diff options
-rw-r--r-- | documentation/poky-ref-manual/ref-variables.xml | 40 |
1 files changed, 32 insertions, 8 deletions
diff --git a/documentation/poky-ref-manual/ref-variables.xml b/documentation/poky-ref-manual/ref-variables.xml index 128f27dafd..305ffd1480 100644 --- a/documentation/poky-ref-manual/ref-variables.xml +++ b/documentation/poky-ref-manual/ref-variables.xml | |||
@@ -513,11 +513,21 @@ | |||
513 | <glossentry id='var-IMAGE_OVERHEAD_FACTOR'><glossterm>IMAGE_OVERHEAD_FACTOR</glossterm> | 513 | <glossentry id='var-IMAGE_OVERHEAD_FACTOR'><glossterm>IMAGE_OVERHEAD_FACTOR</glossterm> |
514 | <glossdef> | 514 | <glossdef> |
515 | <para> | 515 | <para> |
516 | Defines a multiplier that the build system might apply to the initial image | 516 | Defines a multiplier that the build system applies to the initial image |
517 | size to create free disk space in the image as overhead. | 517 | size for cases when the multiplier times the returned disk usage value |
518 | for the image is greater than the sum of | ||
519 | <filename><link linkend='var-IMAGE_ROOTFS_SIZE'>IMAGE_ROOTFS_SIZE</link></filename> | ||
520 | and | ||
521 | <filename><link linkend='var-IMAGE_ROOTFS_EXTRA_SPACE'>IMAGE_ROOTFS_EXTRA_SPACE</link></filename>. | ||
522 | The result of the multiplier applied to the initial image size creates | ||
523 | free disk space in the image as overhead. | ||
518 | By default, the build process uses a multiplier of 1.3 for this variable. | 524 | 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 | 525 | 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. | 526 | method is used to determine the final generated image size. |
527 | You should be aware that post install scripts and the package management | ||
528 | system uses disk space inside this overhead area. | ||
529 | Consequently, the multiplier does not produce an image with | ||
530 | all the theoretical free disk space. | ||
521 | See <filename><link linkend='var-IMAGE_ROOTFS_SIZE'>IMAGE_ROOTFS_SIZE</link></filename> | 531 | 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. | 532 | for information on how the build system determines the overall image size. |
523 | </para> | 533 | </para> |
@@ -576,17 +586,31 @@ | |||
576 | Programatically, the build system determines the final size of the | 586 | Programatically, the build system determines the final size of the |
577 | generated image as follows: | 587 | generated image as follows: |
578 | <literallayout class='monospaced'> | 588 | <literallayout class='monospaced'> |
579 | if (du * overhead) < IMAGE_ROOTFS_SIZE: | 589 | if (image-du * overhead) < rootfs-size: |
580 | IMAGE_ROOTFS_SIZE = IMAGE_ROOTFS_SIZE + xspace | 590 | internal-rootfs-size = rootfs-size + xspace |
581 | else: | 591 | else: |
582 | IMAGE_ROOTFS_SIZE = (du * overhead) + xspace | 592 | internal-rootfs-size = (image-du * overhead) + xspace |
593 | |||
594 | where: | ||
595 | |||
596 | image-du = Returned value of the du command on | ||
597 | the image. | ||
598 | |||
599 | overhead = IMAGE_OVERHEAD_FACTOR | ||
600 | |||
601 | rootfs-size = IMAGE_ROOTFS_SIZE | ||
602 | |||
603 | internal-rootfs-size = Initial root filesystem | ||
604 | size before any modifications. | ||
605 | |||
606 | xspace = IMAGE_ROOTFS_EXTRA_SPACE | ||
583 | </literallayout> | 607 | </literallayout> |
584 | In the above example, <filename>overhead</filename> is defined by the | 608 | <!-- In the above example, <filename>overhead</filename> is defined by the |
585 | <filename><link linkend='var-IMAGE_OVERHEAD_FACTOR'>IMAGE_OVERHEAD_FACTOR</link></filename> | 609 | <filename><link linkend='var-IMAGE_OVERHEAD_FACTOR'>IMAGE_OVERHEAD_FACTOR</link></filename> |
586 | variable, <filename>xspace</filename> is defined by the | 610 | variable, <filename>xspace</filename> is defined by the |
587 | <filename><link linkend='var-IMAGE_ROOTFS_EXTRA_SPACE'>IMAGE_ROOTFS_EXTRA_SPACE</link></filename> | 611 | <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 | 612 | variable, and <filename>du</filename> is the results of the disk usage command |
589 | on the initially generated image. | 613 | on the initially generated image. --> |
590 | </para> | 614 | </para> |
591 | </glossdef> | 615 | </glossdef> |
592 | </glossentry> | 616 | </glossentry> |