This problem appears when I try to rsync directories with hosts inside a cluster used NAT for forwarding ports to internal nodes. Hence, the ssh port for internal nodes are not the default 22. So, how to use rsync with the non-standard ssh ports? The -e options of rsync play the trick very well. For…
It was ever possible to set it in gnome-teak-tool. However, in the latest Gnome 3, it disappears. Is there any other way to set it? The configuration is the org.gnome.desktop.wm.preferences titlebar-font under dconf. You can use dconf-editor to find the appropriate key entry and set it. Or use gsettings: $ gsettings set org.gnome.desktop.wm.preferences titlebar-font ‘Sans…
How to install Python environment in my own account on Dreamhost so that my application can use the python that I installed by myself instead of the system-wide one? The post for Bluehost works very well for Dreamhost too: https://my.bluehost.com/cgi/help/python-install In short: mkdir ~/python cd ~/python wget http://www.python.org/ftp/python/2.7.2/Python-2.7.2.tgz tar zxfv Python-2.7.2.tgz find ~/python -type d…
I messed up with one file in one repository and want to check out only that file back to a commit. How to achieve this? To check the file with my_file.name at git commit commit_sha1: $ git checkout commit_sha1 my_file.name You can also use the relative commit instead of commit_sha1 such as master~4, HEAD~4, HEAD^,…
I have access to different git servers. I have several keys for these servers. How to use different keys for different git servers? Use the .ssh/config file to specify different configuration for different SSH servers used by git: For example: Host git.example.org Port 22111 IdentityFile ~/.ssh/id_rsa.git.example.org Host code.example.org Port 22 IdentityFile ~/.ssh/id_rsa.code.example.org which specifies the…
libvirt uses files for VM images by default under /var/lib/libvirt/images/. LVM is a convenient tool for managing VM images. How to use LVM groups with libvirt? This post discusses the method to add LVM groups as a storage pool for libvirt: http://ailoo.net/2011/02/use-a-lvm-volume-group-with-libvirt/ For a general introduction of the storage management in libvirt, please check: http://libvirt.org/storage.html
There are lots internal and external links on my site. Unfortunately, some of them are broken over years. How to find out all these broken links on my site? I use this tool http://www.brokenlinkcheck.com/ which can detect the broken links well. More info here: Broken links checker for sites
Linux supports different timer sources and a machine can have multiple ones. How to find the available Linux timer source and the current one used? Find the current timer source: $ cat /sys/devices/system/clocksource/clocksource0/current_clocksource Find all available timer sources: $ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
My OCaml program prints: Fetal error: Exception “Stack_overflow” without any further information. How to find out which function causes this “Stack_overflow” exception? First, recompile your OCaml program with -g. Second, rerun your OCaml program with OCAMLRUNPARAM=b and the backtrace will be printed out after the “Stack_overflow” exception.
How to install sbt for scala on Fedora Linux? It is not included in the default Fedora repository although scala is included. The download page of scala-sbt.org provides the RPM package. You can install the sbt rpm package by yum. We only need the URL to the RPM package. Here, let take version 0.13.1 as…
How to remove trailing spaces at the end of each line in a file on Linux? Use this script with sed: cat your_file | sed ‘s/[[:blank:]]+$//g’
I have some old emails left in the Evolution local directory (unfortunately not in the mail server’s imap directory). So how to import the Evolution directory which contains some files for the emails to Thunderbird so that I can copy them to the imap directory if needed? You can do this in two steps: First,…
This is the scenario: I want to remove a old hard disk which is a LVM PV and contains data. There is free space available on other PVs in the VG. It should move the data from the disk to be removed to other PVs and then remove the disk. The process to remove sdb…
How to set up auto indenting for OCaml code in Vim? The built-in indenting in Vim for OCaml seems not very good. Please check the post at https://www.systutorials.com/5212/auto-indenting-for-ocaml-code-in-vim-with-ocp-indent/
How to display the network usage by processes like top for CPU/mem on Linux? The nethogs tool is my favorite: nethogs – Net top tool grouping bandwidth per process
How to attach and mount Xen DomU’s disk to Dom0 To attach phy:vg_xen/vm-10.1.1.228 to xvda on Domain-0: # xm block-attach Domain-0 phy:vg_xen/vm-10.1.1.228 xvda w Mount the new partition /dev/xvda2 to /mnt/xvda2: # mount /dev/xvda2 /mnt/xvda2 After finishing using the partition, umount it and detach it: # umount /mnt/xvda2/ # xm block-detach Domain-0 xvda
How to convert an integer into a string of many characters padded with 0s in bash. To do this in C: sprintf(buffer, “%08d”, n); which convert integer n to a 8-character string padded with leading 0s. How to padding a integer with 0s in bash? In bash, you can also use printf For the previous…
How to find the disk space left for a file on Linux? For example, a program may append data to a file: /mnt/logs/app-log.log How to find which partition the app-log.log is on and how much disk space left on that partition? Use this command: $ df -B1 /mnt/logs/app-log.log | tail -1 | cut -d’ ‘…
How to get the output of a system command in C? The system function is handy. But how to get the output? popen is a useful function for this purpose: https://www.systutorials.com/docs/linux/man/3p-popen/ You can use normal file operation functions like fgets to read file content from the file opened by popen.
How to hard reset an Amazon Kindle 5? First, press and hold the power button for 30 seconds. Second, release the power button and wait for the kindle to restart. After a while, the progress bar appear and kindle is rebooting.