≡ Menu


BIND 9 Dynamic Update DoS Security Update

BIND 9 is an implementation of the Domain Name System (DNS) protocols. named daemon is an Internet Domain Name Server for UNIX like operating systems. Dynamic update messages may be used to update records in a master zone on a nameserver. When named receives a specially crafted dynamic update message an internal assertion check is triggered which causes named to exit. An attacker which can send DNS requests to a nameserver can cause it to exit, thus creating a Denial of Service situation. configuring named to ignore dynamic updates is NOT sufficient to protect it from this vulnerability. This exploit is public. Please upgrade immediately.
[click to continue…]

Oracle To Purchase Sun Microsystems for $7.4b

Look like combined company will give a tough time to both IBM and HP.

Sun Microsystems and Oracle Corporation announced yesterday that they have entered into a definitive agreement under which Oracle will acquire Sun common stock for a total of $7.4 billion or $5.6 billion net of Sun's cash and debt.
[click to continue…]

Top 10 Linux Virtualization Software

Virtualization is the latest buzz word. You may wonder computers are getting cheaper every day, why should I care and why should I use virtualization? Virtualization is a broad term that refers to the abstraction of computer resources such as:

  1. Platform Virtualization
  2. Resource Virtualization
  3. Storage Virtualization
  4. Network Virtualization
  5. Desktop Virtualization

This article describes why you need virtualization and list commonly used FOSS and proprietary Linux virtualization software.
[click to continue…]

Linux and other Unix-like operating systems use the term "swap" to describe both the act of moving memory pages between RAM and disk, and the region of a disk the pages are stored on. It is common to use a whole partition of a hard disk for swapping. However, with the 2.6 Linux kernel, swap files are just as fast as swap partitions. Now, many admins (both Windows and Linux/UNIX) follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. Let us say I've 32GB RAM, should I set swap space to 64 GB? Is 64 GB of swap space really required? How big should your Linux / UNIX swap space be?

Old dumb memory managers

I think the '2x swap space' rule came from Old Solaris and Windows admins. Also, earlier memory mangers were very badly designed. There were not very smart. Today, we have very smart and intelligent memory manager for both Linux and UNIX.

Nonsense rule: Twice the size of your main system RAM for Servers

According to OpenBSD FAQ:

Many people follow an old rule of thumb that your swap partition should be twice the size of your main system RAM. This rule is nonsense. On a modern system, that's a LOT of swap, most people prefer that their systems never swap. You don't want your system to ever run out of RAM+swap, but you usually would rather have enough RAM in the system so it doesn't need to swap.

Select right size for your setup

Here is my rule for normal server (Web / Mail etc):

  1. Swap space == Equal RAM size (if RAM < 2GB)
  2. Swap space == 2GB size (if RAM > 2GB)

My friend who is a true Oracle GURU recommends something as follows for heavy duty Oracle server with fast storage such as RAID 10:

  1. Swap space == Equal RAM size (if RAM < 8GB)
  2. Swap space == 0.50 times the size of RAM (if RAM > 8GB)

Red Hat Recommendation

Red hat recommends setting as follows for RHEL 5:

The reality is the amount of swap space a system needs is not really a function of the amount of RAM it has but rather the memory workload that is running on that system. A Red Hat Enterprise Linux 5 system will run just fine with no swap space at all as long as the sum of anonymous memory and system V shared memory is less than about 3/4 the amount of RAM. In this case the system will simply lock the anonymous and system V shared memory into RAM and use the remaining RAM for caching file system data so when memory is exhausted the kernel only reclaims pagecache memory.

Considering that 1) At installation time when configuring the swap space there is no easy way to predetermine the memory a workload will require, and 2) The more RAM a system has the less swap space it typically needs, a better swap space

  1. Systems with 4GB of ram or less require a minimum of 2GB of swap space
  2. Systems with 4GB to 16GB of ram require a minimum of 4GB of swap space
  3. Systems with 16GB to 64GB of ram require a minimum of 8GB of swap space
  4. Systems with 64GB to 256GB of ram require a minimum of 16GB of swap space

Swap will just keep running servers...

Swap space will just keep operation running for a while on heavy duty servers by swapping process. You can always find out swap space utilization using any one of the following command:
cat /proc/swaps
swapon -s
free -m

See how to find out disk I/O and related information under Linux. In the end, you need to add more RAM, adjust software (like controlling Apache workers or using lighttpd web server to save RAM) or use some sort of load balancing.

Also, refer Linux kernel documentation for /proc/sys/vm/swappiness. With this you can fine tune swap space.

A note about Desktop and Laptop

If you are going to suspend to disk, then you need swap space more than actual RAM. For example, my laptop has 1GB RAM and swap is setup to 2GB. This only applies to Laptop or desktop but not to servers.

Kernel hackers need more swap space

If you are a kernel hacker (debugging and fixing kernel issues) and generating core dumps, you need twice the RAM swap space.


If Linux kernel is going to use more than 2GiB swap space at a time, all users will feel the heat. Either, you get more RAM (recommend) and move to faster storage to improve disk I/O. There are no rules, each setup and configuration is unique. Adjust values as per your requirements. Select amount of swap that is right for you.

What do you think? Please add your thoughts about 'swap space' in the comments below.

Download 64 Bit Linux Flash Player Beta Version

Finally, Adobe has released 64 bit preview version of its most popular flash player today for Linux / Solaris UNIX operating system. There is no Windows or Mac 64 bit version exists but Linux / UNIX is the first OS to get it. Indeed a good news; now we have both Java and Flash plyaer for 64 bit platforms. No need to use nspluginwrapper. From the blog post:

Furthering Adobe's commitment to the Linux community and as part of ongoing efforts to ensure the cross-platform compatibility of Flash Player, an alpha version of 64-bit Adobe Flash Player 10 for Linux operating systems was released on 11/17/2008 and is available for download. This offers easier, native installation on 64-bit Linux distributions and removes the need for 32-bit emulation. Learn more by reading the 64-bit Flash Player 10 FAQ.

It is being made available for developers and consumers to test their content to ensure new features function as expected, existing content plays back correctly, and there are no compatibility issues.

Please note that you need 64 bit Linux operating system and 64 bit Firefox version to use this new 64 bit player.

Is The Linux Community Afraid of Opensolaris?

It's about time someone wrote this article:

I know the headline is a little bit provoking. But when you think about some comments from Linux proponents you could think so.

This is an interesting development. In the years before, there wasn't such comments. Solaris was considered as a dead end. But then the game changed. We open-sourced Solaris. The full monty over the time. We open-sourced the cluster framework. And we won´t stop to open source further code until there is no more code to open-source. BTW: I find "Sun should contribute more" really interesting. In the moment you start up your text processor on your favourite Linux distribution you've gone through more code contributed by Sun than of anybody else. You´ve already traversed a large amount of code contributed by Sun when you just login into GNOME. This is a fact most people tend to ignore.

Is the Linux community afraid of Opensolaris? [c0t0d0s0.eu]

Sun Solaris on its Deathbed – Claims Jim Zemlin

Jim Zemlin is executive director of the Linux Foundation claims Solaris UNIX is irrelevant and Linux is future. From the article:

Linux is enjoying growth, with a contingent of devotees too large to be called a cult following at this point. Solaris, meanwhile, has thrived as a longstanding, primary Unix platform geared to enterprises.

Sun officials believe the 16-year-old Solaris platform remains a pivotal, innovative platform. But at the Linux Foundation, there is a no-conciliatory stance; the attitude there is to tell Solaris and Sun to move out of the way. "The future is Linux and Microsoft Windows," says foundation Executive Director Jim Zemlin. "It is not Unix or Solaris."

Is Sun Solaris on its deathbed?

Sure Linux has great value but Solaris has its own market share. They make great OS with good features such as DTrace, ZFS and many more. Many government and defense project selects Solaris for Database and many mission critical applications, while Linux used for Web, mail and proxy services.

What do you think?