==== Check a disk is HDD or SSD (rotational) ====

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You often get **a new PC or laptop** or using another person's computer and you may **not know the disk technology** being used (HDD/SSD). So, on **linux you can** use a **sys kernel file** to find it out.
<code bash>
cat /sys/block/sda/queue/rotational
# 0 means SSD, 1 means HDD
# replace "sda" to your needs
</code>