By using the tune2fs tool with the option, -l, the inode size of the filesystem could be seen. Using the same option, other information of the filesystem superblock can also be seen. The superblock contains information about the filesystem, such as the number of free blocks available, and the number of mounts, that may be useful for tuning purposes.
Here is an example how a user can specify the -l option. The example used here is of RHEL 7 system:
# tune2fs -l /dev/sda1 tune2fs 1.42.9 (28-Dec-2013) Filesystem volume name: [none] Last mounted on: /boot Filesystem UUID: 1a678f4f-85e4-43c6-b4b3-af1a732510ac Filesystem magic number: 0xEF53 Filesystem revision #: 1 (dynamic) Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Filesystem flags: signed_directory_hash Default mount options: user_xattr acl Filesystem state: clean Errors behavior: Continue Filesystem OS type: Linux Inode count: 65536 Block count: 262144 Reserved block count: 13107 Free blocks: 228732 Free inodes: 65200 First block: 0 Block size: 4096 Fragment size: 4096 Group descriptor size: 64 Reserved GDT blocks: 127 Blocks per group: 32768 Fragments per group: 32768 Inodes per group: 8192 Inode blocks per group: 512 RAID stride: 64 RAID stripe width: 64 Flex block group size: 16 Filesystem created: Tue Jan 26 18:26:17 2016 Last mount time: Sun Jun 26 00:03:14 2016 Last write time: Sun Jun 26 00:03:14 2016 Mount count: 5 Maximum mount count: -1 Last checked: Tue Jan 26 18:26:17 2016 Check interval: 0 ([none]) Lifetime writes: 176 MB Reserved blocks uid: 0 (user root) Reserved blocks gid: 0 (group root) First inode: 11 Inode size: 256 Required extra isize: 28 Desired extra isize: 28 Journal inode: 8 Default directory hash: half_md4 Directory Hash Seed: 27bb8d92-09a4-4734-89b8-f767a5f34fb3 Journal backup: inode blocks
To get the size of inode, use :
# tune2fs -l /dev/sda1 | grep -i inode Filesystem features: has_journal ext_attr resize_inode dir_index filetype needs_recovery extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize Inode count: 65536 Free inodes: 65200 Inodes per group: 8192 Inode blocks per group: 512 First inode: 11 Inode size: 256 Journal inode: 8 Journal backup: inode blocks
As shown above the inode size in RHEL 7 on ext4 system is 256 bytes.
You can also use the df -i command to get the total number of inodes available and how many of them are already utilized.
# df -i /dev/sda1 Filesystem Inodes IUsed IFree IUse% Mounted on /dev/sda1 65536 1919 63617 3% /boot
How to calculate number of inode on ext4/etx3 FS will have before creating it?
As it is written in the man pages the value is based number of blocks and the bytes-per-inode ratio bytes-per-inode = (blocks/inodes) * block_size.
-N number-of-inodes
Overrides the default calculation of the number of inodes that should be reserved for
the filesystem (which is based on the number of blocks and the bytes per-inode ratio).
This allows the user to specify the number of desired inodes directly. To check how many inodes you will have, use -n option with mkfs.ext3/4.
# mkfs.ext4 -n /dev/sda
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=512 blocks
32768 inodes, 131072 blocks
6553 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=33685504
16 block groups
8192 blocks per group, 8192 fragments per group
2048 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729