Fix for SSH Keys Not Working on Newer Versions of Debian / Ubuntu

If your old SSH keys are not working on newer versions of Ubuntu / Debian, and you're being prompted to login (~/.ssh/config configuration being ignored), the fix is to add the following line to the bottom of the /etc/ssh/ssh_config file:

    PubkeyAcceptedKeyTypes +ssh-rsa

That's it.  It will work again.  You may need to restart the ssh service

sudo service ssh restart

https://askubuntu.com/questions/1404049/ssh-without-password-does-not-work-after-upgrading-from-18-04-to-22-04

Getting Areca Backup to Work on Modern Systems

Unfortunately, Areca Backup hasn't been updated since 2015.  But, it still works great, and it's an awesome program that can compress and encrypt files into a backup archive that can be transferred to a NAS drive or uploaded to the cloud.  However, getting it to work on a modern system can be a chore.  After installing Areca Backup, when you try to launch the application, if nothing happens, you will need to perform both of the following fixes:

Install 32-bit Java first [Windows Offline], and then install 64-bit Java second [Windows Offline (64-bit)] if you have a 64-bit operating system.  Without the 64-bit version of Java, Areca will not launch on a 64-bit system.

The next step to getting Areca to run is to replace the "swt.jar" file in the lib folder found in the installation directory (default is C:\Program Files (x86)\Areca\) with this one:  http://dinofly.com/files/swt.zip

Once the original swt.jar file has been replaced in C:\Program Files (x86)\Areca\lib with the one linked above, Areca will now open and run properly.

Tested on Windows 7 x64, Windows 10 x64, and Windows 11 x64.

Running and Debugging Specific WordPress Cron Hooks Manually Using WP-CLI

If your WordPress instance is configured with debugging turned off (WP_DEBUG set to false in wp-config.php) and you need to troubleshoot, debug, or run a specific WordPress cron hook or function manually, you'll find that it's pretty tough to do so.  Fortunately, I found a relatively easy way to do exactly this using WP-CLI.

Install WP-CLI

Install WP-CLI by using the below commands as root:

sudo -i
curl -O https://raw.githubusercontent.com/wp-cli/builds/gh-pages/phar/wp-cli.phar
chmod +x wp-cli.phar
sudo mv wp-cli.phar /usr/local/bin/wp

Now, change into your WordPress instance vhosts directory:

cd /var/www/vhosts/{YOUR_DOMAIN}/httpdocs

Update the above path as necessary.

To run all the scheduled WordPress cron events, use this command:

wp cron event run --all --allow-root

To run a specific WordPress cron hook, use this command:

wp cron event run "NAME_OF_CRON_HOOK" --allow-root

If you need help determining the name of the cron job hook you specifically want to run or debug, install the WP Control plugin in your WordPress instance. Then visit the /wp-admin/tools.php?page=crontrol_admin_manage_page page to see a list of cron hooks and when they run.  Grab the name from the "Hook" column and update your wp cli command to run that cron event!

You can add echo statements and other code to your individual cron function plugins to better debug and troubleshoot them.

OpenVPN Expired CRL – VPN Won't Connect

Recently, I ran into an issue where OpenVPN was no longer working for existing clients.  After looking at the OpenVPN log in /var/log/openvpn.log, I found the following:

VERIFY ERROR: depth=0, error=CRL has expired:

If you see an OpenVPN error about an expired certificate revocation list (CRL), here's how to generate a new CRL:

cd /etc/openvpn/easy-rsa
EASYRSA_CRL_DAYS=3650 ./easyrsa gen-crl
cp /etc/openvpn/easy-rsa/pki/crl.pem /etc/openvpn/crl.pem
chown nobody:nogroup /etc/openvpn/crl.pem
service openvpn restart

Problem solved!

Support Older TLS Versions in Newer Ubuntu / Debian OS Versions

Edit openssl.conf file:

sudo nano /etc/ssl/openssl.cnf

Add this line at the top:

openssl_conf = openssl_init

And add these lines at the end:

[openssl_init]
ssl_conf = ssl_sect

[ssl_sect]
system_default = system_default_sect

[system_default_sect]
CipherString = DEFAULT@SECLEVEL=1

https://askubuntu.com/questions/1233186/ubuntu-20-04-how-to-set-lower-ssl-security-level#answer-1296578

Ubuntu: Allow Automatic Updates for Specific Packages Only

If you want to allow Google products and packages to update automatically, follow this guide.

You can also add additional sources that should update automatically following the same process.

This is helpful when using Selenium, WebDriver for Chrome, and Python.  Doing this allows you to always use the most up-to-date version of all of these dependent packages.

Tested in Ubuntu 20.04

Setup Remote Logging on an Ubuntu rsyslog Server for DD-WRT to Use

Enable remote logging on an Ubuntu server by configuring rsyslog to allow remote connections from port 514 (adjust as needed):

sudo nano /etc/rsyslog.conf

Uncomment the imudp and imtcp load module statements like so (adjusting as needed):

# provides UDP syslog reception
module(load="imudp")
input(type="imudp" port="514")

# provides TCP syslog reception
module(load="imtcp")
input(type="imtcp" port="514")

Create a logging template and apply it only to remote hosts that start with "c-" (comcast connection remote host prefix [followed by the IP address of the device which can change])

# Comcast remote logging
$template remote-incoming-logs, "/var/log/remote_logs/%HOSTNAME%/%PROGRAMNAME%.$
if $fromhost startswith "c-" then -?remote-incoming-logs

Save and quit.

Restart the rsyslog daemon:

sudo service rsyslog restart

Remote logs will be stored in /var/log/remote_logs

Configure logrotate to process and rotate these logs automatically (so you don't lose them and have a history on them):

sudo nano /etc/logrotate.d/ddwrt

Paste these contents into the file:

/var/log/remote_logs/*.log /var/log/remote_logs/*/*.log {
    daily
    missingok
    compress
    delaycompress
    su syslog adm
}

Save and quit.

Everything has been configured, and remote logging should work from your DD-WRT router once you set the remote URL to your server's IPAddress:port combo and apply the changed settings.

Installing and Configuring CentOS to Host KVM Virtual Machines

GUI

When configuring a fresh install of CentOS for a KVM host machine (the main server that hosts all of the virtual machines), I like to run a GUI to make managing some of the virtual machines easier.  Thus, during install, choose the options for CentOS with Minimal GUI:

RAID 10 LVM Partitions

When configuring the hard drive partitions, set it up to use RAID 10 LVM SOFTWARE RAID:

Create volume group called "vms" without the quotes that is setup as RAID 10 (set volume group space to be as large as possible).

Set the "/" partition to 100GB XFS LVM (RAID10).

Set the "swap" partition to 32GB.

Only setup those two partitions.  The remaining space in the RAID 10 volume group "vms" will be used for KVM containers (and the remaining space does NOT need to be assigned to any mount points).

That's all.

Increasing KVM Guest Hard Disk (Hard Drive) Space

Increasing the hard drive space in a KVM guest can be rather tricky.  The first step is to shutdown (completely turn off) the guest machine by running the below command from the guest system:

sudo shutdown -h now

Once the guest machine has been turned off (verify it is off by using sudo virt-manager on the host machine to see if it's no longer running), on the host machine, resize the LVM partition by running the following command (and adjust the size as necessary):

sudo lvextend -L+78G /dev/vg_vps/utils

If you need help identifying the name of the disk your guest has been assigned, run this command from the host:

sudo virsh domblklist {VIRSH_NAME_OF_VIRTUAL_MACHINE}

For my example, I would use this command:

sudo virsh domblklist utils

From the host machine, download the GParted live ISO image for your system's architecture (x86 or x64).  Start virt-manager:

sudo virt-manager

Assign a CD drive to the virtual machine you're expanding the hard drive space for, and assign / mount the GParted ISO to it.  Change the boot order so that the KVM guest boots from the CD first.  Save your settings and start the KVM guest virtual machine.  Boot into GParted Live.  GParted will run automatically.  Use GParted to expand the partitions so that they make use of the added storage based on your own preferences.  Apply the resize operation.  Exit GParted and shutdown the virtual machine so that it's off again. Remove the CD drive from the boot options from virt-manager, and then start the KVM guest again. 

If Guest Doesn't Use LVM Partitioning

If your KVM guest virtual machine hasn't been configured to use LVM, the added hard drive space should already be available to your system.  Verify it has been expanded by again running the df -h command.  You're done!

If Guest Uses LVM

Let the OS boot.  From the guest, the file system needs to be resized itself.  You can do this by running the following command to see the current space allocated to your system's partitions:

df -h

You'll see a bunch of output similar to:

Filesystem                  Size  Used Avail Use% Mounted on
udev                        2.9G     0  2.9G   0% /dev
tmpfs                       597M  8.3M  589M   2% /run
/dev/mapper/utils--vg-root  127G   24G   98G  20% /
tmpfs                       3.0G     0  3.0G   0% /dev/shm
tmpfs                       5.0M     0  5.0M   0% /run/lock
tmpfs                       3.0G     0  3.0G   0% /sys/fs/cgroup
/dev/vda1                   720M   60M  624M   9% /boot
tmpfs                       597M     0  597M   0% /run/user/1000

You'll notice that the added hard drive space doesn't show up on any of the partitions.  However, it is available to be assigned to these partitions.  To assign additional space, you will need to resize it using these commands (run from the guest virtual machine… the machine you're resizing):

lvextend /dev/mapper/utils--vg-root -L +78G
resize2fs /dev/mapper/utils--vg-root

Obviously, you need to substitute the name of the LVM partition with the one from your system shown in your output of the df -h command.

Resources

https://tldp.org/HOWTO/LVM-HOWTO/extendlv.html – Mirror if Offline

https://sandilands.info/sgordon/increasing-kvm-virtual-machine-disk-using-lvm-ext4 – Mirror if Offline

Obtaining Let's Encrypt HTTP Validation Server IP Addresses

Use your webserver logs:

sudo apt-get install john
cat access_log.1 | grep "Let's Encrypt" | awk '{print $1}' | unique ips
cat ips