This blog was in hiatus already shortly after creation, since I worked on different topics. Being back working as part time systems administrator, I’m planning to revitalize the blog as well.
Modern servers come with a basement management controller (BMC), a little extra computer that allows remote console access, provides all kinds of hardware status information and even allows power control (i.e. turning the server on and off). Dell’s implementation is called iDRAC.
IPMI is a commonly used protocol to access this functionality, even over the network.
I remembered using ipmitool over the network to access the iDRAC in the past. The more I was surprised that suddenly it only gave me an error message:
$ ipmitool -H server-mgmt -U root mc info Password: Get Session Challenge command failed Error: Unable to establish LAN session Get Device ID command failed
I found the solution in .pQd’s log:
Apparently recent firmware versions (in 2016) stopped supporting the default protocol and only continued to support the lanplus protocol, which can be selected with the -I lanplus option. I’m not sure, if I saw this documented somewhere, but it seems, that’s what Dell always intended to use. So the proper command is:
ipmitool -H server-mgmt -I lanplus -U root mc info
If you are using OpenIPMI, the proper option is –driver-type=LAN_2_0, so e.g. for reading sensor values you can use:
ipmi-sensors -h server-mgmt -u root -P --driver-type=LAN_2_0
A colleague recently complained that MiKTeX (a LaTeX distribution for Window) runs much lower on his full-featured workstation than on his less powerful
It was not just a minor difference: Compilation took several minutes on the Workstation, but only a few seconds on the laptop.
The only difference that we found was the way that MiKTeX was installed. When he ran the installer on the workstation, he thought that there would be enough space to make a full install with all included packages. On the laptop the space was rather limited, so he chose a standard install.
Apparently the full package database is processed every time, the compilation process is started. So installing a smaller number of packages not only reduced the necessary space, but also massively improved the runtime.
I recently needed to enable quotas on a larger XFS file system. This is quite easy, because everything you have to do is setting the proper mount options and then mount the file system again. XFS will automatically index all files and update all quota associations while mounting:
But: Depending on how full the file system is, this update process may take a long time. This means, you should not try this while booting because modern Linux distributions (like RHEL7) will have a timeout detection and may thus interrupt the process.
So when enabling quota on an existing file system:
- edit fstab
- unmount the file system
- mount it again
- wait for the quota log update to finish