Oracle: Unbreak my Linux Heart

Just getting started using Dell's OpenManage Server Administrator (OMSA) on our Oracle Linux platform. There are some confusing instructions going around so it's not immediately clear what to do, hence my blogging here. :) There is a site on Dell - Hardware Monitoring , as well as a wiki with instruction on how to setup their OMSA tooling using yum or up2date. [update]My first update for their instructions: be sure your server has Internet access, as most servers will use a proxy or so. use export http_proxy=http://yourproxy.example.com:port to configure it just for the session, and setup up2date to use an HTTP proxy by editing the settings in /etc/sysconfig/rhn/up2date .

Through an explanation about memory management in Linux on the Gentoo Wiki, I was lead to an article on KernelTrap about High Memory In The Linux Kernel . Though I'm still not sure, this leads me to believe Oracle compiles the kernel with the CONFIG_HIGHMEM4G=y switch on and thus the 3 GB RAM for user space application should be in place. However, I'm forced to test this to make sure. :)

I recently had a question about Linux that created more questions the longer I thought about it. The question was: "Given the app doesn't care, would you recommend 32 bit or 64 bit Oracle Linux for a server?" Driver compatibility plays a part, as does the amount of RAM the app needs. If you need more than 4 GB of RAM, you'll have to use a 64bit kernel... or do you...? I'm still not absolutely sure about it as information is a bit ambiguous. While some say you cannot allocate more than 3.7 GB of RAM to any one process on a 32 bit machine, using PAE , others say to just check free -m or vmstat . Red Hat lists /proc/meminfo as a good source of information and explains what you see there. All said and done, I still don't know for sure. I have a VM with 4 cores and 8 GB of RAM, and it says: [root@server ~]# uname -a Linux server 2.6.9-55.0.0.0.2.ELsmp #1 SMP Wed May 2 14:59:56 PDT 2007 i686 i686 i386 GNU/Linux [root@server ~]# cat /proc/meminfo MemTotal: 805

Red Hat updates Enterprise Linux to version 5.2 . That means Oracle Enterprise Linux and CentOS are soon to follow... Main improvements are "extensive driver updates", enhanced capabilities including power usage, scalability, and manageability (whatever that means) and increased virtualization support (i.e. Xen). [update: improved PAE support]

The sudo mailing list sent a message with instructions for using your Microsoft AD server (aka Domain Controller) as an LDAP host for hosting sudoers. I.e. integrating sudoers in an LDAP server so authentication and authorization on Unix/Linux servers can be managed in a consistent, central way. "Using LDAP to synchronize Users, Groups, Hosts, Mounts, and other commands across an enterprise can greatly reduce the administrative overhead." [from the sudo site ] This way, you extend the AD schema and prepare it for inclusion on your system-wide sudoers file. You then use or switch to an LDAP-enabled sudo version and from then on, access to your *nix hosts can be controlled through LDAP (nothing new there), but also authorization to let certain users use certain commands on certain hosts can be controlled from that same LDAP host. In this particular case, that LDAP host can be your existing Microsoft AD server, which many Unix and Linux administrator have to deal with anyway..

Not we are using this anywhere or in production, but it is useful to know that ext4 file system support is coming soon. Kernel 2.6.24+ adds experimental support already, so you're able to test with it. IBM has a little write up about migrating to ext4 ... which is surprisingly simple!

Just recovered from a boot disk crash... Murphy's Law dictates that the crash happened on our backup server! 6 TB of data potentially useless. Needless to say I'm glad that we managed to recover from it... In the process of recovering, I detected the need to refer to my boot partition in a location independent way. Because my Dell PowerEdge 2950 tends to insert or delete USB partitions and devices "whenever it feels like it", which causes my boot disk to be /dev/sdb1 or /dev/sdc1 or /dev/emcpowere1 , I want to be able to identify it no matter what it is physically called. That's were boot labels come in handy. See the Linux Partition HOWTO on the why and the how. (Note: actually the server inserts/deletes USB device when you add/remove the nousbstorage from the linux kernel boot parameters.

Since we are virtualizing many of our Linux servers, this post was of interest to us: "VMmark 1.0 utilized only 32-bit workloads, which was a reasonable mix when the benchmark was first defined roughly three years ago. However, 64-bit applications and OSes are becoming much more prevalent and we need the ability to characterize this more complex reality. To address this, [ for vmware 1.1 ] we have transitioned three of the VMmark workloads - Java server, database server, and web server - to 64-bit. In order to maintain comparability with the existing version 1.0 results, we have retained the underlying virtual hardware definitions and load levels for each workload." This will let us benchmark our specific ESX host setup and test Oracle Linux VM servers under various settings...