what is 1K-blocks in df, and how to calculate Use percentage?
I have search many and not found 1K-blocks meaning in df command(gnu), but I have calculated and think it equals to 1K Byte? Is there a offical explanation?
Then how to calculate the Used Percentage?
For example:
tankywoo@gentoo-jl::~/ » df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 15G 5.9G 8.2G 42% /
tankywoo@gentoo-jl::~/ » df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sda3 15481840 6163320 8532088 42% /In my local machine, I know there is reserved space.
Used is 6163320, Avail is 8532088, so:
I think Used% should be (15481840-8532088)/15481740 = 44.88%, not 42%.
So how to get the result 42%?
1 Answer
The 1K block in GNU coreutils df(1) means 1024 bytes. Confirmed by taking a quick look at GNU coreutils, version 8.13, source code:
964 if (human_output_opts == -1)
965 {
966 if (posix_format)
967 {
968 human_output_opts = 0;
969 output_block_size = (getenv ("POSIXLY_CORRECT") ? 512 : 1024);
970 }
971 else
972 human_options (getenv ("DF_BLOCK_SIZE"),
973 &human_output_opts, &output_block_size);
974 }As you can see, default output block size is 1024, unless environment variable POSIXLY_CORRECT is set.
When calculating used percentage, df(1) subtracts reserved space/blocks for root user from the available space, when underlying filesystem supports reserved space/blocks (most do):
529 if (known_value (total) && known_value (available_to_root))
530 {
531 used = total - available_to_root;
532 negate_used = (total < available_to_root);
533 }To sum this up, the official authority in this and every case is the source code.
1
