Element for Linux Client – Without Flatpak

If you'd like to install the Element Matrix client for Linux without using flatpak or snap, you can use the following script to do so:

sudo apt-get install wget unzip
wget -N "https://dinofly.com/files/linux/element_bash_install.zip" && unzip element_bash_install.zip && sudo bash install_element.sh

This will install the Element client application on Linux, create an app shortcut for it, and add it as an automatic startup program when the computer is first started.

This was tested on Ubuntu 18.04, but it should work on newer versions of Linux as well.

Latest Skype for Debian / Ubuntu – Without Flatpak or Snap

I found this script posted on Github that essentially unpacks the last created Skype .deb file released by Microsoft, downloads the latest snap package for Skype, extracts and replaces the Skype binary from the snap package to the deb source files, replaces some version number strings, and then repacks the files into a deb you can install on Ubuntu / Debian.  I modified the script slightly to install some dependencies and then actually install the deb file that is generated for you.

To install the latest version of Skype for Ubuntu / Debian (tested on Ubuntu 18.04 – and should work on newer versions), first uninstall any previous version of Skype you've installed on your system, and then run the following script:

sudo apt-get install wget unzip
wget -N "https://dinofly.com/files/linux/skype_for_linux_deb_install.zip" && unzip skype_for_linux_deb_install.zip && sudo bash skype_for_linux.sh

If after logging in for the first time, your Skype looks like this (a blank page with it not doing anything):

Restart your computer and load Skype again.  It will work fine after this.

Testing Simultaneous HTTP Requests in Parallel using cURL

If you're developing a web application and are worried that a similar HTTP request could come in multiple times from different users (or clients) exactly at the same time, you can see how your application will behave by using cURL (on modern versions of Linux) to create this rare (if almost impossible) circumstance:

curl --parallel --parallel-immediate --parallel-max 3 --header "Content-Type: application/json" --request POST --data '{STRINGIFIED_JSON_PAYLOAD}' --config urls.txt

The urls.txt file will contain the URL to your API endpoint you're testing the same number of times as the –parallel-max parameter.  So in our case, it would contain:

url = "https://pathtoapiendpoint"
url = "https://pathtoapiendpoint"
url = "https://pathtoapiendpoint"

Check how your application behaves and make appropriate changes to maintain concurrency if you're worried about this happening.  There are various approaches you can use to make sure concurrency is maintained such as appending the old value of the database record into your where clause when updating to see if the data has already been changed within the timeframe of the request being processed. 

Or, you can use persistent virtual columns like this:

https://stackoverflow.com/questions/54338201/mysql-prevent-insertion-of-record-if-id-and-timestamp-unique-combo-constraint 

Moving a Website to Another Server – Redirect Traffic to the New Server While DNS Propagates (for No Downtime)

If you're migrating a website from one server to another and have updated the DNS for the domain to point to the new server, some traffic will still be directed to the old server due to DNS caching.  So, while the DNS changes propagate over the internet (can take up to three days), you can still redirect traffic to the new server from the old server so that you won't suffer any downtime. 

On the old server, run these commands to redirect web traffic on port 80 (http) and port 443 (https) to the new server (adjust the {DESTINATION_IP_ADDRESS} variable accordingly):

echo 1 >/proc/sys/net/ipv4/ip_forward
iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination {DESTINATION_IP_ADDRESS}:80
iptables -t nat -A PREROUTING -p tcp --dport 443 -j DNAT --to-destination {DESTINATION_IP_ADDRESS}:443
iptables -t nat -A POSTROUTING -p tcp -d {DESTINATION_IP_ADDRESS} --dport 80 -j MASQUERADE
iptables -t nat -A POSTROUTING -p tcp -d {DESTINATION_IP_ADDRESS} --dport 443 -j MASQUERADE

Reference:  https://serverfault.com/questions/371833/changing-servers-redirect-to-new-ip-no-downtime#371870

Dual Boot Linux (Ubuntu 22.04) and Windows 11 on Modern Systems – UEFI

In order to setup a dual boot of Windows 11 and Ubuntu 22.04 on a modern system that uses UEFI, follow these steps.

1. Install Windows 11 first leaving some unpartitioned space (at least 60GB is my recommendation) on the drive you're installing Windows on.
2. Boot up the Ubuntu installer.
3. During installation, you'll be presented with an Installation Type options screen.  Choose "Something else". 

4. On the next screen, you'll see a list of drives and partitions.  On the same drive you installed Windows, create 3 new partitions. 
   1. Create an EXT4 partition for the / mount point at least 40GB in size (this is the main drive for Linux files).
   2. Create a SWAP partition at least 18GB in size.
   3. Create an EFI partition at least 500MB in size.  This is extremely important in order to get grub to install properly. 
5. Leave the "Device for boot loader installation" set as the top level drive that Windows and Ubuntu was / is being installed on.  You should not select an individual partition here.

6. Complete the installation process. 
7. You might need to change the UEFI boot order in the BIOS of your system to boot Ubuntu / Linux first versus booting the Windows EFI partition.  Since you created an EFI partition for your Linux install, it should show up as a bootable option in the bios.  Set / adjust accordingly.
8. That's it!

Creating SSL PFX Certificate for IIS Windows

To create a PFX certificate file you can import into IIS on Windows from an openssl private key and certificate file on Linux, use the below command:

openssl pkcs12 -export -legacy -out iis_certificate.pfx -inkey your_private_key.key -in your_cert.crt -certfile your_chain.crt

Restoring Areca Backups

The first step to restoring an Areca backup image is to map the network drives as they were on the computer you made the backup from (if you were using network drives to store the backup).  If you can't remember how the network drives were initially configured or mapped, proceed to the next step, and Areca will eventually tell you which drive is missing.  Once the drives have been remapped as before, and if the backup file is no longer stored on that mapped drive, copy your Areca backup folder (for example, in my case, the folder named 1878606550) to the backup drive location.   

In order to restore an Areca backup archive onto another computer, you need to copy the bcfg file located in the areca_config_backup folder to the Areca workspace directory on the computer you're attempting to restore the files on.  Once you've done that, you can restart Areca, and you'll be prompted to provide the encryption key.  Enter it here.

Assuming the drives exist as they did on the previous computer and the backup folder exists where the backups were being stored, you should be able to view the files within the Archives tab.  Right click on the backup and choose "Recover".  Follow this wizard, and the files will be unencrypted and extracted.   

RAID Synchronization CRON Job Affecting Performance

For some FakeRaid configurations, CentOS 7 and newer variants may run a RAID synchronization job configured in the /etc/cron.d directory in a file named raid-check.

This job is responsible for making sure the RAID array is in sync across all drives.  It runs by default every week on Sunday at 1 AM.

# Run system wide raid-check once a week on Sunday at 1am by default

However, this was not a convenient time for my users, as they were gaming at this time, so rather than affect server performance, I changed the cronjob to:

0 5 1 * * root /usr/bin/test $(/usr/bin/date +\%u) -ne 6 && /usr/sbin/raid-check

Thus, the sync job now runs once a month on the 1st at 5 AM.  And, it will not run if the day of the week is a Saturday.  This applies to several of my C1100 servers.

Fix for Older SSH Keys Not Working on Windows Git

If your old SSH keys are not working on Windows after installing the latest Git client and tools, 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 C:\Program Files\Git\etc\ssh\ssh_config file:

Host *
	PubkeyAcceptedKeyTypes +ssh-rsa

That's it.  It will work again. 

Similar fix for Linux: https://blog.eamster.tk/fix-for-ssh-keys-not-working-on-newer-versions-of-debian-ubuntu/

Drive cloning — Larger to smaller hard drive (or SSD) using Clonezilla

Requirements:

Ability to use Clonezilla

Ability to use Gparted

Disable Fast Boot in Windows 10 / Windows 11 – Before moving / resizing partitions with GParted

Ability to do simple arithmetic (remember arithmetic?)

Procedure:

Using Clonezilla, I’ve always heard you can only clone a hard drive to a drive that is the same size or bigger. Not so. I just cloned a 250 GB to a 240 GB, and I suspect this method will work for any size drive difference. The only requirement is that the sum of the size of the partitions on the source drive must not be larger than the total size of the target drive. To make this the case, it will probably be necessary to resize the partitions on the source drive using Gparted. Of course, be aware that Gparted can only reduce the size of any partition to no smaller than the amount of data that it holds (known as “used space”).

In my case, the source drive is 250 GB with four partitions – one for Windows XP, one for Windows 7, one for Linux, and one for Linux swap. This is a triple boot PC using Grub2 as the initial boot manager for Linux, and Windows 7 as the secondary boot manager for both XP and 7. So this was a rather unusual boot scenario that I needed Clonezilla to clone correctly.

The target drive was a 240 GB SSD, which should be blank (unpartitioned). If it is not blank, that’s fine, as everything (data and partitions) will be erased by the cloning process automatically by Clonezilla. It will warn you about this several times. So if the target drive has anything on it you want to save, save it before starting the cloning process.

The target drive is 10 GB smaller than the source drive, so the first thing I needed to do was reduce the size of one or more partitions on the source drive by a total of 10+ GB using Gparted. I had over 30 GB of free space on the Windows 7 partition, so I reduced its partition size by 10 GB. I also deleted the 4 GB Linux swap partition after I reconfigured Linux to use a swap file instead of a swap partition, which meant I reduced the size of my partitions by 14 GB overall. Finally, also using Gparted on the source drive, I then moved all the unallocated space to the end of the drive. In my case, to move the unallocated space to the end, I simply moved the Linux partition “to the left” to immediately follow the Windows 7 partition. This is important, as you want your partitions to be contiguous from the beginning of the source drive so that they will all fit on the smaller target drive. The unallocated space, which is now all at the end of the source drive, will be ignored by Clonezilla, as if it isn’t even there. In that way, the source drive appears to be smaller than the target drive to Clonezilla.

Once the source drive is configured like this, it is time to have both source and target drives attached to the computer and boot into Clonezilla from CD (or USB). We are going to do a drive-to-drive copy, using expert mode.

We choose expert mode so we can select the -icds and -rvd (windows and NTFS drives only) options when prompted, in addition to keeping all the pre-set default options.

Finally, when prompted on how to handle cloning the partition table, choose “Use the partition table from the source drive.”

Pay attention to the warnings Clonezilla gives you about erasing the target drive, verifying that the drive it will be erasing is indeed your target drive and not the source drive. Then let Clonezilla do the cloning, and if there are no errors reported due to bad sectors or other unforeseen problems, you should end up with a bootable clone of your once-larger source drive on the smaller target drive. It worked for me.

Image source