nixCraft - Linux and Unix tutorials for new and seasoned sysadmin

How to install KVM on Ubuntu 20.04 LTS Headless Server

last updated August 10, 2020 in Linux KVM, Ubuntu Linux, Virtualization

Kernel-based Virtual Machine (KVM) is a virtualization module for the Linux kernel that turns it into a hypervisor. How can I install KVM with bridged networking, set up a guest operating system as the back-end virtualization technology for non-graphic Ubuntu Linux 20.04 LTS server over ssh based session?

Ubuntu 20.04 add network bridge (br0) with nmcli command

last updated August 9, 2020 in Linux, Networking, Ubuntu Linux

How do I configure my Ubuntu 20.4 LTS and add network bridge (br0) with the nmcli command? How can I create a Linux network bridge on Ubuntu Linux 20.04 LTS server for KVM (Kernel-based Virtual Machine)?

Squid test config file for syntax errors

last updated August 8, 2020 in Linux, Squid, UNIX

I installed Squid Proxy server on Ubuntu 20.04 LTS. How do I make sure my squid.conf file is free from syntax errors and test config file for errors?

How to install a Wireguard VPN client in a FreeBSD jail

last updated August 8, 2020 in FreeBSD, FreeBSD Jails (VPS), UNIX

I installed/set up a Wireguard VPN server on Debian 10 Linux box. How do I install, configure and set up a Wireguard client in a FreeBSD jail?

apt-get hold back packages on Ubuntu / Debian Linux

last updated August 6, 2020 in Debian / Ubuntu, Linux, Package Management

How do I hold back packages on an Ubuntu / Debian Linux to prevent updating of a specific package? How can I blacklist package updates using the apt command/apt-get command?

Route 53 Let’s Encrypt wildcard certificate with acme.sh

last updated August 3, 2020 in Amazon Cloud Computing, Apache, Cryptography, Linux, Nginx, UNIX

How do I get a wildcard TLS/SSL certificate from Let’s Encrypt using acme.sh and AWS Route53? How can I set up wildcard Let’s Encrypt SSL with AWS Route53 for Nginx or Apache?

ERROR: Test failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1091)

last updated July 25, 2020 in Amazon Cloud Computing, Cryptography, FreeBSD, FreeBSD Jails (VPS), Troubleshooting, UNIX

When I install s3cmd package on my FreeBSD system and try to use the s3cmd command I get the following error:
ERROR: Test failed: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1091)
How do I fix this problem on FreeBSD Unix system?