About this website

This website is a collection of my notes when I switched Fedora Core to Ubuntu Linux since 2009. It describes practical knowledge that achieving administration tasks for Ubuntu servers.

Mixing RAID across disks, pros and cons

Many array, 2 disks on RAID 1, and rest on RAID 6. The full system is physically separated from the user data. One can expand user data partition without touching the operating system. Also it is easy to keep a spare system disk and save it off-site.

For servers with limited number of slots, one can mix RAID 1 (/boot) with RAID 6 (other partitions). This gives maximum disk redudency protection with available disk slots.

What RAID for swap?

Migrate RAID


Shrink and expand RAID partition


Replace a failed disk


Build a software RAID array


Software RAID


Fix Error "GConf Error: Failed to contact configuration server; ..."

This error occurs when I run eog and gedit from remote ssh to a Ubuntu server. The problem doesn't exist if I switch to root.

A "just works" solution is to run "rm -rf  .dbus/session-bus/*"


Install MPICH1.2.7p1 with Intel compilers


MPICH2 on the cluster runs a global mpd as root. The initial tests include bash scripts, cpi, some user made programs all passed. But one user program almost always disrupt mpd on slave nodes and prematurely exits. This user program was reported running fine on other cluster with MPICH 1.

So MPICH 1.2.7p1 will be installed on to the cluster to see if mpd was causing trouble for whatever reasons (load, compatibility ...)



Remote command through ssh hangs?

One day I found a script hangs in the middle when it was executed as a remote command through ssh. I log on to that node and run the same script without any problem.  There was nothing special except a background command in the script. Let's just look at this script:



sleep 20 &
echo done

You get message "done" and the shell immediately after issue the command test1.sh directly on the node, but it hangs for 20 seconds if submiited as "ssh localhost test1.sh".

However, this script


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