Lines Matching refs:and
1 ramfs, rootfs and initramfs
10 mechanisms (the page cache and dentry cache) as a dynamically resizable
23 dentries and page cache as usual, but there's nowhere to write them to.
33 ramfs and ramdisk:
37 an area of RAM and used it as backing store for a filesystem. This block
40 fake block device into the page cache (and copying changes back out), as well
41 as creating and destroying dentries. Plus it needed a filesystem driver
42 (such as ext2) to format and interpret this data.
44 Compared to ramfs, this wastes memory (and memory bus bandwidth), creates
45 unnecessary work for the CPU, and pollutes the CPU caches. (There are tricks
47 complicated and turn out to be about as expensive as the copying anyway.)
49 since all file access goes through the page and dentry caches. The RAM
53 loopback devices offered a more flexible and convenient way to create
57 ramfs and tmpfs:
61 up all memory, and the VM can't free it because the VM thinks that files
66 A ramfs derivative called tmpfs was created to add size limits, and the ability
76 to check for and handle an empty list, it's smaller and simpler for the kernel
79 Most systems just mount another filesystem over rootfs and ignore it. The
91 checks to see if rootfs contains a file "init", and if so it executes it as PID
93 rest of the way up, including locating and mounting the real root device (if
96 to locate and mount a root partition, then exec some variant of /sbin/init
108 see cpio(1) and Documentation/early-userspace/buffer-format.txt). The
110 __init text and data that can be discarded during the boot process.
113 some setup and then returned to the kernel, while the init program from
115 off control it can overmount / with a new root device and exec another init
118 - When switching another root device, initrd would pivot_root and then
123 stdin/stdout/stderr to the new /dev/console, and exec the new init.
125 Since this is a remarkably persnickety process (and involves deleting
134 archive and links it into the resulting kernel binary. By default, this
138 and living in usr/Kconfig) can be used to specify a source for the
160 two example "file" entries expect to find files named "init.sh" and "busybox" in
167 scripts/gen_initramfs_list.sh), and proceeds to package up that directory
170 entirely self-contained, and the kernel's boot-time extractor is also
187 # Copyright 2006 Rob Landley <rob@landley.net> and TimeSys Corporation.
219 will autodetect the type (initramfs, not initrd) and extract the external cpio
236 If you don't already understand what shared libraries, devices, and paths
237 you need to get a minimal root filesystem up and running, here are some
247 I use uClibc (http://www.uclibc.org) and busybox (http://www.busybox.net)
248 myself. These are LGPL and GPL, respectively. (A self-contained initramfs
257 program as init, and test it under an emulator like qemu (www.qemu.org) or
276 "init=/bin/sh". The initramfs equivalent is "rdinit=/bin/sh", and it's
290 The quick and dirty summary version (which is no substitute for reading
293 1) cpio is a standard. It's decades old (from the AT&T days), and already
301 either way about the archive format, and there are alternative tools,
306 2) The cpio archive format chosen by the kernel is simpler and cleaner (and
307 thus easier to create and parse) than any of the (literally dozens of)
309 explained in buffer-format.txt, created in usr/gen_init_cpio.c, and
314 Windows standardizing on zip. Linux is not part of either, and is free
318 something brand new. The kernel provides its own tools to create and
322 5) Al Viro made the decision (quote: "tar is ugly as hell and not going to be
332 and, most importantly, designed and implemented the initramfs code.
340 smooth transition and allowing early boot functionality to gradually move to
343 The move to early userspace is necessary because finding and mounting the real
347 media, with dynamically allocated major/minor numbers and persistent naming
350 and so on.
353 in userspace. Both klibc and busybox/uClibc are working on simple initramfs
358 be migrated into a default initramfs, automatically created and used by the