Please see below output: In below output, the inode numbers of /dev and /run are same and equal to 2. The inode numbers of ./ and ../(could be a special case as ../ should point to ./) are also 2 and 2. How can dev and run and / have the same inode as there contents are entirely different.
$ll -i
total 84
2 drwxr-xr-x 20 root root 4096 Aug 18 01:21 ./
2 drwxr-xr-x 20 root root 4096 Aug 18 01:21 ../
12 lrwxrwxrwx 1 root root 7 Aug 18 01:19 bin -> usr/bin/
1048577 drwxr-xr-x 4 root root 4096 Sep 1 15:53 boot/
5636097 drwxr-xr-x 2 root root 4096 Aug 18 01:21 cdrom/
2 drwxr-xr-x 23 root root 4920 Sep 3 11:20 dev/
262145 drwxr-xr-x 144 root root 12288 Sep 3 09:34 etc/
524289 drwxr-xr-x 3 root root 4096 Aug 18 01:22 home/
13 lrwxrwxrwx 1 root root 7 Aug 18 01:19 lib -> usr/lib/
14 lrwxrwxrwx 1 root root 9 Aug 18 01:19 lib32 -> usr/lib32/
15 lrwxrwxrwx 1 root root 9 Aug 18 01:19 lib64 -> usr/lib64/
16 lrwxrwxrwx 1 root root 10 Aug 18 01:19 libx32 -> usr/libx32/
11 drwx------ 2 root root 16384 Aug 18 01:18 lost+found/
3932161 drwxr-xr-x 5 root root 4096 Aug 18 17:23 media/
1572865 drwxr-xr-x 7 root root 4096 Sep 2 14:19 mnt/
9175041 drwxr-xr-x 4 root root 4096 Aug 28 23:46 opt/
1 dr-xr-xr-x 359 root root 0 Sep 3 10:18 proc/
5505025 drwx------ 11 root root 4096 Sep 1 17:49 root/
2 drwxr-xr-x 43 root root 1320 Sep 3 11:24 run/
17 lrwxrwxrwx 1 root root 8 Aug 18 01:19 sbin -> usr/sbin/
2097153 drwxr-xr-x 11 root root 4096 Aug 26 20:34 snap/
655361 drwxr-xr-x 2 root root 4096 Jul 31 21:57 srv/
1 dr-xr-xr-x 13 root root 0 Sep 3 10:18 sys/
4325377 drwxrwxrwt 22 root root 4096 Sep 3 11:25 tmp/
1310721 drwxr-xr-x 14 root root 4096 Jul 31 21:58 usr/
8388609 drwxr-xr-x 14 root root 4096 Jul 31 22:05 var/
Same with /sys and /proc. There contents are different but they share the same inode.
Note: I have only one ext4 partition for entire system. And swap is off, though i don't think this matters.
Edit - The already asked Q pointed by Stephen answers to good extent. Why do the directories /home, /usr, /var, etc. all have the same inode number (2)?
But I am interested in knowing few more details regarding how this works.
At the time of Linux installation, i have mentioned only one filesystem (/dev/sda1 -> ext4 -> / ). So for dev, run, proc, sys - Linux is creating these addition FS which is now inferable.
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).
