Error sending Server Messages with Exim4 in Debian

Debian has been installing Exim4 as the default MTA since at least Debian Stretch. When I tried to use it to send service messages (specifically fail2ban ban reports including whois information) on a new bookworm server, the messages would bounce with an Exim “message has lines too long for transport” error. Most modern MUAs like […]

Access a device on another subnet connected to your current network

Use a Raspberry Pi to change default IP Addresses on newly installed devices in a remote Control Panel We have many control systems out in the field connected to our office using IPSEC VPNs. Each control system needs its own subnet (usually a 192.168.x.x/24) to make this work. So, a problem arises if a new […]

Adding Non-Free Drivers to a Debian Installation

When you install a new version of Debian from scratch, you may need “non-free” drivers for things like a Wireless Network Adapter. If these drivers are not GPL-licensed, then Debian will not include them in the installation image. You can work around this by installing the non-free image from a location such as http://cdimage.debian.org/cdimage/unofficial/non-free/cd-including-firmware/10.7.0+nonfree/amd64/iso-cd/ for […]

Exclude Packages from apt-get upgrade

If you need to prevent a package from upgrading during ‘apt-get upgrade’, you need to put that package on hold: $ sudo apt-mark hold package_name When you run ‘apt-get upgrade’ with a package on hold, the output will look like this: $ sudo apt-get upgrade Reading package lists… Done Building dependency tree Reading state information… […]

How To Find The Largest Top 10 Files and Directories On a Linux System

The du (i.e., disk usage) command reports the sizes of directory trees inclusive of all of their contents and the sizes of individual files: -h, –human-readable print sizes in human readable format (e.g., 1K 234M 2G) -s, –summarize display only a total for each argument -x, –one-file-system skip directories on different file systems The sort […]