Solaris inode size

When a file system is created under the Solaris OS, data structures that contain information about files are also created. Each file has an inode and is identified by an inode number (often referred to as an "i-number" or "inode") in the file system where it resides.

Inodes store information such as user and group ownership, access mode (read, write, execute permissions) and type of file. There is a fixed number of inodes, which indicates the maximum number of files each file system can hold. Typically when a file system is created about 1% of it is devoted to inodes.

Number of Inodes (Files)

The number of bytes per inode specifies the density of inodes in the file system. The number is divided into the total size of the file system to determine the number of inodes to create. Once the inodes are allocated, you cannot change the number without re-creating the file system.

The default number of bytes per inode is 2048 bytes (2 Kbytes) if the file system is less than 1 Gbyte. If the file system is larger than 1 Gbyte, the following formula is used:

File system size bytes per inode
Less than or equal to 1 Gbyte2048
Less than 2 Gbytes4096
Less than 3 Gbytes6144
3 Gbytes up to 1 Tbyte8192
Greater than 1 Tbyte or created with -T option1048576

Displaying inode information

The following table lists a number of commands available in the Solaris OS to display inode information

Command Comments
df -F ufs -o i <disk-path>Display inode utilization
df -g <mount-point>Display inode utilization
ls -iDisplays the inode number information
newfs -Nv <disk-path>Displays the details used for creating the file system.
mkfs -m /dev/rdsk/c0t3d0s5Displays more details, inclusive of nbpi (number of bytes per inode) used for creating the file system.


  • If you have a file system with many symbolic links, they can lower the average file size.
  • If your file system is going to have many small files, you can give this parameter a lower value. Note, however, that having too many inodes is much better than running out of inodes.
  • If you have too few inodes, you could reach the maximum number of files on a disk slice that is practically empty.


Using df -o -i

# df -F ufs -o i /opt
Filesystem             iused   ifree  %iused  Mounted on
/dev/dsk/c0t3d0s5       2506  145590     2%   /opt

When using df -o i, we would add the values from the iused and ifree columns to get the total number of inodes for the given filesystem (2506 + 145590 = 148096).

Using df & mkfs

# df -k /opt
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/dsk/c0t3d0s5     288855   73739  186231    29%    /opt
# mkfs -m /dev/rdsk/c0t3d0s5
mkfs -F ufs -o
nbpi=2066,opt=t,apc=0,gap=0,nrpos=8,maxcontig=16 /dev/rdsk/c0t3d0s5 615600

To find the number of inodes in the filesystem, divide the kbytes by nbpi: (288855 * 1024 / 2066 = 143169)

Using df -g

# df -g /tmp
/tmp   (swap):            4096 block size      4096 frag size
 5522968 total blocks  5522896 free blocks  5522896 available
  203559 total files    203348 free files  78643202 filesys id  /tmp
      tmpfs fstype  0x00000004 flag             255 filename length

In the above example, we can simply look at the free files field.