ext4 filesystem math

genese · 02-23-2018, 01:34 AM

Here is the output of tune2fs for a newly created ext4 filesystem :

Code:

.....
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent 64bit flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash 
Filesystem state:         clean
Inode count:              327680
Block count:              1310208
Reserved block count:     65510
Free blocks:              1251746
.....

Adding free and reserved gives 1317256 blocks free for user root.

That is more than 100% relative to blocks count (1310208).

Any explanation ?

Emerson · 02-23-2018, 03:20 AM

You have 1251746 free blocks, 65510 of them are reserved for root.

pan64 · 02-23-2018, 03:26 AM

yes, the others are used for "housekeeping", so they already contain some information.
You may try to use fdisk to check the block count of the partition too (I assume that will be near to 1310208).

genese · 02-23-2018, 04:34 AM

Quote:

Originally Posted by Emerson

You have 1251746 free blocks, 65510 of them are reserved for root.

It's better like that ;-)

Can you explain how these figures relate to the output of 'df' ?

Code:

Filesystem      4K-blocks  Used Available Use% Mounted on
/dev/mapper/vdb   1256864  5118   1182140   1% /srv

1251746-65510 is 1186236, not 1182140. how can we explain the 1256864 ?