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Sunday, August 26, 2018

dasung monitor

Dasung monitor: http://www.dasungtech.com

It is a good e-ink monitor. It can connect with my laptop through HDMI. It doesn't have any built-in lights like Kindle Paperwhite or Kindle Oasis. That's a problem which can be solved by using a lamp to beam the light onto the screen. With the right angle, it gives me the same feeling as when I use Kindle. The font size is also a problem. The default font size of my Debian + Awesome WM is too small on a Dasung monitor. I have to manually increase the font size of several programs when I use it, but it's okay. The other sad thing is that the refresh rate is still slow, so you have to be patient. There is no problem with text-based programs, which is what I use most. There is also an issue about the ghosting. I can bear with it. I use the Dasung monitor as my primary monitor for a year or so already. It's perfect for my eyes. I wish the new model of Dasung will be better.

Pro tips

With e-ink monitor which doesn't have color yet, you should set all your programs to have the white background color and black foreground color as much as you can. For websites, e.g., pantip.com, which use a dark background, you can change their styles using Stylish, a Firefox add-on, as you can see from an example here: https://github.com/pchaitat/stylish-pantip-dasung-paperlike-pro

Saturday, June 3, 2017

How To Update VirtualBox

Environment: Debian 8 (64-bit) host, Windows 7 (64-bit) guest

$ sudo apt-get update
$ sudo apt-get upgrade
$ vboxmanage list extpacks
if the version is older than on virtualbox.org, download the new one
$ sudo vboxmanage extpack install --replace <extension_pack_filename>
$ vboxmanage storageattach <vbox_guest_uuid> --storagectl "IDE" --port 0 --device 0 --type dvddrive --medium /usr/share/virtualbox/VBoxGuestAdditions.iso
install VBoxGuestAdditions from Windows 7 (64-bit) guest
$ vboxmanage storageattach <vbox_guest_uuid> --storagectl "IDE" --port 0 --device 0 --type dvddrive --medium emptydrive

Environment: Debian 8 (64-bit) host, Debian 9 (64-bit) guest

in host:

$ sudo apt-get update
$ sudo apt-get upgrade
$ vboxmanage list extpacks
if the version is older than on virtualbox.org, download the new one
$ sudo vboxmanage extpack install --replace <extension_pack_filename>
$ vboxmanage storageattach <vbox_guest_uuid> --storagectl "IDE" --port 0 --device 0 --type dvddrive --medium /usr/share/virtualbox/VBoxGuestAdditions.iso

in guest:

$ sudo apt-get install build-essential module-assistant
$ sudo m-a prepare
$ sudo mount -o exec /dev/cdrom /media/cdrom
$ sudo /media/cdrom/VBoxLinuxAdditions.run
$ sudo umount /media/cdrom

in host:

$ vboxmanage storageattach <vbox_guest_uuid> --storagectl "IDE" --port 0 --device 0 --type dvddrive --medium emptydrive

Sunday, April 30, 2017

Pasting from X selection with keyboard

My mouse's middle button has a problem after I have been using it for a few years. It doesn't easily work when I click it to paste anymore. I have to try clicking the button a few times each time and that is very sad, and it even hurts my hand already. It's time to paste with keyboard instead.

I learn from Google Search that "shift+ins" works. I have tried that with Ubuntu 14.04 (Unity) and Debian (lxde). It works, but not for all cases. Now, I am using a workaround below instead:

xsel | xclip -selection c

It passes the text I select to clipboard and then I can use ctrl+v to paste instead. The bad thing is that it trashes whatever is stored in the clipboard (ctrl+c). But it is reliable. Feel free to map it with other tools at your convenience.

Thursday, March 30, 2017

Windows PowerShell

Running Remote Command with Windows PowerShell inside WORKGROUP

on each machine:

run powershell as admin
Enable-PSRemoting
Set-Item wsman:\localhost\client\trustedhosts *
Restart-Service WinRM

frequently used commands:

Get-Service winrm
Stop-Computer -Force
Enter-PSSession -ComputerName <ip_addr> -Credential <username>
Exit-PSSession
Invoke-Command -ComputerName <ip_addr> Stop-Computer -Force
Set-ExecutionPolicy remotesigned : To run unsigned PowerShell script

Sunday, February 19, 2017

An Example of How To Auto Update System Time in Auto Resumed Guest OS after host OS boots up in KVM

Environments

Host OS: Debian 8
Guest OS: Debian 8

Currently, when we suspend a guest OS for N minutes and resume it, the system time in the guest OS is N minutes in the past.

I configure my KVM system such that when the host OS shuts down or reboots, all the running guest OSes are suspended. And they are automatically resumed after the host OS boots up. (Here is the link which shows you how to do that. Read the section, "Automatic guest management on host shutdown/startup".)

Assuming the host OS and the guest OS are always accessible from the local network, I decide to use SSH and /etc/rc.local to automate the updating of system time of the guest OS after it is automatically resumed.

Here are the steps it takes to do it:

Create a special unix user on the guest OS and, probably, name it, kvmupdatetimeman.
Grant sudo permission to user kvmupdatetimeman by adding the line below in the vi editor which shows up when you issue the command `sudo VISUAL=vi visudo`:
Assuming a unix user on the host OS you want to use for this purpose is debian, set up SSH public key authentication for user debian on the host OS so that it can SSH to the guest OS under user kvmupdatetimeman without having to enter a password. Make sure you SSH from the host OS to the guest OS at least once so that you already have accepted the SSH host key of the guest OS or else our automated script will have problem as we won't handle the accepting of the SSH host key from our script.
On the host OS, add this line to the file /etc/rc.local which is executed every time after the machine boots up.
Add the code below into the file updatesystimeinguest and don't forget to chmod +x it. Assuming the 2 IP addresses in the code are your guest OSes' IP addresses in your local network:

Now, every time you boot up your host OS after shutting down or rebooting, your auto suspended guest OSes which are automatically resumed will have correct system time automatically.

Related links