When you remove a package with the command
yum remove PKG_NAME
yum will remove all other packages that are dependent on the package you are removing.
To remove a package without removing its dependency on Red Hat Linux or RHEL based distributions like CentOS, AlmaLinux, Rocky Linux or Oracle Linux, you can run the command
rpm -e --nodeps PKG_NAME
If you want to keep files, just remove the entry, use
rpm -e --nodeps --justdb PKG_NAME
Back to rpm
Dropbear is a Lightweight SSH server. You can use it as openssh server alternative. Dropbear is particularly useful for embedded type Linux systems, such as wireless routers.
I have used this when I have a problem with openssh server, after an apt upgrade, openssh server stopped working. I installed dropbear and made it run on an alternative port, so I can debug openssh server problem without worrying about disconnecting from the server.
To install dropbear on Ubuntu, run
apt install dropbear
Let’s change SSH port to non default port by editing the file
vi /etc/default/dropbear
Find
DROPBEAR_PORT=22
Replace 22 with your custom port, I will use port 2222
DROPBEAR_PORT=2222
Find
NO_START=1
Replace with
NO_START=0
That completes the basic dropbear ssh configuration.
Let’s restart dropbear service with
systemctl restart dropbear
Verify dropbear is working with command
ss -lntp | grep dropbear
As you can see dropbear is listening on port 2222. You will be able to login to the server using the custom port
ssh -p 2222 user@IP_ADDR
See SSH
To reset the admin password of a nextcloud installed using the snap package, run
sudo nextcloud.occ user:resetpassword USER_NAME_HERE
It will ask for the new password, once you enter the password and confirmed it your nextcloud admin password will be changed.
When trying to resize a disk on Debian 8, I got the following error
root@rescue:~# growpart /dev/nvme0n1 1
-bash: growpart: command not found
root@rescue:~#Fixed by installing cloud-utils package
apt install cloud-utilsOn newer versions of Debian/Ubuntu, you need to install cloud-guest-utils package.
apt install cloud-guest-utilsOn RHEL/AlmaLinux/CentOS, growpart command is provided by the package cloud-utils-growpart to install, run the command:
yum install cloud-utils-growpartTo install .NET on ubuntu 20.04, run the following commands
wget https://packages.microsoft.com/config/ubuntu/20.04/packages-microsoft-prod.deb -O packages-microsoft-prod.deb sudo dpkg -i packages-microsoft-prod.deb rm packages-microsoft-prod.deb sudo apt-get update sudo apt-get install -y apt-transport-https sudo apt-get update
To find all versions of .NET SDK available, run
apt-cache search dotnet-sdk
To install .NET SDK version 6, run
apt install dotnet-sdk-6.0
For .NET SDK 5, run
apt install dotnet-sdk-5.0
For .NET SDK 3.1, run
apt install dotnet-sdk-3.1
For .NET SDK 2.1, run
apt install dotnet-sdk-2.1
Back to dotnet
CyberPanel is a free hosting control panel. To find MySQL root password on CyberPanel server, run
cat /etc/cyberpanel/mysqlPassword
If you want to change MySQL root password on a CyberPanel server, reset MySQL root password as per
Once the MySQL root password is reset, you need to modify the file
/usr/local/CyberCP/CyberCP/settings.py
Add the new password for user root and cyberpanel
Restart CyberPanel service with command
systemctl restart lscpd
See CyberPanel
When updating packages on CentOS 8 server, I got the following error
[root@instance-20220409-2340 ~]# dnf update Failed loading plugin "osmsplugin": No module named 'librepo' CentOS Linux 8 - AppStream 51 B/s | 38 B 00:00 Error: Failed to download metadata for repo 'appstream': Cannot prepare internal mirrorlist: No URLs in mirrorlist [root@instance-20220409-2340 ~]#
This is because CentOS 8 have reached its End of life.
To fix the dnf error, you can change the repository baseurl to vault.centos.org
sed -i -e "s|mirrorlist=|#mirrorlist=|g" /etc/yum.repos.d/CentOS-* sed -i -e "s|#baseurl=http://mirror.centos.org|baseurl=http://vault.centos.org|g" /etc/yum.repos.d/CentOS-*
You may need to convert CentOS 8 to one of the supported Linux distributions.
To convert CentOS 8 to CentOS 8 Stream, run
dnf --disablerepo '*' --enablerepo=extras swap centos-linux-repos centos-stream-repos dnf distro-sync
AlmaLinux is RHEL 8 based (same as CentOS 8) Linux operating system. They provide easy way to convert CentOS 8 server to AlmaLinux.
How to Migrate CentOS 8 to AlmaLinux
Rocky Linux is an open-source enterprise operating system designed to be 100% bug-for-bug compatible with Red Hat Enterprise Linux.
How to Convert CentOS 8 to Rocky Linux
Oracle Linux 8 is free and open source, based on RHEL 8
https://docs.oracle.com/en/learn/switch_centos8_linux8/index.html
RedHat provides Convert2RHEL script to convert CentOS 8 to RHEL 8. RHEL is now FREE for production up to 16 servers.
See CentOS 8
CUDA® is a parallel computing platform and programming model developed by NVIDIA for general computing on graphical processing units (GPUs). With CUDA, developers are able to dramatically speed up computing applications by harnessing the power of GPUs.
We will install NVIDIA CUDA on a Debian 10 server. Run the following commands as user root. If you are logged in with sudo user, you can run the command “sudo su” to become user root.
Add NVIDIA repository
apt install software-properties-common -y add-apt-repository "deb https://developer.download.nvidia.com/compute/cuda/repos/debian10/x86_64/ /" apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/debian10/x86_64/7fa2af80.pub
Enable the contrib repository
add-apt-repository contrib
Update the apt cache
apt-get --allow-releaseinfo-change update
Install cuda
apt-get -y install cuda
To find Nvidia driver version, you can run the command cat /proc/driver/nvidia/version
root@sok-1:~# cat /proc/driver/nvidia/version NVRM version: NVIDIA UNIX x86_64 Kernel Module 470.103.01 Thu Jan 6 12:10:04 UTC 2022 GCC version: gcc version 8.3.0 (Debian 8.3.0-6) root@sok-1:~#
cuda installed in folder /usr/local/cuda-11.4/bin/, to find version, run
root@sok-1:~# /usr/local/cuda-11.4/bin/nvcc -V nvcc: NVIDIA (R) Cuda compiler driver Copyright (c) 2005-2021 NVIDIA Corporation Built on Mon_Oct_11_21:27:02_PDT_2021 Cuda compilation tools, release 11.4, V11.4.152 Build cuda_11.4.r11.4/compiler.30521435_0 root@sok-1:~#
Add the folder to PATH, edit the file
vi ~/.bashrc
Add following
if [ -d "/usr/local/cuda-11.4/bin/" ]; then
export PATH=/usr/local/cuda-11.4/bin${PATH:+:${PATH}}
export LD_LIBRARY_PATH=/usr/local/cuda-11.4/lib64${LD_LIBRARY_PATH:+:${LD_LIBRARY_PATH}}
fi
Save and exit the file. Reload .bashrc with
source ~/.bashrc
You can find more info on NVIDIA driver with the command
nvidia-smi
Allow CloudFlare IP addresses with ipset
To list
ipset list ipset list -n -t ipset list -n ipset list -t
IP sets are a framework inside the Linux kernel, which can be administered by the ipset utility. Depending on the type, an IP set may store IP addresses, networks, (TCP/UDP) port numbers, MAC addresses, interface names or combinations of them in a way, which ensures lightning speed when matching an entry against a set.
To allow all Cloudflare IP addresses, you can use
apt install ipset ipset create cf4 hash:net for x in $(curl https://www.cloudflare.com/ips-v4); do ipset add cf4 $x; done iptables -A INPUT -m set –match-set cf4 src -p tcp -m multiport –dports http,https -j ACCEPT
When installing r1soft kernel module, I got the following error
root@localhost:~# serverbackup-setup --get-module Failed to find headers at `/lib/modules/4.19.0-20-amd64/build`. Get module failed. Falling back to old get-module ... signal: segmentation fault root@localhost:~#
This was on a Debian server with 4.19.0-20-amd64 kernel.
root@localhost:~# uname -a Linux localhost 4.19.0-20-amd64 #1 SMP Debian 4.19.235-1 (2022-03-17) x86_64 GNU/Linux root@localhost:~# uname -r 4.19.0-20-amd64 root@localhost:~#
To fix the error message, install linux-headers package.
apt install linux-headers-4.19.0-20-amd64
See r1soft backup
Webp is a new image format for the web. It can be used on websites for the fast and efficient loading of images. Webp is an open-source image format created by Google and quickly getting adopted by web developers.
If you use Ubuntu or Debain, you can install webp from the official repository with the command
sudo apt-get install webp
To convert an image to webp format, open the terminal and run
cwebp FILE.png -o FILE.webp
If you want to specify the quality of the converted webp image, you can use -q option.
cwebp -q 60 FILE.png -o FILE.webp
Image viewer comes with Ubuntu won’t display webp images. To view webp images, you can open them in the GIMP image editor or drag and drop them in a web browser. Another way is to use the command-line tool that comes with webp package.
vwebp FILE.webp