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 @@ + IMAGE_OVERHEAD_FACTOR + + + Defines a multiplier that the build system might apply to the initial image + size to create free disk space in the image as overhead. + By default, the build process uses a multiplier of 1.3 for this variable. + This default value results in 30% free disk space added to the image when this + method is used to determine the final generated image size. + See IMAGE_ROOTFS_SIZE + for information on how the build system determines the overall image size. + + + + The default 30% free disk space typically gives the image enough room to boot + and allows for basic post installs while still leaving a small amount of + free disk space. + If 30% free space is inadequate, you can increase the default value. + For example, the following setting gives you 50% free space added to the image: + + IMAGE_OVERHEAD_FACTOR = "1.5" + + + + + Alternatively, you can ensure a specific amount of free disk space is added + to the image by using + IMAGE_ROOTFS_EXTRA_SPACE + the variable. + + + + + IMAGE_ROOTFS_EXTRA_SPACE + + + Defines additional free disk space created in the image in Kbytes. + By default, this variable is set to "0". + This free disk space is added to the image after the build system determines + the image size as described in + IMAGE_ROOTFS_SIZE. + + + + This variable is particularly useful when you want to ensure that a + specific amount of free disk space is available on a device after an image + is installed and running. + For example, to be sure 5 Gbytes of free disk space is available, set the + variable as follows: + + IMAGE_ROOTFS_EXTRA_SPACE = "5242880" + + + + + + IMAGE_ROOTFS_SIZE + + + Defines the size in Kbytes for the generated image. + The Yocto Project build system determines the final size for the generated + image using an algorithm that takes into account the initial disk space used + for the generated image, a requested size for the image, and requested + additional free disk space to be added to the image. + Programatically, the build system determines the final size of the + generated image as follows: + + if (du * overhead) < IMAGE_ROOTFS_SIZE: + IMAGE_ROOTFS_SIZE = IMAGE_ROOTFS_SIZE + xspace + else: + IMAGE_ROOTFS_SIZE = (du * overhead) + xspace + + In the above example, overhead is defined by the + IMAGE_OVERHEAD_FACTOR + variable, xspace is defined by the + IMAGE_ROOTFS_EXTRA_SPACE + variable, and du is the results of the disk usage command + on the initially generated image. + + + + INC_PR Defines the Package revision.