Some applications writing files in the /tmp directory can see huge improvements when memory is used instead of disk.
By default in RHEL 7 / CentOS 7, the /tmp directory resides in the logical volume/physical partition associated with /:
# df -k /tmp
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mapper/rhel-root 3030800 1069380 1787752 38% /
Here, another way to check the configuration:
# systemctl is-enabled tmp.mount
To change this behavior and put the /tmp directory into memory, type:
# systemctl enable tmp.mount
Now, if you check the new configuration, this is what you get:
# df -k /tmp
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 508988 8 508980 1% /tmp
Remember not to write big files due to the limited space and, obviously, don’t expect persistence across reboots.
If you don’t know the kpartx command, you miss something!
If you regularly play with virtual machines under KVM, you know that sometimes things go wrong.
A change in the /etc/fstab file or in the ssh configuration and you are in trouble, you can no longer access your virtual machine because you hadn’t set any virtual console: you need to reinstall it and it’s not fun!
But there is a solution! I call it emergency procedure.
This solution consists in stopping your virtual machine with the destroy command, then map your virtual machine image file in your physical host environment with the kpartx command. Mount the /boot partition and edit your /boot/grub2/grub.cfg file, adding the console=ttyS0 string at the end of every kernel boot line.
Finally, unmount the /boot partition, unmap your virtual machine image and reboot your virtual machine: from now on, you’ve got your virtual console!
This tip works at least for RHEL 6/CentOS 6 and RHEL 7/CentOS 7.
To get all the details, go to the RHEL 7 virtual console page.
With Systemd, the Init scripts are not there any more. Consequently, the execution of tasks at boot time had to change.
Hopefully, a nice solution has been found: it uses the good old rc.local file.
Now, to execute tasks at boot time, you put them into the /etc/rc.d/rc.local file.
Then, you change the execution permissions on this file:
# chmod u+x /etc/rc.d/rc.local
Besides allowing executions of tasks, this simple operation activates the new rc-local Systemd service for all the further boots (this is like systemctl enable in Systemd language).
Finally, you can start the rc-local service and, this way, test the execution of the rc.local file:
# systemctl start rc-local
SSD optimization is a good example of such a rc-local service.
Just a reminder for RHCEv5: you’ve got still 29 days to get recertified by passing the RHCEv6 only (a 50% discount is available in some countries).
Today, CentOS 7 has just been released.
The distribution can now be downloaded from the CentOS website.
The Release Notes explain what kind of images are available:
- the DVD images contain most of the packages but not all,
- the Live media images are also stored on DVD and allow you to decide to install the distribution or not with a reduced number of packages,
- the Livecd image, stored on a CD, is a basic distribution,
- the Everything image contains all the available packages.
In addition, the CentOS 7 FAQ gives you some tips:
- How to activate your Ethernet network interface during the installation,
- How to keep the old network interface names,
- How to disable IPv6.
This is a good news for those who want to start to learn RHEL 7 but can’t afford to pay the fee.
Yesterday, there was a live chat organized by Red Hat on Twitter.
The subjects were RHEL 7 training and certifications.
Here is a retranscription:
- RHCSAv6 & RHCEv6 exams are available until December, the 19th but availability varies by location.
- According to location, RHCSAv6 & RHCEv6 can still be taken in exam centers or only in kiosk/onsite.
- A candidate with a current or future RHCSAv6 can become RHCEv7 by passing the RHCEv7 exam only.
- Red Hat recommends taking the RHCE Certification Lab, available as classroom, virtual training, & online, before taking the RHCEv7.
- According to location, a RHCEv5 can get a 50% discount to take both RHCSAv6 et RHCEv6.
- The RHCEv7 changes (4 hours instead of 2, more topics, etc) have been made based on input and guidance of Red Hat Certified Professionals.
- All kiosk exam environments are entirely local (no latency) and keyboards can be remapped if a localized keyboard is not already available.
- Other courses will be updated to RHEL 7 before the end of this year.
- It is still possible to (re)download a certificate/transcript (“Red Hat hereby certifies…”) for a RHCEv5.
- Courses on RHEL 7 have already started in North America.
- UK kiosk is available in Farnborough and a new London location is looked for.
- The opening of a kiosk in Poland is under consideration.
- RHEL 7 training material should be available in French within the Summer.
Today, the RHCSA & RHCE exam objectives for RHEL 7 are finally available.
Concerning the RHCSA exam objectives, there are very limited changes. Details are available in the RHEL7 RHCSA What’s new? section.
Concerning the RHCE exam objectives, changes are more significant. The exam now lasts 4 hours and numerous objectives have been added (and almost none removed). Details are available in the RHEL7 RHCE What’s new? section.
According to Sai Gopalan, VMware product marketing manager, “after July 25, 2014, customers that purchase VMware vSphere Standard, vSphere Enterprise, or vSphere Enterprise+ (either standalone or as part of a suite) will no longer be eligible to a free SLES for VMware offering.”
In a nutshell, the partnership between Suse Linux Enterprise Server and VMware is over.
The details of the press report are available on the VMware vSphere Blog.
Ten days ago, Red Hat released more than 20 short technical videos about some facets of their new product. These videos are available on the Red Hat Enterprise Linux channel on YouTube.
They are also available broken down by topic in the Videos section of the RHEL7 Free available resources on this website.
Search for the “Red Hat” keywords ;).
The content of the three following RHEL 7 courses are already available:
In addition, Allyn Collins from Red Hat gave the following information:
- The RHEL 7 versions of the System Administration III course (RH255), the new Red Hat Certification Lab course (RH300) and the RHCE exam (EX300) will be live on June 30, 2014, allowing RHEL 5 RHCE to re-certify in the 60-day period,
- Recertifying candidates will have 50% off for RHCSA/RHCE courses/exams as previously.
Source: Red Hat services blog.
Finally, according to the RedHatCertified Facebook account (https://www.facebook.com/RedHatCertified), Red Hat will provide the Red Hat Certified Engineer (RHCE) Exam on Red Hat Enterprise Linux 6 through December 2014.