Linux / Unix: Find Inode Of a File Command

ls Command: Display Inode

$ ls -li filename
$ ls -li /etc/resolv.conf
Sample outputs:
25766494 -rwxr-xr-x 1 root root 332 May 5 14:14 /etc/resolv.conf
25766494 is inode number and the -i option displays the index number (inode) of /etc/resolv.conf file.

stat Command: Display Inode

You can also use the stat command as follows:
$ stat fileName-Here
$ stat /etc/passwd
Sample outputs:

  File: `/etc/passwd'
  Size: 1644      	Blocks: 8          IO Block: 4096   regular file
Device: fe01h/65025d	Inode: 25766495    Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2012-05-05 16:29:42.000000000 +0530
Modify: 2012-05-05 16:29:20.000000000 +0530
Change: 2012-05-05 16:29:21.000000000 +0530