openstack/diskimage-builder
Code Issues Proposed changes

Document byte-to-inode ratio

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End user docs would benefit from a section about the byte-to-inode
ratio, and why it's set the way it is. This update explains why
and how to manipulate the ratio depending on the intended use.

Change-Id: Iffb5ef6f4c7c74f4aa6e25912d4991d7a611c8fe
Closes-bug: 1512841
This commit is contained in:
Abel Lopez 2015-12-15 15:45:36 -08:00
parent d716893e30
commit 5e9c451d5f
1 changed files with 17 additions and 0 deletions
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17
doc/source/user_guide/building_an_image.rst
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@ -54,3 +54,20 @@ formats are:
* vhd * vhd
* docker * docker
* raw * raw
Filesystem Caveat
-----------------
By default, disk-image-create uses a 4k byte-to-inode ratio when creating the
filesystem in the image. This allows large 'whole-system' images to utilize
several TB disks without exhausting inodes. In contrast, when creating images
intended for tenant instances, this ratio consumes more disk space than an
end-user would expect (e.g. a 50GB root disk has 47GB avail.). If the image is
intended to run within a tens to hundrededs of gigabyte disk, setting the
byte-to-inode ratio to the ext4 default of 16k will allow for more usable space
on the instance. The default can be overridden by passing --mkfs-options like
this::
disk-image-create --mkfs-options '-i 16384' <distro> vm