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About using Linux

Missing ports and rpcinfo

I was making an inventory of the bound ports on my server, when I encountered a rather strange situation: a high port that was not associated with any process.

The easiest way to find sockets like that is with:

Lenovo E145: Backlight


The backlight brightness of an Lenovo E145 laptop with a Radeon HD 8240 graphics controller can not be adjusted on Debian. Neither the Fn-F7/Fn-F8 keys are working nor any other interface.


Force the use of the kernel Radeon driver by installing the (non-free) Radeon firmware.


There are several drivers that may be used by the Linux kernel and the X Windows System. The trick is forcing the correct one, as not all drivers support the backlight.

Trouble in libreoffice Calc

I recently started to experience strange behavior in Calc. When I copied cells and pasted them, it sometimes did not work correctly. Worse, when I tried to do a second paste, formulas consistently got lost and I got only the cell values.

It turns out xfce4-clipman is the culprit. This is a plugin that keeps a history of your selections. According to the manual, it is a good idea to check the option Sync selections. Turning it off, though, seems to solve this problem.

Udev: resolve a changed MAC address


After changing the MAC address (Ethernet address) of your network adapter, it does not get an IP address. This can happen within a virtual machine or when replacing the network card in a physical machine. If you try an ifconfig -a or an ip addr list, you see that the name of the network card has changed (for example, from eth0 to eth1).

OpenVPN: Routing content for your connection point


You use a VPN to connect your mobile device, for example your laptop, to your server. All traffic should go through this VPN, as you do not trust random networks you may connect to. This works fine, except when you try to connect to your server through its public IP address. As this is also the IP address that is used as the VPN end point, traffic to it does not go through the VPN but is routed, unencrypted, through the untrusted network.

Sendmail: Using TLS for authentication


You have a laptop or other mobile device running Debian. You have your own Sendmail server, also running Debian. You want to send email from your laptop, but your Sendmail server does not accept your emails if you are not on your local network.

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by Dr. Radut