Several weeks ago we started seeing some pretty scary errors showing up on the main system disk for our Blackboard server. We had an extra server hanging around, so we decided to move all the data off the failing disk and onto our spare server. The only question was how to make the new server [...]
Below is a list of RHEL system configuration changes that Oracle 10G requires before it is installed.
First, check the following kernel parameters using the commands below:
/sbin/sysctl -a | grep kernel.shmall
/sbin/sysctl -a | grep kernel.shmmax
/sbin/sysctl -a | grep kernel.shmmni
/sbin/sysctl -a | grep kernel.sem
/sbin/sysctl -a | grep fs.file-max
/sbin/sysctl -a | grep net.ipv4.ip_local_port_range
/sbin/sysctl -a | grep net.core.rmem_default
/sbin/sysctl [...]
At least in RHEL 4, the fdisk command does not support the creation of filesystems larger than 2TB. In order to get around it, you have to use the parted command. I found the basic info here, but this is the long and short of how to cut off a big ol’ slice of disk [...]
Unlike other flavors of UNIX, RHEL does not have a command like adduser which walks you through the process step-by-step, so you have to remember the four flags useradd requires, and in what order it expects to receive them. Since I don’t manually add users unless I’m installing a new server, I don’t run the [...]
Since much of my job involves rolling out Linux solutions I’ve been experimenting with VMware Fusion Beta for the Macintosh in my development environment. Given that the product is still in beta, I have very few complaints about its actual stability. Most of the features work reliably as advertised, but there are some basic points [...]
For one reason or another RHEL does not disallow incoming ssh connections as root. This is, of course a glaring security problem which should be addressed for all systems that allow ssh connections to be made from any but the most restricted networks.
The best practice, of course, would be to make the initial ssh connection [...]
So you have a RHEL system and you want to authenticate it against your active directory. The good news is that Red Hat has made it easy for you to do this. The bad news is that they only get the most basic structure working for you. Here I will show you how to get [...]
For some reason that is a complete mystery to me, RHEL does not give you the link status when you run # ifconfig -a. This makes it incredibly hard to debug link integrity issues! Buried amongst all of Red Hat’s proprietary commands, however, is a utility called ethtool, which does give you the status of [...]
The e2fsck will regularly force a check of a filesystem even if the filesystem is marked clean. By default, this happens on every twenty mounts or 180 days, whichever comes first.
The ext3 filesystem does this as well, which can be annoying if you have a very large filesystem and a short downtime window. Therefore, it’s [...]
When many new servers are delivered from the factory, the system clock is way off. Most UNIX systems run “ntpd” to keep the time in sync with internet time servers, which are, in turn synchronized against an atomic clock. This results in a system time that is very very close to the “actual” time of [...]
OpenGroupWare is an open source groupware package intended as an alternative to proprietary applications such as Exchange and PostPath. It is fairly robust in its feature set, and even integrates well with MS Outlook.
Its strongest points, in my opinion are that it does not depend in any way on Active Directory, and that it [...]
Mounting filesystems in RHEL is pretty straightforward and easy. Occasionally, however, you will not want the filesystem to remain mounted all the time, but rather to automatically mount for a set period of time only when it is needed. Because of networking overhead, and the general unreliability of networks, NFS mounts are a good [...]
When you install RHEL, the filesystems are labeled for you. Usually you won't have to mess with it anymore, but on occasion, you may want to change them to more accurately represent the data that is stored on that partition. If, for instance, you used to have all of your database files on a partition [...]
Many system 5 UNIX variants use scripts in the /etc/rcN.d/ directories to control which services should be started in the various runlevels. If, for instance, you wanted the secure shell daemon to run in runlevel 4, you would put a script named something like "S55sshd" in "/etc/rc4.d". This script would usually accept the "start" "stop" [...]
