At the time of Linux installation, i have mentioned only one filesystem (/dev/sda1 -> ext4 -> / ). But for dev, run, proc, sys - Linux is creating addition FS which is inferable from
$ mount sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime) proc on /proc type proc (rw,nosuid,nodev,noexec,relatime) udev on /dev type devtmpfs (rw,nosuid,noexec,relatime,size=12138104k,nr_inodes=3034526,mode=755) devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000) tmpfs on /run type tmpfs (rw,nosuid,nodev,noexec,relatime,size=2433824k,mode=755) /dev/sda4 on / type ext4 (rw,relatime,errors=remount-ro) ...
I am aware that /proc is a Virtual FS and is in memory and not on any HDD/SSD. Could some one explain what is the case with /dev, /run and /sys. Do they exist on HDD (if so what is there location if it can be meaningfully traced).
Based on already asked Q - Why inode numbers of /dev and /run are same as that of /?