red hat enterprise linux

Disable GUIs and X Windows on Linux VMs

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This is post #2 in my December-long series on Linux VM performance tuning, Tuningmas. I remember an old story about people having performance issues on their Windows servers. It would happen intermittently, and never when the system administrator was around. Turns out it was the pretty OpenGL screensaver, which would kick in and slow everything down tremendously. When the admin was around he’d be using the console of the server, so no screen saver, and no problems. Graphical user interfaces make one-off administration tasks easier in some cases, but for virtual environments they come at a cost: additional RAM and CPU overhead. For a virtual environment you should shut them off, or install as little of them as you need, …

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Align Your Partitions

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This is post #1 in my December-long series on Linux VM performance tuning, Tuningmas. I wrote about it back in 2006, and lots of others have written about it since (Duncan Epping has a nice vendor-agnostic post with diagrams): misaligned storage trashing your I/O performance. What’s the big deal? In short, it is killing your I/O performance. Logical Block Addressing on your disk drive makes the Master Boot Record 63 bytes long. This means it occupies sectors 0-62 on disk, and the first partition will start at sector 63. The number 63 is a persona non grata in the computer world. It isn’t a power of 2, and it certainly doesn’t line up with your storage’s idea of the world …

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Why Does My Linux VM's Virtual NIC Show Up As eth1?

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Got a Red Hat Enterprise Linux (or CentOS, or Scientific Linux, or Oracle Enterprise Linux, etc.) 6 VM that won’t bring up it’s single network interface after you clone it? Get the following error when you try using /sbin/ifup to enable it? “Device eth0 does not seem to be present, delaying initialization.” When you use “/sbin/ifconfig -a” you see eth1 where eth0 should be? eth1      Link encap:Ethernet  HWaddr 00:50:56:9B:00:85             BROADCAST MULTICAST  MTU:1500  Metric:1           RX packets:812 errors:0 dropped:0 overruns:0 frame:0           TX packets:214 errors:0 dropped:0 overruns:0 carrier:0           collisions:0 txqueuelen:1000           RX bytes:72509 (70.8 KiB)  TX bytes:28324 (27.6 KiB) lo        Link encap:Local Loopback            inet addr:127.0.0.1  Mask:255.0.0.0           inet6 addr: ::1/128 Scope:Host           UP LOOPBACK RUNNING  MTU:16436  Metric:1           …

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Why I Don't Use Third-Party Binary Packages

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There are a number of third-party package repositories out there for Linux distributions. For example, Fedora runs the Extra Packages for Enterprise Linux (EPEL) repository, which contains builds of open source software that isn’t supplied with Fedora or Red Hat Enterprise Linux. Similarly, a lot of projects have their own repositories that supply builds of software for OpenSUSE, Debian, Ubuntu, etc. Maybe it’s just because I’m old-school, and maybe it’s because I enjoy compiling things, but I really don’t like the idea of using binaries found on the Internet. I never have. As an aside, I really tried hard to make the rest of this post not be critical, or seem like criticism, but instead just be a reflection of …

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Strange Characters in My WordPress Blog

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In late August I moved my blog from a host running Red Hat Enterprise Linux 4 to a host running Red Hat Enterprise Linux 6. With it came an upgrade to MySQL, from 4 to 5. The migration itself seemed pretty painless, as I was able to recompile Apache on the new host and just copy everything over intact. I moved the databases by dumping each one and importing them on the other side. A week ago I was doing some work on the blog and noticed that for every apostrophe there were three other characters now: ’. I use a lot of apostrophes, and it sort of sucks to have every “it’s” become “it’s”. More specifically, it was only …

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How to Change SCSI Controllers on your Linux VM

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A question from Matt Vogt prompted this, where he wants to go from the BusLogic  SCSI controller to the LSI Logic SAS controller. It’s actually a straightforward conversion if you have the right steps. This is based on Red Hat Enterprise Linux 3, 4, and 5, but the principle should be the same for everything. It’s basically: snapshot, change config files, change hardware. Red Hat Enterprise Linux 6, in contrast, appears to have all the LSI Logic, parallel & SAS, drivers, as well as the paravirtual SCSI drivers, so all you need to do is shut the VM down and change the type of SCSI controller you’re using. I always recommend trying this on a test VM before you try …

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