Category: Computer Tips

Sometimes your NFS mount stopped response. You cannot umount normally, if you use umount -l to unmount it, you cannot mount it again, Mounting attempt stalls too. The suggestion on the interenet was to just reboot the client. But you may have important jobs or services on it and you really do not want to. […]

Sometimes when an dnf update was unexpectedly terminated like a power failure, the system may leave an inconsistent rpm database. If this happens, in most case by rebuilding rpm database (rpmdb –rebuilddb), and to use (package-cleanup –cleandupes), it could be fixed. For some severe case, after both, when you are trying to run (dnf update […]

If ForwadX11 and ForwardX11Trusted are both enabled in /etc/ssh/ssh_config, when you do “ssh host” it will invoke X11 forwarding by default. This is convenient when you frequently need to run programs with GUI on remote host. However, with X11 forwarding, if you are simply running a text mode command/script via ssh, like “ssh node ls” […]

echo <your password> | ssh <node name> “sudo -S <command>”

For a RAID NAS box, when the NAS box dies, the data on the drives are still intact. They can be retrieved in the following steps: dd disks containing LVM to hard drive; # create images of hard drives losetup /dev/loopx disks.img; # make images appear as loop devices on OS partx -v -add /dev/loopx; […]

Sometimes a bash script does not run the commands as cron or start up scripts that usually run when you debugging it. This may be caused by that the embedded running environment does not provide proper search path. To avoid this, always use full path to the executibles.

update.packages(checkBuilt=TRUE, ask=FALSE)

The convenient select copy, mouse middle click paste way does not work on some Fedora desktop environment. Even the Ctrl-C/Ctrl-V/Ctrl-X copy past and menu copy-paste does not work, forcing users to hand type in things that usually just a few mouse clicks away. This is identified as a buggy package called “clipit” To identify the […]

Linux search /etc/profile.d and ~/.bashrc, ~/.bash_profile for system and user defined environmental variables. One of the most manipulated variable is $PATH. You can see this by running $ echo $PATH In most cases, when a new 3rd party software is installed, and you want it to be in your default executable search path, you insert […]

For CentOS7, ccmake -DCMAKE_INSTALL_PREFIX=/usr/local/lapack -DCMAKE_BUILD_TYPE=RELEASE -DBUILD_SHARED_LIBS=ON -DLAPACKE=ON .. Then make, make install will get you a working version of liblapacke.so The current version 3.8.0 source has bugs that prevent the .so to work properly. Version 3.7.1 is the best to do. For CentOS8, the Fedora 29 version of Lapack works by dnf install.