The first thing to do is ignore the tutorial. You do not need to create a new user, but you definitely do need to change the default password.
As far as "undoing" the command, you need to login to your Pi from the new account the tutorial writer had you create, and re-set the password for user pi. Once you're logged in as the other user (and ...
There is no easy way to do this out of the box. With systemd you have to listen to D-Bus messages to find out when a connection is established. Try networkd-dispatcher, as suggested in the post.
You can run scripts depending on the link operational status. Interface name, among some other parameters, is transmitted to your script as an IFACE environment ...
The problem is this:
/busybox: ELF 64-bit [...] dynamically linked
This is totally normal -- I suspect you have some idea of what this refers to, since you tried ldd on it -- but of course what it was linked to when compiled were 64-bit userland libraries that you do not have.
There are two things you can try:
Not metadata, "file sync." It's an option for dd, not a command, and it makes sure that disk output is flushed to the file system as opposed to being buffered by the OS before dd exits. (It does also make sure the file system metadata is up to date with respect to the dd operation.)
You need a computer with which you can read and write to the SD root filesystem (the second partition in Raspbian/RpiOS) for what I am suggesting.
Read this about how to disable the root password. This would allow you to login root and make whatever changes, such as passwd --unlock pi.
Check if your kernel is built with CONFIG_REGMAP_IRQ=Y. If not, you will not be able to map IRQs to CPUs.
Bear in mind that even if IRQ mapping is enabled, there may be hardware limitation preventing a particular IRQ from being remapped. There are interrupts which are specific to a given core (a prime example is the division by zero IRQ in x86).
Edit: I have ...
wiringSerial is part of wiringPi.
wiringPi is an "Arduino" like C library to control the GPIO.
wiringSerial is a simple wrapper around the underlying Linux serial driver. It simplifies some operations. Look at the source code if you need details.
Note that wiringPi is deprecated (i.e. no longer being developed or supported by its author).
Just wanted to point out a few problems with your script.
First, if you're doing this directly on your root FS, be aware that your backup may have filesystem errors because the FS keeps changing as you make the backup of it. Verify that your backup works!
Second, dd uses a tiny default block size of 512 bytes, so I'm actually surprised you got the ...
It's not an error message, it's a directory index.
"Index of /" means "this is the index of the root directory". And "Name Size Date Modified" are the column headers.
But vsftp is unable to list any files. I suspect you have a permissions or file corruption problem.