Detect and read DIMM memory module info in linux

 sudo dmidecode -t memory

Update firmware in Debian

To install available firmware updates in Debian, do the following:

sudo apt install fwupd

sudo fwupdmgr refresh

sudo fwupdmgr get-upgrades

sudo fwupdmgr update

Install Linux kernel headers in Debian

sudo apt install linux-headers-$(uname -r) 

Speed-up XRDP on Debian

Edit /etc/xrdp/xrdp.ini

Locate tcp_send_buffer_bytes and change to:

tcp_send_buffer_bytes=4194304

sudo sysctl -w net.core.wmem_max=8388608

Create /etc/sysctl.d/xrdp.conf file and add the following:

net.core.wmem_max = 8388608

Check for SMART status on Debian

 Install smartmontools and use smartctl:

sudo smartctl --all /dev/xxx

Change service shutdown timeout in Debian

Make a change so that slow-non/responding services to terminate quickly during shutdown:

sudo nano /etc/systemd/system.conf

Uncomment and edit to:

DefaultTimeoutStopSec=5s

Reboot or reload with:

sudo systemctl daemon-reload

Change GRUB boot delay

sudo nano /etc/default/grub

sudo update-grub

Adding ufw rules using application profiles while restricting source network

Unfortunately, the ufw help doesn't provide an example for using application profiles while specifying the source network. Here's an example how "OpenSSH" profile can be used but restricting the source network to local:

sudo ufw allow from 192.168.0.0/24 to any app OpenSSH

Disable IPv6 in Debian Trixie

Edit /etc/hosts and remove the default IPv6 entries, including localhost, etc. If you don't do this, you may encounter weird errors down the road because some programs will try to bind to "localhost" and it ends up try using non-existing IPv6 address, etc.

Create the follow file:

sudo nano /etc/sysctl.d/90-disable_ipv6.conf

then add these lines and save:

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

Run:

sudo sysctl --system

Jumbo frame size setting in Windows

For network adapter drivers that require the "Jumbo Packet" value to be set for MTU, enter 9014. This is to accommodate 14 bytes of Ethernet header, which is then added to the 9000-byte packet. For example, Mellanox ConnectX-3 adapters require this value to function correctly.

To confirm testing of Jumbo frame between two nodes, use the ping command as follows:

For Windows:

ping <target> -f -l 8972

For Linux:

ping <target> -M do -s 8972

Upgrade to Debian 13 (trixie)

sudo apt update

sudo apt upgrade

sudo sed -i 's/bookworm/trixie/g' /etc/apt/sources.list

sudo apt update

sudo apt upgrade

sudo reboot

Switching Debian boot mode between text and GUI

To boot into text mode:

sudo systemctl set-default multi-user.target

or to boot into GUI mode:

sudo systemctl set-default graphical.target

Reboot the system

Disable IPv6 on Debian

Append the following in the /etc/sysctl.conf file:




net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1
net.ipv6.conf.tun0.disable_ipv6 = 1

and run:

sudo sysctl -p

and reboot

How to fix “Authentication is required to create a color profile/managed device” when using xrdp

For those folks getting that annoying message when RDP into a Linux host running xrdp.

Create a new config file here:

$sudo nano /etc/polkit-1/localauthority/50-local.d/45-allow-colord.pkla

and put:

[Allow Colord all Users]
Identity=unix-user:*
Action=org.freedesktop.color-manager.create-device;org.freedesktop.color-manager.create-profile;org.freedesktop.color-manager.delete-device;org.freedesktop.color-manager.delete-profile;org.freedesktop.color-manager.modify-device;org.freedesktop.color-manager.modify-profile
ResultAny=no
ResultInactive=no
ResultActive=yes

Credit: https://devanswe.rs/how-to-fix-authentication-is-required-to-create-a-color-profile-managed-device-on-ubuntu-20-04-20-10/