These are the steps that need to be done when doing an in-place Ubuntu upgrade on a LibreNMS system using do-release-upgrade. Running daily.sh in /opt/librenms should give you most of the errors you need to fix that we will go through in this guide. Most commands here will assume you are running as root or…
Category: Linux
Expand Logical volume in Linux LVM
LVM makes it easy to resize volumes in Linux. This can be done without unmounting drives orrequiring a restart. First determine the free space of the group volume. First determine the partition where your OS is installed. Expand the partition. Here we will assume that the partition is sda3. You can view the volume grow…
Useful Tools
Link Compilation Linux Useful Commands Linux Tool Alternatives
Allow SSH connections only from certain addresses using hosts.deny/hosts.allow
This is the method that can be used to allow SSH connections from certain IP networks. An example use for this is allowing SSH from certain public IP networks, as well as from my Tailscale network. If possible, it is probably better to use iptables/nftables/ufw or the firewall feature of your hosting provider if they…
Rate limit connections in Linux
Use the following iptables command to rate limit connections per IP. This is useful for preventing a DDoS attack on DNS servers. However, for DDoS protection for your DNS servers, you should be hosting DNS with the big cloud providers like Cloudflare, or running dnsdist in front of your authoritive servers.
Enable older SSH key exchange methods
Insert the following in /etc/ssh/ssh_config to apply it system wide or ~/.ssh/config for just your user. It will enable most algorithms that older devices may need. You might get the following error when accessing old SSH servers on Fedora or other RedHat based distributions with weaker keys. To allow these weaker keys, update the crypto…
Yarn Repository Expire Key Error
When using yarn through the apt repo, the key might expire, giving you the following error when updating apt. Issue the following command to update the key and then update the repository.
Create a .pfx/.p12 Certificate File Using OpenSSL
Source: https://www.ssl.com/how-to/create-a-pfx-p12-certificate-file-using-openssl/ The PKCS#12 or PFX format is a binary format for storing the server certificate, any intermediatecertificates, and the private key into a single encryptable file. PFX files are usually found with theextensions .pfx and .p12. PFX files are typically used on Windows and macOS machines to import andexport certificates and private keys. Requirements…
DB_VERSION_MISMATCH error when updating AlmaLinux 8 / RHEL 8 / Rocky Linux
When trying to update the operating system, you might receive an error similar to the following … This can be fixed with the following command to remove the existing database …
Disable the floppy drive module in Linux(Ubuntu)
Sometimes Linux will mistakenly detect a floppy device and create a reference to it because your system does not actually have a floppy drive and you will see errors on the login screen that look similar to blk_update_request: I/O error, dev fd0, sector 0. I find this frequently happens on a VMWare VM. This doesn’t…