Add fsync after dd to the documentation (#470)

* Add fsync after dd to the documentation

* Optimize block size

docs/documentation/installation-guide.md

@@ -145,13 +145,15 @@ You need to look for /dev/sda or /dev/sdb or /dev/sdc, which is your target USB.
 After you found out the location of your target USB, navigate to the location of your source ISO. Run the dd command to copy files from ISO to USB: 
 
 ```
-sudo dd if=./AlmaLinux-9.1-x86_64-dvd.iso of=/dev/sdX status=progress
+sudo dd if=./AlmaLinux-9.1-x86_64-dvd.iso of=/dev/sdX status=progress conv=fsync bs=4M
 ```
 
 * `dd`: Start the dd command to write the DVD/CD iso image.
 * `if=AlmaLinux-9.1-x86_64-dvd.iso`: path to the input file.
 * `of=/dev/sdX`: path to destination USB disk/stick (you need to replace 'X').
 * `status=progress`: display a progress bar while writing the image to the USB stick.
+* `conv=fsync`: make sure to finish the writing before returning.
+* `bs=4M`: use blocks of 4 megabytes instead of the default 512 bytes.
 
 :::warning
 This example is for AlmaLinux 9.1. Replace the version with the one you need to work with other AlmaLinux images.
@@ -170,7 +172,7 @@ The cross-platform tool [balenaEtcher](https://www.balena.io/etcher/) is used to
 You can also use `dd` from the CLI:
 
 ```
-sudo dd if=./AlmaLinux-9.1-x86_64-dvd.iso of=/dev/diskXXX status=progress
+sudo dd if=./AlmaLinux-9.1-x86_64-dvd.iso of=/dev/diskXXX status=progress conv=fsync bs=4M
 ```
 
 :::tip