This post shows how to use parallel processing to get a CPU intensive job done faster in Unix/Linux. By splitting a large task into several parts, it is quite easy to give each part to a separate CPU, and complete the task many times faster than it would on a single processor.
These days, even small PCs and other devices often come equipped with several CPU cores. But some tasks will use only one core, sometimes using 100% of it, while other cores stand by idle. Sometimes this is a waste of resources. Continue reading →
How to find the memory on a Solaris system hosting primary and guest LDOMs
For capacity planning, it is useful to know how much free resource is available on a given LDOM server. That is, a “parent” system hosting several guest LDOMs. For example, if you want to know how many more LDOM’s the server could support. Continue reading →
If the root password for a Unix system is lost or forgotten, it can be very difficult to regain root access and perform further administration work. Often it will be impossible. You could be lucky – there might be a user account with sudo access, or even a root shell still open on the system somewhere, for example on the system console. If the system is x86, you might be able to boot it from a live CD and restore root access by doctoring the root disk. Otherwise, with most systems (physical and virtual), it will often be a case of rebuilding the system from scratch.
Solaris is a bit different. It has long been possible with Solaris to regain root access by booting the physical system from a Solaris installation CD, mounting the original root disk and removing the root password string from the relevant file, usually /etc/shadow. The same technique works, surprisingly, with SPARC virtual systems, aka LDOMs. Proceed as follows. Continue reading →
An LPAR, or logical partition, is an IBM virtual machine. LPARs run on a variety of IMB hardware and provide strong isolation between partitions. This article describes a method for quickly building LPARs running AIX on IBM pSeries hardware
AIX can be installed onto an LAPR using the distribution CDs (or rather, since this is a virtual machine, the ISO image files derived from those physical CDs). There are, however, two drawbacks with this:
it does not include site specific customizations. If a piece of software like Apache or ssh is required on the LPAR, it must be installed separately – a pain if you have many LPARs to build.
it is a slow process. AIX is supplied spread over several CDs. The administrator must swap CDs several times during the installation. This means hanging around and typing commands needed to mount and dismount the cd ISO images on the target LPAR, something that will have to be done several times during the installation.
The other day I upgraded the memory in a customer’s Linux system from 2 to 8 Gb. Afterwards though, only 4 Gb was “visible”. The “free” and “top” commands confirmed that only half the expected memory was there. The system was running 32 bit Red Hat 4.7 in a vmware virtual machine. Continue reading →
This post is about cloning HP-UX virtual machines, or HPVMs.
Once you have built an HPVM, the hpvmclone command can be used to produce many more. hpvmclone does not create a copy of the HPVM, it just creates a copy of the configuration. The data copy is done manually, for example with the dd command.