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authorScott Rifenbark <scott.m.rifenbark@intel.com>2012-01-05 09:52:18 -0600
committerRichard Purdie <richard.purdie@linuxfoundation.org>2012-01-06 12:13:12 +0000
commit03df4ce0938673b40eeb13bd7f52be05285ce1fe (patch)
treeb2b268da6bf885bbe458278c879fd505f9bb7437 /documentation
parent01d5729e13b8688b7238bf763dfd808df5808005 (diff)
downloadpoky-03df4ce0938673b40eeb13bd7f52be05285ce1fe.tar.gz
documentation/poky-ref-manual/ref-variables.xml: image size glossary
I added three new glossary entries for how the build process figures out the image size. Entries are for IMAGE_ROOTFS_SIZE, IMAGE_OVERHEAD_FACTOR, and IMAGE_ROOTFS_EXTRA_SPACE. I still need to create a usage section for this topic. Likely this will be in the development manual in a new chapter I am thinking about. Fixes [YOCTO #1110] partially. (From yocto-docs rev: ec6b9d77d10a95f0a2d460dca3cf8eab5dfbf0c0) Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Diffstat (limited to 'documentation')
-rw-r--r--documentation/poky-ref-manual/ref-variables.xml81
1 files changed, 81 insertions, 0 deletions
diff --git a/documentation/poky-ref-manual/ref-variables.xml b/documentation/poky-ref-manual/ref-variables.xml
index 4da61ff576..128f27dafd 100644
--- a/documentation/poky-ref-manual/ref-variables.xml
+++ b/documentation/poky-ref-manual/ref-variables.xml
@@ -510,6 +510,87 @@
510 </glossdef> 510 </glossdef>
511 </glossentry> 511 </glossentry>
512 512
513 <glossentry id='var-IMAGE_OVERHEAD_FACTOR'><glossterm>IMAGE_OVERHEAD_FACTOR</glossterm>
514 <glossdef>
515 <para>
516 Defines a multiplier that the build system might apply to the initial image
517 size to create free disk space in the image as overhead.
518 By default, the build process uses a multiplier of 1.3 for this variable.
519 This default value results in 30% free disk space added to the image when this
520 method is used to determine the final generated image size.
521 See <filename><link linkend='var-IMAGE_ROOTFS_SIZE'>IMAGE_ROOTFS_SIZE</link></filename>
522 for information on how the build system determines the overall image size.
523 </para>
524
525 <para>
526 The default 30% free disk space typically gives the image enough room to boot
527 and allows for basic post installs while still leaving a small amount of
528 free disk space.
529 If 30% free space is inadequate, you can increase the default value.
530 For example, the following setting gives you 50% free space added to the image:
531 <literallayout class='monospaced'>
532 IMAGE_OVERHEAD_FACTOR = "1.5"
533 </literallayout>
534 </para>
535
536 <para>
537 Alternatively, you can ensure a specific amount of free disk space is added
538 to the image by using
539 <filename><link linkend='var-IMAGE_ROOTFS_EXTRA_SPACE'>IMAGE_ROOTFS_EXTRA_SPACE</link></filename>
540 the variable.
541 </para>
542 </glossdef>
543 </glossentry>
544
545 <glossentry id='var-IMAGE_ROOTFS_EXTRA_SPACE'><glossterm>IMAGE_ROOTFS_EXTRA_SPACE</glossterm>
546 <glossdef>
547 <para>
548 Defines additional free disk space created in the image in Kbytes.
549 By default, this variable is set to "0".
550 This free disk space is added to the image after the build system determines
551 the image size as described in
552 <filename><link linkend='var-IMAGE_ROOTFS_SIZE'>IMAGE_ROOTFS_SIZE</link></filename>.
553 </para>
554
555 <para>
556 This variable is particularly useful when you want to ensure that a
557 specific amount of free disk space is available on a device after an image
558 is installed and running.
559 For example, to be sure 5 Gbytes of free disk space is available, set the
560 variable as follows:
561 <literallayout class='monospaced'>
562 IMAGE_ROOTFS_EXTRA_SPACE = "5242880"
563 </literallayout>
564 </para>
565 </glossdef>
566 </glossentry>
567
568 <glossentry id='var-IMAGE_ROOTFS_SIZE'><glossterm>IMAGE_ROOTFS_SIZE</glossterm>
569 <glossdef>
570 <para>
571 Defines the size in Kbytes for the generated image.
572 The Yocto Project build system determines the final size for the generated
573 image using an algorithm that takes into account the initial disk space used
574 for the generated image, a requested size for the image, and requested
575 additional free disk space to be added to the image.
576 Programatically, the build system determines the final size of the
577 generated image as follows:
578 <literallayout class='monospaced'>
579 if (du * overhead) &lt; IMAGE_ROOTFS_SIZE:
580 IMAGE_ROOTFS_SIZE = IMAGE_ROOTFS_SIZE + xspace
581 else:
582 IMAGE_ROOTFS_SIZE = (du * overhead) + xspace
583 </literallayout>
584 In the above example, <filename>overhead</filename> is defined by the
585 <filename><link linkend='var-IMAGE_OVERHEAD_FACTOR'>IMAGE_OVERHEAD_FACTOR</link></filename>
586 variable, <filename>xspace</filename> is defined by the
587 <filename><link linkend='var-IMAGE_ROOTFS_EXTRA_SPACE'>IMAGE_ROOTFS_EXTRA_SPACE</link></filename>
588 variable, and <filename>du</filename> is the results of the disk usage command
589 on the initially generated image.
590 </para>
591 </glossdef>
592 </glossentry>
593
513 <glossentry id='var-INC_PR'><glossterm>INC_PR</glossterm> 594 <glossentry id='var-INC_PR'><glossterm>INC_PR</glossterm>
514 <glossdef> 595 <glossdef>
515 <para>Defines the Package revision. 596 <para>Defines the Package revision.