1 Using the initial RAM disk (initrd) 1 Using the initial RAM disk (initrd)
2 =================================== 2 ===================================
3 3
4 Written 1996,2000 by Werner Almesberger <werner 4 Written 1996,2000 by Werner Almesberger <werner.almesberger@epfl.ch> and
5 Hans Lermen <lermen@fgan.de> 5 Hans Lermen <lermen@fgan.de>
6 6
7 7
8 initrd provides the capability to load a RAM d 8 initrd provides the capability to load a RAM disk by the boot loader.
9 This RAM disk can then be mounted as the root 9 This RAM disk can then be mounted as the root file system and programs
10 can be run from it. Afterwards, a new root fil 10 can be run from it. Afterwards, a new root file system can be mounted
11 from a different device. The previous root (fr 11 from a different device. The previous root (from initrd) is then moved
12 to a directory and can be subsequently unmount 12 to a directory and can be subsequently unmounted.
13 13
14 initrd is mainly designed to allow system star 14 initrd is mainly designed to allow system startup to occur in two phases,
15 where the kernel comes up with a minimum set o 15 where the kernel comes up with a minimum set of compiled-in drivers, and
16 where additional modules are loaded from initr 16 where additional modules are loaded from initrd.
17 17
18 This document gives a brief overview of the us 18 This document gives a brief overview of the use of initrd. A more detailed
19 discussion of the boot process can be found in 19 discussion of the boot process can be found in [#f1]_.
20 20
21 21
22 Operation 22 Operation
23 --------- 23 ---------
24 24
25 When using initrd, the system typically boots 25 When using initrd, the system typically boots as follows:
26 26
27 1) the boot loader loads the kernel and the 27 1) the boot loader loads the kernel and the initial RAM disk
28 2) the kernel converts initrd into a "normal 28 2) the kernel converts initrd into a "normal" RAM disk and
29 frees the memory used by initrd 29 frees the memory used by initrd
30 3) if the root device is not ``/dev/ram0``, 30 3) if the root device is not ``/dev/ram0``, the old (deprecated)
31 change_root procedure is followed. see th 31 change_root procedure is followed. see the "Obsolete root change
32 mechanism" section below. 32 mechanism" section below.
33 4) root device is mounted. if it is ``/dev/r 33 4) root device is mounted. if it is ``/dev/ram0``, the initrd image is
34 then mounted as root 34 then mounted as root
35 5) /sbin/init is executed (this can be any v 35 5) /sbin/init is executed (this can be any valid executable, including
36 shell scripts; it is run with uid 0 and c 36 shell scripts; it is run with uid 0 and can do basically everything
37 init can do). 37 init can do).
38 6) init mounts the "real" root file system 38 6) init mounts the "real" root file system
39 7) init places the root file system at the r 39 7) init places the root file system at the root directory using the
40 pivot_root system call 40 pivot_root system call
41 8) init execs the ``/sbin/init`` on the new 41 8) init execs the ``/sbin/init`` on the new root filesystem, performing
42 the usual boot sequence 42 the usual boot sequence
43 9) the initrd file system is removed 43 9) the initrd file system is removed
44 44
45 Note that changing the root directory does not 45 Note that changing the root directory does not involve unmounting it.
46 It is therefore possible to leave processes ru 46 It is therefore possible to leave processes running on initrd during that
47 procedure. Also note that file systems mounted 47 procedure. Also note that file systems mounted under initrd continue to
48 be accessible. 48 be accessible.
49 49
50 50
51 Boot command-line options 51 Boot command-line options
52 ------------------------- 52 -------------------------
53 53
54 initrd adds the following new options:: 54 initrd adds the following new options::
55 55
56 initrd=<path> (e.g. LOADLIN) 56 initrd=<path> (e.g. LOADLIN)
57 57
58 Loads the specified file as the initial RA 58 Loads the specified file as the initial RAM disk. When using LILO, you
59 have to specify the RAM disk image file in 59 have to specify the RAM disk image file in /etc/lilo.conf, using the
60 INITRD configuration variable. 60 INITRD configuration variable.
61 61
62 noinitrd 62 noinitrd
63 63
64 initrd data is preserved but it is not con 64 initrd data is preserved but it is not converted to a RAM disk and
65 the "normal" root file system is mounted. 65 the "normal" root file system is mounted. initrd data can be read
66 from /dev/initrd. Note that the data in in 66 from /dev/initrd. Note that the data in initrd can have any structure
67 in this case and doesn't necessarily have 67 in this case and doesn't necessarily have to be a file system image.
68 This option is used mainly for debugging. 68 This option is used mainly for debugging.
69 69
70 Note: /dev/initrd is read-only and it can 70 Note: /dev/initrd is read-only and it can only be used once. As soon
71 as the last process has closed it, all dat 71 as the last process has closed it, all data is freed and /dev/initrd
72 can't be opened anymore. 72 can't be opened anymore.
73 73
74 root=/dev/ram0 74 root=/dev/ram0
75 75
76 initrd is mounted as root, and the normal 76 initrd is mounted as root, and the normal boot procedure is followed,
77 with the RAM disk mounted as root. 77 with the RAM disk mounted as root.
78 78
79 Compressed cpio images 79 Compressed cpio images
80 ---------------------- 80 ----------------------
81 81
82 Recent kernels have support for populating a r 82 Recent kernels have support for populating a ramdisk from a compressed cpio
83 archive. On such systems, the creation of a ra 83 archive. On such systems, the creation of a ramdisk image doesn't need to
84 involve special block devices or loopbacks; yo 84 involve special block devices or loopbacks; you merely create a directory on
85 disk with the desired initrd content, cd to th 85 disk with the desired initrd content, cd to that directory, and run (as an
86 example):: 86 example)::
87 87
88 find . | cpio --quiet -H newc -o | gzi 88 find . | cpio --quiet -H newc -o | gzip -9 -n > /boot/imagefile.img
89 89
90 Examining the contents of an existing image fi 90 Examining the contents of an existing image file is just as simple::
91 91
92 mkdir /tmp/imagefile 92 mkdir /tmp/imagefile
93 cd /tmp/imagefile 93 cd /tmp/imagefile
94 gzip -cd /boot/imagefile.img | cpio -i 94 gzip -cd /boot/imagefile.img | cpio -imd --quiet
95 95
96 Installation 96 Installation
97 ------------ 97 ------------
98 98
99 First, a directory for the initrd file system 99 First, a directory for the initrd file system has to be created on the
100 "normal" root file system, e.g.:: 100 "normal" root file system, e.g.::
101 101
102 # mkdir /initrd 102 # mkdir /initrd
103 103
104 The name is not relevant. More details can be 104 The name is not relevant. More details can be found on the
105 :manpage:`pivot_root(2)` man page. 105 :manpage:`pivot_root(2)` man page.
106 106
107 If the root file system is created during the 107 If the root file system is created during the boot procedure (i.e. if
108 you're building an install floppy), the root f 108 you're building an install floppy), the root file system creation
109 procedure should create the ``/initrd`` direct 109 procedure should create the ``/initrd`` directory.
110 110
111 If initrd will not be mounted in some cases, i 111 If initrd will not be mounted in some cases, its content is still
112 accessible if the following device has been cr 112 accessible if the following device has been created::
113 113
114 # mknod /dev/initrd b 1 250 114 # mknod /dev/initrd b 1 250
115 # chmod 400 /dev/initrd 115 # chmod 400 /dev/initrd
116 116
117 Second, the kernel has to be compiled with RAM 117 Second, the kernel has to be compiled with RAM disk support and with
118 support for the initial RAM disk enabled. Also 118 support for the initial RAM disk enabled. Also, at least all components
119 needed to execute programs from initrd (e.g. e 119 needed to execute programs from initrd (e.g. executable format and file
120 system) must be compiled into the kernel. 120 system) must be compiled into the kernel.
121 121
122 Third, you have to create the RAM disk image. 122 Third, you have to create the RAM disk image. This is done by creating a
123 file system on a block device, copying files t 123 file system on a block device, copying files to it as needed, and then
124 copying the content of the block device to the 124 copying the content of the block device to the initrd file. With recent
125 kernels, at least three types of devices are s 125 kernels, at least three types of devices are suitable for that:
126 126
127 - a floppy disk (works everywhere but it's pa 127 - a floppy disk (works everywhere but it's painfully slow)
128 - a RAM disk (fast, but allocates physical me 128 - a RAM disk (fast, but allocates physical memory)
129 - a loopback device (the most elegant solutio 129 - a loopback device (the most elegant solution)
130 130
131 We'll describe the loopback device method: 131 We'll describe the loopback device method:
132 132
133 1) make sure loopback block devices are confi 133 1) make sure loopback block devices are configured into the kernel
134 2) create an empty file system of the appropr 134 2) create an empty file system of the appropriate size, e.g.::
135 135
136 # dd if=/dev/zero of=initrd bs=300k co 136 # dd if=/dev/zero of=initrd bs=300k count=1
137 # mke2fs -F -m0 initrd 137 # mke2fs -F -m0 initrd
138 138
139 (if space is critical, you may want to use 139 (if space is critical, you may want to use the Minix FS instead of Ext2)
140 3) mount the file system, e.g.:: 140 3) mount the file system, e.g.::
141 141
142 # mount -t ext2 -o loop initrd /mnt 142 # mount -t ext2 -o loop initrd /mnt
143 143
144 4) create the console device:: 144 4) create the console device::
145 145
146 # mkdir /mnt/dev 146 # mkdir /mnt/dev
147 # mknod /mnt/dev/console c 5 1 147 # mknod /mnt/dev/console c 5 1
148 148
149 5) copy all the files that are needed to prop 149 5) copy all the files that are needed to properly use the initrd
150 environment. Don't forget the most importa 150 environment. Don't forget the most important file, ``/sbin/init``
151 151
152 .. note:: ``/sbin/init`` permissions must 152 .. note:: ``/sbin/init`` permissions must include "x" (execute).
153 153
154 6) correct operation the initrd environment c 154 6) correct operation the initrd environment can frequently be tested
155 even without rebooting with the command:: 155 even without rebooting with the command::
156 156
157 # chroot /mnt /sbin/init 157 # chroot /mnt /sbin/init
158 158
159 This is of course limited to initrds that 159 This is of course limited to initrds that do not interfere with the
160 general system state (e.g. by reconfigurin 160 general system state (e.g. by reconfiguring network interfaces,
161 overwriting mounted devices, trying to sta 161 overwriting mounted devices, trying to start already running demons,
162 etc. Note however that it is usually possi 162 etc. Note however that it is usually possible to use pivot_root in
163 such a chroot'ed initrd environment.) 163 such a chroot'ed initrd environment.)
164 7) unmount the file system:: 164 7) unmount the file system::
165 165
166 # umount /mnt 166 # umount /mnt
167 167
168 8) the initrd is now in the file "initrd". Op 168 8) the initrd is now in the file "initrd". Optionally, it can now be
169 compressed:: 169 compressed::
170 170
171 # gzip -9 initrd 171 # gzip -9 initrd
172 172
173 For experimenting with initrd, you may want to 173 For experimenting with initrd, you may want to take a rescue floppy and
174 only add a symbolic link from ``/sbin/init`` t 174 only add a symbolic link from ``/sbin/init`` to ``/bin/sh``. Alternatively, you
175 can try the experimental newlib environment [# 175 can try the experimental newlib environment [#f2]_ to create a small
176 initrd. 176 initrd.
177 177
178 Finally, you have to boot the kernel and load 178 Finally, you have to boot the kernel and load initrd. Almost all Linux
179 boot loaders support initrd. Since the boot pr 179 boot loaders support initrd. Since the boot process is still compatible
180 with an older mechanism, the following boot co 180 with an older mechanism, the following boot command line parameters
181 have to be given:: 181 have to be given::
182 182
183 root=/dev/ram0 rw 183 root=/dev/ram0 rw
184 184
185 (rw is only necessary if writing to the initrd 185 (rw is only necessary if writing to the initrd file system.)
186 186
187 With LOADLIN, you simply execute:: 187 With LOADLIN, you simply execute::
188 188
189 LOADLIN <kernel> initrd=<disk_image> 189 LOADLIN <kernel> initrd=<disk_image>
190 190
191 e.g.:: 191 e.g.::
192 192
193 LOADLIN C:\LINUX\BZIMAGE initrd=C:\LIN 193 LOADLIN C:\LINUX\BZIMAGE initrd=C:\LINUX\INITRD.GZ root=/dev/ram0 rw
194 194
195 With LILO, you add the option ``INITRD=<path>` 195 With LILO, you add the option ``INITRD=<path>`` to either the global section
196 or to the section of the respective kernel in 196 or to the section of the respective kernel in ``/etc/lilo.conf``, and pass
197 the options using APPEND, e.g.:: 197 the options using APPEND, e.g.::
198 198
199 image = /bzImage 199 image = /bzImage
200 initrd = /boot/initrd.gz 200 initrd = /boot/initrd.gz
201 append = "root=/dev/ram0 rw" 201 append = "root=/dev/ram0 rw"
202 202
203 and run ``/sbin/lilo`` 203 and run ``/sbin/lilo``
204 204
205 For other boot loaders, please refer to the re 205 For other boot loaders, please refer to the respective documentation.
206 206
207 Now you can boot and enjoy using initrd. 207 Now you can boot and enjoy using initrd.
208 208
209 209
210 Changing the root device 210 Changing the root device
211 ------------------------ 211 ------------------------
212 212
213 When finished with its duties, init typically 213 When finished with its duties, init typically changes the root device
214 and proceeds with starting the Linux system on 214 and proceeds with starting the Linux system on the "real" root device.
215 215
216 The procedure involves the following steps: 216 The procedure involves the following steps:
217 - mounting the new root file system 217 - mounting the new root file system
218 - turning it into the root file system 218 - turning it into the root file system
219 - removing all accesses to the old (initrd) r 219 - removing all accesses to the old (initrd) root file system
220 - unmounting the initrd file system and de-al 220 - unmounting the initrd file system and de-allocating the RAM disk
221 221
222 Mounting the new root file system is easy: it 222 Mounting the new root file system is easy: it just needs to be mounted on
223 a directory under the current root. Example:: 223 a directory under the current root. Example::
224 224
225 # mkdir /new-root 225 # mkdir /new-root
226 # mount -o ro /dev/hda1 /new-root 226 # mount -o ro /dev/hda1 /new-root
227 227
228 The root change is accomplished with the pivot 228 The root change is accomplished with the pivot_root system call, which
229 is also available via the ``pivot_root`` utili 229 is also available via the ``pivot_root`` utility (see :manpage:`pivot_root(8)`
230 man page; ``pivot_root`` is distributed with u 230 man page; ``pivot_root`` is distributed with util-linux version 2.10h or higher
231 [#f3]_). ``pivot_root`` moves the current root 231 [#f3]_). ``pivot_root`` moves the current root to a directory under the new
232 root, and puts the new root at its place. The 232 root, and puts the new root at its place. The directory for the old root
233 must exist before calling ``pivot_root``. Exam 233 must exist before calling ``pivot_root``. Example::
234 234
235 # cd /new-root 235 # cd /new-root
236 # mkdir initrd 236 # mkdir initrd
237 # pivot_root . initrd 237 # pivot_root . initrd
238 238
239 Now, the init process may still access the old 239 Now, the init process may still access the old root via its
240 executable, shared libraries, standard input/o 240 executable, shared libraries, standard input/output/error, and its
241 current root directory. All these references a 241 current root directory. All these references are dropped by the
242 following command:: 242 following command::
243 243
244 # exec chroot . what-follows <dev/cons 244 # exec chroot . what-follows <dev/console >dev/console 2>&1
245 245
246 Where what-follows is a program under the new 246 Where what-follows is a program under the new root, e.g. ``/sbin/init``
247 If the new root file system will be used with 247 If the new root file system will be used with udev and has no valid
248 ``/dev`` directory, udev must be initialized b 248 ``/dev`` directory, udev must be initialized before invoking chroot in order
249 to provide ``/dev/console``. 249 to provide ``/dev/console``.
250 250
251 Note: implementation details of pivot_root may 251 Note: implementation details of pivot_root may change with time. In order
252 to ensure compatibility, the following points 252 to ensure compatibility, the following points should be observed:
253 253
254 - before calling pivot_root, the current dire 254 - before calling pivot_root, the current directory of the invoking
255 process should point to the new root direct 255 process should point to the new root directory
256 - use . as the first argument, and the _relat 256 - use . as the first argument, and the _relative_ path of the directory
257 for the old root as the second argument 257 for the old root as the second argument
258 - a chroot program must be available under th 258 - a chroot program must be available under the old and the new root
259 - chroot to the new root afterwards 259 - chroot to the new root afterwards
260 - use relative paths for dev/console in the e 260 - use relative paths for dev/console in the exec command
261 261
262 Now, the initrd can be unmounted and the memor 262 Now, the initrd can be unmounted and the memory allocated by the RAM
263 disk can be freed:: 263 disk can be freed::
264 264
265 # umount /initrd 265 # umount /initrd
266 # blockdev --flushbufs /dev/ram0 266 # blockdev --flushbufs /dev/ram0
267 267
268 It is also possible to use initrd with an NFS- 268 It is also possible to use initrd with an NFS-mounted root, see the
269 :manpage:`pivot_root(8)` man page for details. 269 :manpage:`pivot_root(8)` man page for details.
270 270
271 271
272 Usage scenarios 272 Usage scenarios
273 --------------- 273 ---------------
274 274
275 The main motivation for implementing initrd wa 275 The main motivation for implementing initrd was to allow for modular
276 kernel configuration at system installation. T 276 kernel configuration at system installation. The procedure would work
277 as follows: 277 as follows:
278 278
279 1) system boots from floppy or other media w 279 1) system boots from floppy or other media with a minimal kernel
280 (e.g. support for RAM disks, initrd, a.ou 280 (e.g. support for RAM disks, initrd, a.out, and the Ext2 FS) and
281 loads initrd 281 loads initrd
282 2) ``/sbin/init`` determines what is needed 282 2) ``/sbin/init`` determines what is needed to (1) mount the "real" root FS
283 (i.e. device type, device drivers, file s 283 (i.e. device type, device drivers, file system) and (2) the
284 distribution media (e.g. CD-ROM, network, 284 distribution media (e.g. CD-ROM, network, tape, ...). This can be
285 done by asking the user, by auto-probing, 285 done by asking the user, by auto-probing, or by using a hybrid
286 approach. 286 approach.
287 3) ``/sbin/init`` loads the necessary kernel 287 3) ``/sbin/init`` loads the necessary kernel modules
288 4) ``/sbin/init`` creates and populates the 288 4) ``/sbin/init`` creates and populates the root file system (this doesn't
289 have to be a very usable system yet) 289 have to be a very usable system yet)
290 5) ``/sbin/init`` invokes ``pivot_root`` to 290 5) ``/sbin/init`` invokes ``pivot_root`` to change the root file system and
291 execs - via chroot - a program that conti 291 execs - via chroot - a program that continues the installation
292 6) the boot loader is installed 292 6) the boot loader is installed
293 7) the boot loader is configured to load an 293 7) the boot loader is configured to load an initrd with the set of
294 modules that was used to bring up the sys 294 modules that was used to bring up the system (e.g. ``/initrd`` can be
295 modified, then unmounted, and finally, th 295 modified, then unmounted, and finally, the image is written from
296 ``/dev/ram0`` or ``/dev/rd/0`` to a file) 296 ``/dev/ram0`` or ``/dev/rd/0`` to a file)
297 8) now the system is bootable and additional 297 8) now the system is bootable and additional installation tasks can be
298 performed 298 performed
299 299
300 The key role of initrd here is to re-use the c 300 The key role of initrd here is to re-use the configuration data during
301 normal system operation without requiring the 301 normal system operation without requiring the use of a bloated "generic"
302 kernel or re-compiling or re-linking the kerne 302 kernel or re-compiling or re-linking the kernel.
303 303
304 A second scenario is for installations where L 304 A second scenario is for installations where Linux runs on systems with
305 different hardware configurations in a single 305 different hardware configurations in a single administrative domain. In
306 such cases, it is desirable to generate only a 306 such cases, it is desirable to generate only a small set of kernels
307 (ideally only one) and to keep the system-spec 307 (ideally only one) and to keep the system-specific part of configuration
308 information as small as possible. In this case 308 information as small as possible. In this case, a common initrd could be
309 generated with all the necessary modules. Then 309 generated with all the necessary modules. Then, only ``/sbin/init`` or a file
310 read by it would have to be different. 310 read by it would have to be different.
311 311
312 A third scenario is more convenient recovery d 312 A third scenario is more convenient recovery disks, because information
313 like the location of the root FS partition doe 313 like the location of the root FS partition doesn't have to be provided at
314 boot time, but the system loaded from initrd c 314 boot time, but the system loaded from initrd can invoke a user-friendly
315 dialog and it can also perform some sanity che 315 dialog and it can also perform some sanity checks (or even some form of
316 auto-detection). 316 auto-detection).
317 317
318 Last not least, CD-ROM distributors may use it 318 Last not least, CD-ROM distributors may use it for better installation
319 from CD, e.g. by using a boot floppy and boots 319 from CD, e.g. by using a boot floppy and bootstrapping a bigger RAM disk
320 via initrd from CD; or by booting via a loader 320 via initrd from CD; or by booting via a loader like ``LOADLIN`` or directly
321 from the CD-ROM, and loading the RAM disk from 321 from the CD-ROM, and loading the RAM disk from CD without need of
322 floppies. 322 floppies.
323 323
324 324
325 Obsolete root change mechanism 325 Obsolete root change mechanism
326 ------------------------------ 326 ------------------------------
327 327
328 The following mechanism was used before the in 328 The following mechanism was used before the introduction of pivot_root.
329 Current kernels still support it, but you shou 329 Current kernels still support it, but you should _not_ rely on its
330 continued availability. 330 continued availability.
331 331
332 It works by mounting the "real" root device (i 332 It works by mounting the "real" root device (i.e. the one set with rdev
333 in the kernel image or with root=... at the bo 333 in the kernel image or with root=... at the boot command line) as the
334 root file system when linuxrc exits. The initr 334 root file system when linuxrc exits. The initrd file system is then
335 unmounted, or, if it is still busy, moved to a 335 unmounted, or, if it is still busy, moved to a directory ``/initrd``, if
336 such a directory exists on the new root file s 336 such a directory exists on the new root file system.
337 337
338 In order to use this mechanism, you do not hav 338 In order to use this mechanism, you do not have to specify the boot
339 command options root, init, or rw. (If specifi 339 command options root, init, or rw. (If specified, they will affect
340 the real root file system, not the initrd envi 340 the real root file system, not the initrd environment.)
341 341
342 If /proc is mounted, the "real" root device ca 342 If /proc is mounted, the "real" root device can be changed from within
343 linuxrc by writing the number of the new root 343 linuxrc by writing the number of the new root FS device to the special
344 file /proc/sys/kernel/real-root-dev, e.g.:: 344 file /proc/sys/kernel/real-root-dev, e.g.::
345 345
346 # echo 0x301 >/proc/sys/kernel/real-root-dev 346 # echo 0x301 >/proc/sys/kernel/real-root-dev
347 347
348 Note that the mechanism is incompatible with N 348 Note that the mechanism is incompatible with NFS and similar file
349 systems. 349 systems.
350 350
351 This old, deprecated mechanism is commonly cal 351 This old, deprecated mechanism is commonly called ``change_root``, while
352 the new, supported mechanism is called ``pivot 352 the new, supported mechanism is called ``pivot_root``.
353 353
354 354
355 Mixed change_root and pivot_root mechanism 355 Mixed change_root and pivot_root mechanism
356 ------------------------------------------ 356 ------------------------------------------
357 357
358 In case you did not want to use ``root=/dev/ra 358 In case you did not want to use ``root=/dev/ram0`` to trigger the pivot_root
359 mechanism, you may create both ``/linuxrc`` an 359 mechanism, you may create both ``/linuxrc`` and ``/sbin/init`` in your initrd
360 image. 360 image.
361 361
362 ``/linuxrc`` would contain only the following: 362 ``/linuxrc`` would contain only the following::
363 363
364 #! /bin/sh 364 #! /bin/sh
365 mount -n -t proc proc /proc 365 mount -n -t proc proc /proc
366 echo 0x0100 >/proc/sys/kernel/real-roo 366 echo 0x0100 >/proc/sys/kernel/real-root-dev
367 umount -n /proc 367 umount -n /proc
368 368
369 Once linuxrc exited, the kernel would mount ag 369 Once linuxrc exited, the kernel would mount again your initrd as root,
370 this time executing ``/sbin/init``. Again, it 370 this time executing ``/sbin/init``. Again, it would be the duty of this init
371 to build the right environment (maybe using th 371 to build the right environment (maybe using the ``root= device`` passed on
372 the cmdline) before the final execution of the 372 the cmdline) before the final execution of the real ``/sbin/init``.
373 373
374 374
375 Resources 375 Resources
376 --------- 376 ---------
377 377
378 .. [#f1] Almesberger, Werner; "Booting Linux: 378 .. [#f1] Almesberger, Werner; "Booting Linux: The History and the Future"
379 https://www.almesberger.net/cv/papers/ols2 !! 379 http://www.almesberger.net/cv/papers/ols2k-9.ps.gz
380 .. [#f2] newlib package (experimental), with i 380 .. [#f2] newlib package (experimental), with initrd example
381 https://www.sourceware.org/newlib/ 381 https://www.sourceware.org/newlib/
382 .. [#f3] util-linux: Miscellaneous utilities f 382 .. [#f3] util-linux: Miscellaneous utilities for Linux
383 https://www.kernel.org/pub/linux/utils/uti 383 https://www.kernel.org/pub/linux/utils/util-linux/
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