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| -rw-r--r-- | man/bootup.xml | 37 |
1 files changed, 22 insertions, 15 deletions
diff --git a/man/bootup.xml b/man/bootup.xml index 386af9e4de..9468a61319 100644 --- a/man/bootup.xml +++ b/man/bootup.xml @@ -23,22 +23,29 @@ <refsect1> <title>Description</title> - <para>A number of different components are involved in the system - boot. Immediately after power-up, the system BIOS will do minimal - hardware initialization, and hand control over to a boot loader - stored on a persistent storage device. This boot loader will then - invoke an OS kernel from disk (or the network). In the Linux case, - this kernel (optionally) extracts and executes an initial RAM disk - image (initrd), such as generated by + <para>A number of different components are involved in the boot of a Linux system. Immediately after + power-up, the system firmware will do minimal hardware initialization, and hand control over to a boot + loader (e.g. + <citerefentry><refentrytitle>systemd-boot</refentrytitle><manvolnum>7</manvolnum></citerefentry> or + <ulink url="https://www.gnu.org/software/grub/">GRUB</ulink>) stored on a persistent storage device. This + boot loader will then invoke an OS kernel from disk (or the network). On systems using EFI or other types + of firmware, this firmware may also load the kernel directly.</para> + + <para>The kernel (optionally) mounts an in-memory file system, often generated by <citerefentry project='die-net'><refentrytitle>dracut</refentrytitle><manvolnum>8</manvolnum></citerefentry>, - which looks for the root file system (possibly using - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> - for this). After the root file system is found and mounted, the - initrd hands over control to the host's system manager (such as - <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>) - stored on the OS image, which is then responsible for probing all - remaining hardware, mounting all necessary file systems and - spawning all configured services.</para> + which looks for the root file system. Nowadays this is usually implemented as an initramfs — a compressed + archive which is extracted when the kernel boots up into a lightweight in-memory file system based on + tmpfs, but in the past normal file systems using an in-memory block device (ramdisk) were used, and the + name "initrd" is still used to describe both concepts. It's the boot loader or the firmware that loads + both the kernel and initrd/initramfs images into memory, but the kernel which interprets it as a file + system. <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> may + be used to manage services in the initrd, similarly to the real system.</para> + + <para>After the root file system is found and mounted, the initrd hands over control to the host's system + manager (such as + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>) stored in + the root file system, which is then responsible for probing all remaining hardware, mounting all + necessary file systems and spawning all configured services.</para> <para>On shutdown, the system manager stops all services, unmounts all file systems (detaching the storage technologies backing |