Too many content sets for certificate Red Hat Enterprise Linux, Standard (up to 2 sockets) 3 year. A newer client may be available to address this problem.

If your encounter Too many content sets for certificate Red Hat Enterprise Linux, Standard (up to 2 sockets) 3 year. A newer client may be available to address this problem when you are using RHEL 6.3 and below.

Step 1: you need to be able to do a yum install. To be able to do that, at the command prompt, register with RHN Classics

# rhn_register

Step 2: Update Yum subscription

# yum update subscription-manager

Step 3:Subscribe to the Subscription Pool

# subscription-manager subscribe --pool=xxxxxxxxxxxxxxxxxxxxxx

Not loading "rhnplugin" plugin, as it is disabled

After subscribing to the Red Hat Subscription by doing a

# subscription-manager register

After that I did a

# yum clean all
# yum repolist -v
..... 
Not loading "rhnplugin" plugin, as it is disabled
.....

Finally, I did a

# subscription-manager list --available

Select the right pool

# subscription-manager subscribe --pool=xxxxxxxxxxxxxxxxxxxxxx

If it still does not work, go for the RHN Classic

# rhn_register

You can check whether it works by

# yum -d10 repolist

Repo-id      : rhel-x86_64-server-6
Repo-name    : Red Hat Enterprise Linux Server (v. 6 for 64-bit x86_64)
Repo-updated : Tue Nov 10 21:10:32 2015
Repo-pkgs    : 16,298
Repo-size    : 28 G
Repo-baseurl : https://xmlrpc.rhn.redhat.com/XMLRPC/GET-REQ/rhel-x86_64-server-6
Repo-expire  : 21,600 second(s) (last: Thu Nov 12 09:19:23 2015)
Repo-exclude : ibutils-libs*
Repo-excluded: 12

Leap Second on 30th June 2015 and effects on CentOS and RHEL

At 11:59 p.m. on June 30, clocks will count up all the way to 60 seconds. That will allow the Earth's spin to catch up with atomic time.

Background - http://www.usatoday.com/story/tech/2015/01/08/computer-chaos-feares/21433363/

All of Red Hat Enterprise Linux 4, 5, 6 & 7 will be affected.

*Resolve Leap Second Issues in Red Hat Enterprise Linux
https://access.redhat.com/articles/15145

*Are we susceptible to a leap second event?
https://access.redhat.com/articles/199563

*Labs: Leap Second Issue Detector
https://access.redhat.com/labs/leapsecond/

Finding Performance bottlenecks in your application

This is an interesting blog How to find performance bottlenecks in your application by using gperftools and KCachegrind to profile performance bottlenecks.

Do take a look and happy reading.

Red Hat Enterprise Linux 7 is now available

Do read Red Hat Website Announcing the General Availability of Red Hat Enterprise Linux 7!

Key Red Hat Enterprise Linux 7 features include:

• Lightweight, portable Docker containers run applications at near bare-metal speed providing isolation and leveraging SELinux for increased security.
  
• Improved filesystem enhancements including a default XFS filesystem that supports up to 500TB, improvements to NFS 4 adding extended attributes with SELinux labels, and LVM supporting whole volume snapshots with rollback.
  
• Improved interoprability with Microsoft Active Directory domains, allowing Red Hat Enterprise Linux clients to integrate more easily within heterogeneous datacenters.
  
• Centralized management of processes, services, security, and other resources using systemd allowing enhanced, granular control of your system.
  
• Performance tool utilities such as TUNA, Thermostat, and Performance Co-Pilot to allow you to monitor, measure, and resolve application problems.
  
• New management tools like OpenLMI help to create uniformity and standardized administration across systems by managing storage, network, and high-availability resources.
  
• Refined control over system subscriptions allows you to set support priority, audit systems reliably, and see how you're using your subscriptions at a glance.

For more information, do read

• Red Hat Enterprise Linux 7 is here: new improvements to downloads, product page, and doucmentation

Brocade Drivers updates for IBM PureFlex and Blade Centre

Brocade CNA/HBA FC device driver vbfa-3.2.3.0 for RHEL 6 - IBM System x, BladCenter and Flex Systems

The newer models of PureFlex Nodes x240 on-board 10G is from Brocade. If you are using RHEL 6.4/CentOS 6.4, you may want to update the OS with latest Broadcom drivers

Version 3.2.3.0
New Features and Feature Enhancement:

• Support for patching firmware via boot image
• Support for Linux PTP
• Support for UEFI Health Check Protocol
• Support for SLES11SP3
  

Version 3.2.1.1

• Fixes and Enhancements:
• Firmware update to address the thermal notification issue

Encountering eth0 NIC SerDES Link is Down

I was noticing this error on my HS22 Blade log files occasionally and on one occasion the NFS which was relying on the ethernet connection got disconnected and hang when the load is exceedingly high. The problem is that it is very hard to reproduce the problem as it is quite random

My Server is using the Broadcom chipset bnx2 and my version of my CentOS is 5.4 or kernel  version is 2.6.18-164.el5

After a bit of searching, this particular Red Hat Bugzilla (https://bugzilla.redhat.com/show_bug.cgi?id=520888) reflects the problem and workaround very well. I encourage you to take a closer look. If you are not planning to upgrade your RHEL or CentOS to 5.6 ( http://rhn.redhat.com/errata/RHSA-2011-0017.html ) and above yet, you may want to consider the workaround as mentioned in the bugzilla



 From Comments 14

"Configuring IRQ SMP affinity has no effect on some devices that use message signalled interrupts (MSI) with no MSI per-vector masking capability. Examples of such devices include Broadcom NetXtreme Ethernet devices that use the bnx2 driver. 

If you need to configure IRQ affinity for such a device, disable MSI by creating a file in /etc/modprobe.d/ containing the following line: 

options bnx2 disable_msi=1 

Alternatively, you can disable MSI completely using the kernel boot parameter pci=nomsi. (BZ#432451)

" http://www.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/5.4/html/Technical_Notes/Known_Issues-kernel.html

To Check whether you are still having issues, you can use the command

# dmesg |grep bnx2

I guess the best way is to update your broadcom drivers. For latest update on this "NIC SerDES Link is Down", see my writeup on Upgrading of Broadcom Drivers to resolve eth0 NIC SerDES Link is Down

Outline of File Hierarchy Systems in RHEL, CentOS and SL

The location of the files and directories in RHEL or its clone system are based on the Filesystem Hierarchy System (FHS) guidelines. For more information on the Filesystem Hierarchy System (FHS), do read the Filesystem Hierarchy Standard

1. /bin/ (Essential Commands for admins and users)
2. /usr/bin/ (Common commands for admins and users)
3. /sbin/ (Essential commands for admins)
4. /usr/sbin (Common commands for admins)
5. /tmp/ (Temporary files for all users)
6. /usr/local/ (Location for locally-installed software indepndent of operating systems updates)
7. /usr/share/man (Manual Pages)
8. /usr/src (source code)
9. /var/ (variable files such as spool and log files)
10. /var/log/ (Log files)
11. /etc/ (Configuration files)
12. /proc/ (Kernel virtual file system)
13. /dev/ (Device file)

Much of these information is derived from  "Red Hat Enteprise Linux Administration Unleased"

Install Graphviz on CentOS and Fedora

Graphviz is open source graph visualization software.

Graph visualization is a way of representing structural information as diagrams of abstract graphs and networks. Automatic graph drawing has many important applications in software engineering, database and web design, networking, and in visual interfaces for many other domains.

To install GraphViz, download the correct repository according to the distribution of your choice. The supported distribution is Fedora, RHEL, Ubuntu, Windows, Mac

The easiest way to install and maintain graphviz on RHEL or Centos is to use yum. To set up yum, download the graphviz-rhel.repo file

To install  Graphviz,

# yum install graphviz*

Dstat a versatile resource statistics tool

Taken from DAG

Dstat is a versatile replacement for vmstat, iostat, netstat, nfsstat and ifstat. Dstat overcomes some of their limitations and adds some extra features, more counters and flexibility. Dstat is handy for monitoring systems during performance tuning tests, benchmarks or troubleshooting.

Dstat allows you to view all of your system resources instantly, you can eg. compare disk usage in combination with interrupts from your IDE controller, or compare the network bandwidth numbers directly with the disk throughput (in the same interval).

Some of the features includes:

• Combines vmstat, iostat, ifstat, netstat information and more
• Shows stats in exactly the same timeframe
• Enable/order counters as they make most sense during analysis/troubleshooting
• Modular design
• Written in python so easily extendable for the task at hand
• Easy to extend, add your own counters (please contribute those)
• Includes about 10 external plugins to show how easy it is to add counters
• Can summarize grouped block/network devices and give total numbers
• Can show interrupts per device
• Very accurate timeframes, no timeshifts when system is stressed
• Shows exact units and limits conversion mistakes
• Indicate different units with different colors
• Show intermediate results when delay > 1
• Allows to export CSV output, which can be imported in Gnumeric and Excel to make graphs

Make sure you have rpmforge repository installed.

# yum install dstat

Some of the useful commands are as followed:

# dstat --help 

# dstat --full 

# dstat --vmstat 

# dstat --mem 

# dstat --load

Turn off checking for signature during yum localinstall

yum localinstall is a wonderful utility where I can download and install an rpm package and let yum resolve all the dependencies issues for me. Occasionally, during installation, if I don't want to do a signature check. I can use this commands with a --nogpgcheck flag

# yum localinstall gummi-0.4.2-1.noarch.rpm --nogpgcheck

And it work wonderfully

Article on Red Hat Cloud Developments

A good article of Red Hat Cloud Developments. You can download some of the conference presentation slides from the Redhat Summit there as well.

Installing Presto Plugin for yum to boost speed

You can install the Presto Plugin for yum to download the changes from previous download which will reduce download time

# yum install yum-presto

Making yum use the fastest mirror

To make sure yum plugin download packages from the fastest mirror, you can install the following plugins

# yum install yum-fastestmirror

Subversion Error - svn: Could not use external editor to fetch log messages

When I was installing Subversion on CentOS 5.3 x86_64 and when I tried to do a "svn commit". The error was

"svn: Could not use external editor to fetch log message; consider putting the $SVN_EDITOR environment variable or using the --message......."
"svn: None of the environment variables SVN_EDITOR, VISUAL or EDITOR is set..............."


To solve the issue
You have to input the environment variables in your .bash_profile in your home directory
# vim .bash_profile
--------------------------------------
export SVN_EDITOR=/usr/bin/vim
--------------------------------------
# source .bash_profile

Xinetd daemon on CentOS

In the older version of CentOS or Fedora, xinetd daemon was usually installed by default. However, it seems ( I may be wrong) that from CentOS 5, this is not the case. So if you noticed your xinetd daemon is NOT present in your /etc/inet.d but the xinetd.d directory are present. Just run the usual

# yum install xinetd

And it is ready for your use.

Scons - Open Source Construction Tool

SCons is an Open Source software construction tool—that is, a next-generation build tool. Think of SCons as an improved, cross-platform substitute for the classic Make utility with integrated functionality similar to autoconf/automake and compiler caches such as ccache. In short, SCons is an easier, more reliable and faster way to build software.

It has support for Windows and Linux. In particular, for the RHEL distribution, it has the rpm. However, it will need python > 1.5.2. But the user guide recommend Python 2.5 and above

Thoughts on users-install software

Read an interesting FAQ writeup on user-installed software found on Linux Format Aug 09. I thought I summarise the article in my own words.

I think as most system administration will encounter this scenario quite frequently especially in a academic environment that users wants to install software of their own. How do we cope with this?

Suggestion 1: Building from Source
I think one of the easiest method is to simply allow users to install from source file. The users can unpack the source and configure, make and make install. For example:

$ ./configure --prefix=$HOME
$ make
$ make install

(which will install directories like bin, lib and share to the user's home directory)


Suggestion 2: If using RPM, you can use some prefix
$ rpm --prefix=/home/user/local --otheroptions
(and adding an entry to sudoers with sudo)

However, there are some issues as many packages are NOT relocatable and have to be installed to the path that was given when they are compiled.


Suggestion 3: Allowing restricted sudo access
If you allow users to install onto system directories, you can give them restricted rights like installing without removing.

lshw - Listing hardware specification on CentOS

ishw is a small but useful tool to help you list the hardware of your linux box. Alternatively you can use dmidecode to list hardware too. For more information, you can read blog entry dmidecode - Finding hardware details remotely

To install lshw on CentOS, first ensure you have RPMForge Repository installed. For more information on RPMForge, you can take a look at blog entry Installing RPMForge

Step 1: Install lshw

# yum install lshw

Step 2: Install the gui version of lshw

# yum install lshw-gui

Step 3: To have a quick look of your hardware specification

# lshw -short

Step 4: To view specific hardware, you have to use the class option

# lshw -class memory

(For more information on what class, you can find it from lshw -short)

Step 5: To launch the gui version of lshw

# lshw-gui

Notes:

1. lshw Project Page

Singular Application

SINGULAR is a Computer Algebra System for polynomial computations with special emphasis on the needs of commutative algebra, algebraic geometry, and singularity theory.

# wget http://www.mathematik.uni-kl.de/%7emschulze/repo/RPMS/Singular-release.rpm
# rpm -Uvh Singular-release.rpm
# yum install Singular-icons Singular-help

For more information on the application, see http://www.singular.uni-kl.de/