Linux

My wife has been using Ubuntu rather than Windows Vista, since Ubuntu 8.04 over a year ago.  There were some growing pains in the beginning, but she's pretty happy now.  One of the biggest problems was caused whenever she would play an online game on Pogo, which uses Java, it would basically take over the sound card, not allowing sound from any other application.  The only way to restore sound was to shutdown Firefox, an annoying deal when she had open windows/tabs to many sites.  Until Ubuntu 9.10 I simply changed her shortcuts to run Firefox with the "padsp" wrapper.  This always worked fine, but with Ubuntu 9.10, using "padsp" with Firefox just hangs, either due to a bug in padsp or Firefox or both, I don't know.  I found several bugs filed regarding this problem but no solutions.  Documented here is my solution. Continue reading "Making Sun Java 1.6 play via PulseAudio"

OK, so I've been doing the iSCSI thing for a long time, but recently we had a need to build a RHEL5 VM with access to a legacy Fiber Channel Apple Xserve RAID.  Fortunately our trusty Cisco MDS 9216 w/IP Services Blade can act as an iSCSI to fiber channel gateway, however it does have limits. It only support 3 iSCSI sessions per port, and thus with our 4-port blade we only have 12 total iSCSI-to-FC sessions.  We already use some sessions for iSCSI access to legacy FC tape libraries, so we didn't have enough sessions to connect all of our VMware ESX hosts to both halves of the array (the Xserve is effectively two dumb FC-to-RAID controllers stuffed in a single chassis) and really, only this one host needed access.  Oh yeah, we wanted good performance as well.  Read on for how we did it.
Continue reading "Linux Software iSCSI with Bonding and Multipath"

So, a couple of months ago I wrote about my feelings that Linux will never really be the dominate desktop operating system.  I concluded that this was caused primarily because the developers of Gnome (and to some extent KDE) really don't take into account the average user experience.  They add, change, and break existing functionality on a whim and ship code in known broken state.  In the end this isn't critical to me, I could really care less, I've happily used the Linux desktop for 10 years.  Now though, I'm starting to think that the Linux desktop may even be regressing, and soon even I won't be willing to tolerate this. Continue reading "Is the Gnome Desktop Regressing?"

At work we recently started using BackupPC to do backups of our Linux server.  While the BackupPC website will lead you to believe that it's useful primarily for desktops and laptops, I've found that it's an excellent product for backing up servers as well.  We recently started backing up quite a number of our Linux servers with BackupPC and it works great, however, we did notice one minor problem.  Some of the systems have a large number of files (~4 million) and take many hours to backup (an hour or so even for an incremental).  Based on the order that the files were backed up a backup that started at midnight, where a group of files were modified at 12:45AM might get some of the old files and some of the new ones.  We wanted a consistent image (a backup of the system exactly as it looked when the backup started) and decided that combining BackupPC with an LVM snapshot was the easiest way to achieve this.  Here's what we did. Continue reading "Using BackupPC with LVM Snapshots"

For anyone who knows me the title of this article will be a surprise.  See, I've been running Linux as my desktop OS almost exclusively since 1996.  I had first started with Linux back in 1993 with a very early release of Slackware.  These mainly ran on my old junk machines in my "home lab" and they were fun to hack around with, but really didn't meet my day-to-day needs.  Then, in 1996, I managed to get a copy of Redhat 3.0.3 (Picasso), installed it on my work laptop, and never looked back.  Until about 3 months ago, my laptop ran some variant or another of Redhat (back in 2000 I ran Rehdat variant Yellow Dog Linux on a Mac PowerBook, and in recent years Fedora and/or CentOS).  Sometimes the system was dual-boot with Windows, and I've almost always had a Windows virtual machine lying around (well, at least since 1999 when VMware first came out), but, for 12 years, I haven't owned a computer where anything other than Linux was it's primary OS, and I've spent about 99% of my time in that OS. Continue reading "Linux will never dominate the Desktop"

Here I introduce lvsnap, a simple bash script designed to make creating Linux lvm snapshots easier by allowing snapshots to be defined with a simple configuration file similar to fstab.  It also has support for using bind mounts and can mix and match snapshots and bind mounts to create hierarchies useful as complete chroot environments for backups with tools like rdiff-backup or rsync. Continue reading "Scripting Linux LVM Snapshots"

One of the most annoying aspects of running Linux in VM's on VMware ESX/Server/Workstation is the requirement to reinstall the VMware tools modules after every kernel upgrade.  This is made even more annoying by the fact that the vmware-config-tools.pl script disables network connectivity thus making it difficult to run via remote SSH connections.  A similar problem also affects Linux hosts running VMware Server/Workstation since those products also require running a similar script (vmware-config.pl) to reinstall the required modules after every kernel upgrade on the host OS.

Wouldn't it be nice if the VMware modules just automatically reinstalled themselves when a new kernel was booted, requiring no special attention from the system admin?  Read on for my simple method of accomplishing this. Continue reading "Automating VMware modules reinstall after Linux kernel upgrades"

For the last few weeks I've been fighting a problem with my RHEL5 system running VMware Workstation 5.5.  I'm primarily a Linux user and barely even fire up my Windows XP system, however, every now and then I need Windows for something at work and so I use VMware Workstation 5.5 to run the copy of WIndows XP that came with my Dell laptop.  This has always worked well and I've been doing this for yearsm, however, recently a problem cropped up that was annoying me to no end. Continue reading "VMware Workstation Hangs on RHEL5"

I haven't really been that interested in the projects working to provide eye candy for the Linux desktop.  I couldn't really see the practical application of desktops spinning on a cube or wobbly windows.  However, at a recent meeting of our local LUG (ColaLUG -- stop by if your ever in the Columbia, SC area) one if the attendees mentioned that recent versions of Beryl and Compiz Fusion had features that actually improved desktop productivity.  Things like window zooming, Expose like task switching, etc.  I decided I should give it a spin.

(Updated Mar 20th, 2008) Continue reading "Compiz Fusion on CentOS 5"

At work we have and IBM Bladecenter chassis with several HS20 blades running RHEL4 connected to a EMC Clariion CX700 storage array.  These blades have no internal storage and thus do Boot-from-SAN and obviously have their root volume located on the SAN as well.  Back when these systems were running RHEL3 I had hacked up a mkinitrd based on a Whitepaper from EMC that would include PowerPath within the initial ramdisk so that the root volume was also protected from path failures.  This worked reasonably well for many years but eventually we decided to migrate to RHEL4 and move the systems to dm-multipath.  Unfortunately dm-multipath over root is not supported by RHEL4 (I've been told that this is not an issue in RHEL5 but haven't tested it yet) so I set off to once again "do my own thing".  How hard could it be anyway?

(Updated Sep 22nd, 2007) Continue reading "RHEL4 dm-multipath on root HOWTO"

We recently spent some time troubleshooting some network performance issues with VMware ESX server running on our IBM x336 servers and thought that what we learned might be interesting to others.  Network performance within a VM has always been only so-so, but generally good enough.  With RHEL3/4 VM's on ESX 2.5 we were generally able to get 400-500Mb/s out of a VM using iperf, about half what the physical hardware could do, which I guess isn't too bad.  With ESX 3 we had seen that number rise significantly, with RHEL4 VM's running the vmxnet driver approaching 800-900Mb/s within about 10% of the speed we were seeing on physical hardware.

Unfortunately, this performance increase didn't occur on all hardware platforms, specifically, our IBM HS20 and Dell 1850 servers saw a huge boost in network performance with ESX 3, while our IBM x336 system continue to perform at about 1/3 the speed of the physical hardware.  This really showed up after we switched one of our remote sites from a fiber channel based SAN to an iSCSI solution. Continue reading "Troubleshooting VMware ESX network performance"

At work we use VMware ESX 3 for hosting our servers.  In the US most of our systems are connected to and EMC Clariion array via fiber channel (although we recently purchased an Equallogic PS300E and thus plan to move it to iSCSI in the very near future).  We recently opened a facility in Ireland and were looking to save on the cost of implementing a full SAN.  We needed to host at least 5 servers (possibly a few more within the next year or so), but each server was fairly small.  In the end we purchased two Dell 1850 servers, a Dell/EMC AX150i, and VMware ESX 3.  We knew the performance wouldn't be great, but it seemed good enough for a small site with fairly limited I/O and was a pretty inexpensive way to provide hardware to run 5 servers and have good redundancy.  Unfortunately there have been a few problems with the setup, especially with the RHEL4 guests that we are running.

(Updated June 20th, 2007)

Continue reading "VMware ESX and ext3 journal aborts"

My work laptop was recently upgraded to a Dell D820.  It's a pretty nice system and I've found it to be fairly Linux friendly, however, I ran into several problems getting the wireless to work.  For one thing, the ipw3945 driver isn't yet included in the standard Linux kernel (and may never be due to it's dependence on a binary userspace daemon).  Also, my distro of choice, Fedora Core 5 also doesn't include the driver.  Still, a quick Google search will turn up an abundance of pages that will tell you how to download, compile, and install the ipw3945 driver, however, that didn't quite solve all my problems.

(Updated September 7th, 2006) Continue reading "Using the IPW3945 with Linux, WPA, and the SMP Kernel"

Today I was trying to install a new application on one of our web servers at the office that required PHP5.  Unfortunately that box was running RHEL3 and because of some third-party application certification requirement we really couldn't upgrade it.  Of course I could always just compile and install PHP5 from scratch, but that didn't seem to compelling to me.  Maintaining PHP4 on that box had always been troublesome anyway since one application always required the php-snmp module and Redhat does not officially povide this RPM.  I've always had to download the src RPM, edit the spec file to enable snmp, and build my own php-snmp RPM.  I decided that simply installing PHP5 RPM's might be a solution unfortunately a quick search didn't turn up any prebuilt RPMS for RHEL3. Continue reading "PHP5 on RHEL3"

In my invovlement on various mailing lists the subject of SAN multipath support for RHEL Linux seems to come up on a regular basis.  Until recently there were a multitude of options from various vendors, from failover support in the qla23xx driver, to proprietary modules from EMC, IBM, and HP such as PowerPath, RDAC, and SurePath.  For those people lucky enough to have active/active arrays you could even sometimes use the md multipath feature, however, those of us with active/passive array in many cases had only one fully working option.

With the release of RHEL4 U2-beta that's starting to change as Redhat has included all of the components of the new disk mapper based multipath support and this week I decided to give this new support a spin and see how it works with our EMC Clariion arrays at work.

Continue reading "Testing dm-multipath on RHEL4 U2-beta"