In environments where certificates are manually deployed, reloading TLS certs is often only done annually when the certificate is near expiration. This long lapse in time often means that someone else has inherited the task of renewal, and the original key in use may even be in question. Luckily, openssl provides a way to validate … Linux: openssl to validate whether private key and TLS certificate match
When using a private key on the client to ssh into a remote server with the matching public certificate in ~/.ssh/authorized_keys, a common failure message from the client is: Permission denied (publickey) The most common reasons for this is private key permissions issues (chmod 600), a misconfiguration of authorized_keys, or trying to send the wrong … Linux: ssh-keygen to check whether ssh private key and public cert are keypair
For Ubuntu, there are a couple of ways you can install the linux-headers package matching the kernel version. You can either explicitly specify the version, or use the meta package as shown below. # specify kernel version using subshell sudo apt-get install -y linux-headers-$(uname -r) # OR meta package that auto-matches kernel sudo apt-get install … Ansible: installing linux-headers matching kernel for Ubuntu
The =~ binary operator provides the ability to compare a string to a POSIX extended regular expression in the shell. Take note, the right-hand side regex cannot be surrounded by quotes or it will be treated as a regular string, it cannot contain spaces, and must conform to POSIX regex rules and use character classes … Bash: Using BASH_REMATCH to pull capture groups from a regex
The sed utility is a powerful utility for doing text transformations. In this article, I will provide an example of how to insert a line before and after a match using sed, which is a common task for customizing configuration files. I have also written a related article on setting and replacing values in a … Linux: Using sed to insert lines before or after a match