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The psplash program has a mechanism for showing updates graphically in the form of a progress bar. The program is told when and how much to fill the progress bar via text messages sent through a fifo. If the fifo doesn't exist when the psplash program starts, it tries to create it. If the fifo doesn't exist or can't be created, the psplash program will refuse to run. In various circumstances when a system is booted for the very first time, the filesystem is mounted, initially, read-only. As a result the psplash program is not able to run. On systems where the root filesystem is not meant to be read-only, it will eventually be mounted read-write. Therefore the psplash program can run on shutdown, and all subsequent boots. Only the first boot is affected. If a fifo is created and included in the filesystem as part of the recipe, then filesystems that are meant to be read-only will have psplash work, as well as the cases where (on first boot) a read-write filesystem is initially mounted read-only. NOTE: this is only an issue with sysvinit, and non-qemu machines. systemd-based systems don't suffer from this first-boot issue, and neither do the qemu machines. NOTE 2: when psplash is done, it removes the fifo. Therefore the fifo used for communicating with psplash doesn't hang around unnecessarily in the filesystem. (From OE-Core rev: d20978f9bce3caf473f5b4f55d645dbeabc1642d) Signed-off-by: Trevor Woerner <twoerner@gmail.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
QEMU Emulation Targets ====================== To simplify development, the build system supports building images to work with the QEMU emulator in system emulation mode. Several architectures are currently supported in 32 and 64 bit variants: * ARM (qemuarm + qemuarm64) * x86 (qemux86 + qemux86-64) * PowerPC (qemuppc only) * MIPS (qemumips + qemumips64) Use of the QEMU images is covered in the Yocto Project Reference Manual. The appropriate MACHINE variable value corresponding to the target is given in brackets.