How to find the default block size ?

If you ever want to confirm the block size of any file system of Ubuntu or any other Linux OS, tune2fs command is here to help:

# tune2fs  -l  /dev/sda1  |  grep  Block

Block count: 4980736

Block size: 4096

Blocks per group: 32768

Here, default block size for the file system on /dev/sda1 partition is 4096 bytes, or 4k.

For Solaris, you can use any one command from following:

$ df  -g  /

# fstyp  -v  /dev/dsk/c1t0d0s0  |  grep  ^bsize