February 6 - 21:25

Another FOSDEM is history. I wanted to take a moment to thank all of the people that helped out at the CentOS table at FOSDEM, as well as at the Dojo before FOSDEM.

We had about 75 people in attendance at the Dojo on Friday, with 12 presentations from various speakers. Some of these presentations are already available on YouTube, with the rest coming over the next few days.

Traffic was steady at the CentOS table, from people new to Linux, all the way 15-year CentOS sysadmin veterans. A huge thank you to everyone who dropped by and chatted with us.

If you missed FOSDEM and the Brussels Dojo, there's always other opportunities to meet CentOS people. This year we expect to have another 4 or 5 Dojos around the world, starting in Singapore next month, and moving on to Meyrin (Switzerland), Oak Ridge (USA), and Delhi (India). If you'd like to host a Dojo anywhere in the world, please get in touch with the Centos-Promo mailing list to see how we can help you achieve your goal. We can usually help find speakers, venues, and funding for your event.

Categories: Informatika

CentOS Seven blog: Updated CentOS Vagrant Images Available (v1801.01)

2018, January 20 - 18:27

We are pleased to announce new official Vagrant images of CentOS Linux 6.9 and CentOS Linux 7.4.1708 for x86_64 (based on the sources of RHEL 7.4). All included packages have been updated to 9 January 2017 and include important fixes for the Meltdown and Spectre vulnerabilities affecting modern processors.

Known Issues
  1. The VirtualBox Guest Additions are not preinstalled; if you need them for shared folders, please install the vagrant-vbguest plugin and add the following line to your Vagrantfile: config.vm.synced_folder ".", "/vagrant", type: "virtualbox"

    We recommend using NFS instead of VirtualBox shared folders if possible; you can also use the vagrant-sshfs plugin, which, unlike NFS, works on all operating systems.

  2. Since the Guest Additions are missing, our images are preconfigured to use rsync for synced folders. Windows users can either use SMB for synced folders, or disable the sync directory by adding the line config.vm.synced_folder ".", "/vagrant", disabled: true

    to their Vagrantfile, to prevent errors on "vagrant up".

  3. Vagrant 1.8.5 is unable to create new CentOS Linux boxes due to Vagrant bug #7610
  4. Vagrant 1.8.7 is unable to download or update boxes due to Vagrant bug #7969.
  5. Vagrant 1.9.1 broke private networking, see Vagrant bug #8166
  6. Vagrant 1.9.3 doesn't work with SMB sync due to Vagrant bug #8404
  7. The vagrant-libvirt plugin is only compatible with Vagrant 1.5 to 1.8
  8. Installing open-vm-tools is not enough for enabling shared folders with Vagrant’s VMware provider. Please follow the detailed instructions in https://github.com/mvermaes/centos-vmware-tools (updated for this release).
  9. Some people reported "could not resolve host" errors when running the centos/7 image for VirtualBox on Windows hosts. Try adding the following line to your Vagrantfile: vb.customize ["modifyvm", :id, "--natdnshostresolver1", "off"]
Recommended Setup on the Host

Our automatic testing is running on a CentOS Linux 7 host, using Vagrant 1.9.4 with vagrant-libvirt and VirtualBox 5.1.20 (without the Guest Additions) as providers. We strongly recommend using the libvirt provider when stability is required.

Downloads

The official images can be downloaded from Vagrant Cloud. We provide images for HyperV, libvirt-kvm, VirtualBox and VMware.

If you never used our images before:

vagrant box add centos/6 # for CentOS Linux 6, or... vagrant box add centos/7 # for CentOS Linux 7

Existing users can upgrade their images:

vagrant box update --box centos/6 vagrant box update --box centos/7 Verifying the integrity of the images

The SHA256 checksums of the images are signed with the CentOS 7 Official Signing Key. First, download and verify the checksum file:

$ curl http://cloud.centos.org/centos/7/vagrant/x86_64/images/sha256sum.txt.asc -o sha256sum.txt.asc $ gpg --verify sha256sum.txt.asc

If the check passed, you can use the corresponding checksum when downloading the image with Vagrant:

$ export box_checksum="4440a10744855ec2819d726074958ad6cff56bb5a616f6a45b0a42d602aa1154" $ vagrant box add --checksum-type sha256 --checksum $box_checksum --provider libvirt --box-version 1801.02 centos/7 Feedback

If you encounter any unexpected issues with the Vagrant images, feel free to ask on the centos-devel mailing list, or via IRC, in #centos on Freenode.

Ackowledgements

We would like to warmly thank Fabian Arrotin and Thomas Oulevey for their work on the build infrastructure, as well as Patrick Lang from Microsoft for testing and feedback on the Hyper-V images.

We would also like to thank the following people (listed alphabetically):

  • Graham Mainwaring, for helping with tests and validations;
  • Michael Vermaes, for testing our official images, as well as for writing the detailed guide to using them with VMware Fusion Pro and VMware Workstation Pro;
  • Kirill Kalachev, for reporting and debugging the host name errors with VirtualBox on Windows hosts.

Update : this blog post was updated on January Wednesday 24th to reflect different checksum as the image to use is 1801_02

Categories: Informatika

Fabian Arrotin: Diagnosing nf_conntrack/nf_conntrack_count issues on CentOS mirrorlist nodes

2018, January 19 - 00:00

Yesterday, I got some alerts for some nodes in the CentOS Infra from both our monitoring system, but also confirmed by some folks reporting errors directly in our #centos-devel irc channel on Freenode.

The impacted nodes were the nodes we use for mirrorlist service. For people not knowing what they are used for, here is a quick overview of what happens when you run "yum update" on your CentOS node :

  • yum analyzes the .repo files contained under /etc/yum.repos.d/
  • for CentOS repositories, it knows that it has to use a list of mirrors provided by a server hosted within the centos infra (mirrorlist=http://mirrorlist.centos.org/?release=$releasever&arch=$basearch&repo=updates&infra=$infra )
  • yum then contacts one of the server behind "mirrorlist.centos.org" (we have 4 nodes so far : two in Europe and two in USA, all available over IPv4 and IPv6)
  • mirrorlist checks the src ip and sends back a list of current/up2date mirrors in the country (some GeoIP checks are done)
  • yum then opens connection to those validated mirrors

We monitor the response time for those services, and average response time is usually < 1sec (with some exceptions, mostly due to network latency also for nodes in other continents). But yesterday the values where not only higher, but also even completely missing from our monitoring system, so no data received. Here is a graph from our monitoring/Zabbix server :

So clearly something was happening and time to also find some patterns. Also from our monitoring we discovered that the number of tracked network connections by the kernel was also suddenly higher than usual. In fact, as soon as your node does some state tracking with netfilter (like for example -m state ESTABLISHED,RELATED ), it keeps that in memory. You can easily retrive number of actively tracked connections like this :

cat /proc/sys/net/netfilter/nf_conntrack_count

So it's easy to guess what happens if the max (/proc/sys/net/netfilter/nf_conntrack_max) is reached : kernel drops packets (from dmesg):

nf_conntrack: table full, dropping packet

Depending on the available memory, you can get default values, which can be changed in real-time. Don't forget to also tune then the Hash size (basic rule is nf_conntrack_max / 4) On the mirrorlist nodes, we had default values of 262144 (so yeah, keeping track of that amount of connections in memory), so to get quickly the service in shape :

new_number="524288" echo ${new_number} > /proc/sys/net/netfilter/nf_conntrack_max echo $(( $new_number / 4 )) > /sys/module/nf_conntrack/parameters/hashsize

Other option was also to flush the table (you can do that with conntrack -F , tool from conntrack-tools package) but it's really only a temporary fix, and that will not help you getting the needed info for proper troubleshooting (see below)

Here is the Zabbix graph showing that for some nodes it was higher than default values, but now kernel wasn't dropping packets.

We could then confirm that service was then working fine (not "flapping" anymore).

So one can think that it was the only solution for the problem and stop investigation there. But what is the root cause of this ? What happened that opened so many (unclosed) connections to those mirrorlist nodes ? Let's dive into nf_conntrack table again !

Not only you have the number of tracked connections (through /proc/sys/net/netfilter/nf_conntrack_count) but also the whole details about those. So let's dump that into a file for full analysis and try to find a pattern :

cat /proc/net/nf_conntrack > conntrack.list cat conntrack.list |awk '{print $7}'|sed 's/src=//g'|sort|uniq -c|sort -n -r|head

Here we go : same range of IPs on all our mirrorlist servers having thousands of ESTABLISHED connection. Not going to give you all details about this (goal of this blog post isn't "finger pointing"), but we suddenly identified the issue. So we took contact with network team behind those identified IPs to report that behaviour, still to be tracked, but wondering myself if a Firewall doing NAT wasn't closing tcp connections at all, more to come.

At least mirrorlist response time is now back at usual state :

So you can also let your configuration management now set those parameters through dedicated .conf under /etc/systctl.d/ to ensure that they'll be applied automatically.

Categories: Informatika

CentOS Seven blog: Meltdown and Spectre: The response from CentOS

2018, January 18 - 03:53

As you are no doubt well aware, the Meltdown and Spectre bugs are hardware flaws in Intel and AMD chips, and have been all over the tech news for the last few weeks. If you need to get up to speed on what they’re all about, we recommend this great blog post.

CentOS, meanwhile, has not been idle, and has rolled out new kernels for CentOS 6 and CentOS 7 in response, both of which were announced on January 4th. ISO images were made available on January 8th.

Docker containers were made available on January 9th.

EC2 cloud images typically take a few extra days, and will be announced on the centos-announce mailing list.

On January 17th, Johnny Hughes announced an update to the microcode.dat on CentOS 6. You can read more about that in his tweet, and in this mailing list message.

For more information, and further updated, watch the centos-announce mailing list, and our various social media outlets:

 

Categories: Informatika

CentOS Seven blog: PHP 7.2 for CentOS 7 armhfp

2018, January 15 - 17:22

What happens when you need something that is not readily available, but you can help get it done?
In my case, start harrassing people until you get all the info you need. Enter @arrfab and @remicollet.
Fabian got the builder ready, and contacted Remi who got me to use his SRPMS, all I had to do was push the packages to the builders and wait, and wait, and wait some more....

Status:
The current status is that we have php-7.2.1 working, as you can see in the screenshot, with only basic tests done for the moment, but all successful.
Most of the packages are built, some are being a little stubborn, but we'll get it done. But here is where you come in, we need testing (heavy testing), real user case scenarios.
If you want to see a Spectre of what things are going to be, and you are not afraid your computer may have a complete Meltdown, you can keep reading.

Installing:
Currently we are focused on building only the opt-in php replacement, and all the other platform dependant packages from Remi's repo (noarch rpms are not currently the main target, so you should get it from Remi's repo).
If you don't already have a "test subject", please follow the steps on https://wiki.centos.org/SpecialInterestGroup/AltArch/Arm32 first, including  EPEL, which is done with the following command:

cat > /etc/yum.repos.d/epel.repo << EOF [epel] name=Epel rebuild for armhfp baseurl=https://armv7.dev.centos.org/repodir/epel-pass-1/ enabled=1 gpgcheck=0 EOF

Then all that is left is adding the test repo like this:

cat > /etc/yum.repos.d/php72-testing.repo << EOF [php72-testing] name=Remi php72 rebuild for armhfp baseurl=https://armv7.dev.centos.org/repodir/community-php72-testing/ enabled=1 gpgcheck=0 EOF

As I said before,  we aren't rebuilding noarch packages, so if you need one of those, just add remi's repo like this:

cat > /etc/yum.repos.d/remi.repo << EOF [remi] name=Remi's RPM repository for Enterprise Linux 7 - $basearch mirrorlist=http://cdn.remirepo.net/enterprise/7/remi/mirror enabled=1 gpgcheck=1 gpgkey=https://rpms.remirepo.net/RPM-GPG-KEY-remi EOF

Feedback:
Come find us on the CentOS on ARM-Dev list at https://lists.centos.org/mailman/listinfo/arm-dev

Thanks for testing!!!
Pablo.

Categories: Informatika

Fabian Arrotin: Using a RaspberryPI3 as Unifi AP controller with CentOS 7

2018, January 10 - 00:00

That's something I should have blogged about earlier, but I almost forgot about it, until I read on twitter other people having replaced their home network equipment with Ubnt/Ubiquiti gear so I realized that it was on my to 'TOBLOG' list.

During the winter holidays, the whole family was at home, and also with kids on the WiFi network. Of course I already had a different wlan for them, separated/seggregated from the main one, but plenty of things weren't really working on that crappy device. So it was time to setup something else. I had opportunity to play with some Ubiquiti devices in the past, so finding even an old Unifi UAP model was enough for my needs (just need Access Point, routing/firewall being done on something else).

If you've already played with those tools, you know that you need a controller to setup the devices up , and because it's 'only' a java/mongodb stack, I thought it would be trivial to setup on a low-end device like RaspberryPi3 (not limited to that , so all armhfp boards on which you can run CentOS would work)

After having installed CentOS 7 armhfp minimal on the device, and once logged, I just had to add the mandatory unofficial epel repository for mongodb

cat > /etc/yum.repos.d/epel.repo << EOF [epel] name=Epel rebuild for armhfp baseurl=https://armv7.dev.centos.org/repodir/epel-pass-1/ enabled=1 gpgcheck=0 EOF

After that, just installed what's required to run the application :

yum install mongodb mongodb-server java-1.8.0-openjdk-headless -y

The "interesting" part is that now Ubnt only provides .deb packages , so we just have to download/extract what we need (it's all java code) and start it :

tmp_dir=$(mktemp -d) cd $tmp_dir curl -O http://dl.ubnt.com/unifi/5.6.26/unifi_sysvinit_all.deb ar vx unifi_sysvinit_all.deb tar xvf data.tar.xz mv usr/lib/unifi/ /opt/UniFi cd /opt/UniFi/bin /bin/rm -Rf $tmp_dir ln -s /bin/mongod

You can start it "by hand" but let's create a simple systemd file and use it directly :

cat > /etc/systemd/system/unifi.service << EOF [Unit] Description=UBNT UniFi Controller After=syslog.target network.target [Service] WorkingDirectory=/opt/UniFi ExecStart=/usr/bin/java -jar /opt/UniFi/lib/ace.jar start ExecStop=/usr/bin/java -jar /opt/UniFi/lib/ace.jar stop [Install] WantedBy=multi-user.target EOF systemctl daemon-reload systemctl enable unifi --now

Don't forget that :

  • it's "Java"
  • running on slow armhfp processor

So that will take time to initialize. You can follow progress in /opt/UniFi/logs/server.log and wait for the TLS port to be opened :

while true ; do sleep 1 ; ss -tanp|grep 8443 && break ; done

Dont forget to open the needed ports for firewall and you can then reach the Unifi controller running on your armhfp board.

Categories: Informatika

CentOS Seven blog: CentOS Atomic Host 7.1712 Available for Download

2018, January 9 - 19:05

The CentOS Atomic SIG has released an updated version of CentOS Atomic Host (7.1712), a lean operating system designed to run Linux containers, built from standard CentOS 7 RPMs, and tracking the component versions included in Red Hat Enterprise Linux Atomic Host.

This release includes updated kernel, linux-firmware and microcode_ctl packages to address recent security advisories, alongside other minor updates that shipped during the month of December.

CentOS Atomic Host includes these core component versions:

  • atomic-1.20.1-9.git436cf5d.el7.centos.x86_64
  • cloud-init-0.7.9-9.el7.centos.2.x86_64
  • docker-1.12.6-68.gitec8512b.el7.centos.x86_64
  • etcd-3.2.9-3.el7.x86_64
  • flannel-0.7.1-2.el7.x86_64
  • kernel-3.10.0-693.11.6.el7.x86_64
  • kubernetes-node-1.5.2-0.7.git269f928.el7.x86_64
  • ostree-2017.11-1.el7.x86_64
  • rpm-ostree-client-2017.9-1.atomic.el7.x86_64
Download CentOS Atomic Host

CentOS Atomic Host is available as a VirtualBox or libvirt-formatted Vagrant box, or as an installable ISO, qcow2 or Amazon Machine image. For links to media, see the CentOS wiki.

Upgrading

If you're running a previous version of CentOS Atomic Host, you can upgrade to the current image by running the following command:

# atomic host upgrade Release Cycle

The CentOS Atomic Host image follows the upstream Red Hat Enterprise Linux Atomic Host cadence. After sources are released, they're rebuilt and included in new images. After the images are tested by the SIG and deemed ready, we announce them.

Getting Involved

CentOS Atomic Host is produced by the CentOS Atomic SIG, based on upstream work from Project Atomic. If you'd like to work on testing images, help with packaging, documentation -- join us!

The SIG meets every two weeks as part of the Project Atomic community meeting at 16:00 UTC on Monday in the #atomic channel. You'll often find us in #atomic and/or #centos-devel if you have questions. You can also join the atomic-devel mailing list if you'd like to discuss the direction of Project Atomic, its components, or have other questions.

Getting Help

If you run into any problems with the images or components, feel free to ask on the centos-devel mailing list.

Have questions about using Atomic? See the atomic mailing list or find us in the #atomic channel on Freenode.

Categories: Informatika

Karanbir Singh: turn off unused GPU on the laptop

2018, January 2 - 22:41

Lots of us have dual graphics cards in the laptops these days, but almost everyone I know tends to use one or the other, hardly ever switching on the fly, since typical usage patterns tend to stick for periods of time.

One thing that almost no one seems to do however is turn off the unusued gpu – when on the move, this can have a significant impact on your battery life.

On CentOS Linux 7, the way to do this would be something like this :

echo ‘OFF’ > /sys/kernel/debug/vgaswitcheroo/switch

And thats it, lterally send it the OFF and the unused gpu is powered down.

You can also querry the interface as follows:

# cat /sys/kernel/debug/vgaswitcheroo/switch

On my Thinkpad T460p it looks like this :

0:IGD:+:Pwr:0000:00:02.0
1:DIS: :DynOff:0000:02:00.0

For more info on the vgaswitcheroo, take a look at your kernel document eg https://www.kernel.org/doc/html/v4.10/gpu/vga-switcheroo.html

Enjoy!

Categories: Informatika

Fabian Arrotin: Lightweigth CentOS 7 i686 desktop on older machine

2018, January 2 - 00:00

So, end of the year is always when you have some "time off" and so can work on various projects that were left behind. While searching for other hardware collecting dust in my furniture (other blog post coming soon about that too) I found my old Asus Eeepc 900 and was wondering if I could resurrect it.

While it was working CentOS 5 and then 6 "just fine" I wanted to give it a try with CentOS 7.

Of course, if you remember the specs from that ~2008 small netbook, you remember that it had :

  • slow cpu (Intel(R) Celeron(R) M processor 900MHz)
  • only 1Gb of ram
  • very limited disk space (ASUS-PHISON OB SSD 4GB + additional 8GB for my model)

Setting up the full Gnome3 experience on it would be completely useless and also unusable. So let's try to setup CentOS 7 AltArch minimal (needed as cpu is only i686/32bits) and add what we need after that. So here we go :

  • Download netinstall iso image (I used "local" mirror for me , so http://mirror.nucleus.be/centos-altarch/7/isos/i386/CentOS-7-i386-NetInstall-1611.iso)
  • use dd to transfer it to usb storage key
  • starting the installed on the eeepc
  • wait .... wait .... wait ...

Once installed and up2date, one needs to add additional repositories that aren't there by default. As a reminder, there is no official Epel builds for i686 (same as for armhfp ) but Johnny started to rebuild Epel SRPMs for that specific reason, so here we go :

cat > /etc/yum.repos.d/epel.repo << EOF [epel] name=Epel rebuild for i686 baseurl=https://buildlogs.centos.org/c7-epel/ enabled=1 gpgcheck=0 EOF cat > /etc/yum.repos.d/kernel.repo << EOF [kernel] name=LTS kernel for i686 baseurl=https://buildlogs.centos.org/c7.1708.exp.i386/ enabled=1 gpgcheck=0 EOF

If you see the other kernel repository, that's because the needed ath5k kernel module for the Wifi device in the Eeepc isn't there in the default kernel nor available through elrepo, but it works with that 4.9.x LTS kernel we build and maintain/update for AltArch so let's use it.

We can install what we need (YMMV though) :

yum update -y yum groupinstall -y 'X Window System' yum install -y openbox lightdm lightdm-gtk systemctl enable lightdm.service yum install -y tint2 terminator firefox terminus-fonts-console terminus-fonts network-manager-applet gnome-keyring dejavu-sans-fonts dejavu-fonts-common dejavu-serif-fonts dejavu-sans-mono-fonts open-sans-fonts overpass-fonts liberation-mono-fonts liberation-serif-fonts google-crosextra-caladea-fonts google-crosextra-carlito-fonts echo 'tint2 &' >> /etc/xdg/openbox/autostart echo 'nm-applet &' >> /etc/xdg/openbox/autostart systemctl reboot

The last line with tint2 , terminator and firefox is purely optional but that's what I needed on my eeepc. Same for network-manager-applet, but once installed, it gives you easy to work with applet integrated in openbox environment.

You can then customize it, etc, but I like it so far for what I wanted to use that old netbook for :

Categories: Informatika

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