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2 .\" Copyright (c) 2013 Craig Rodrigues
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34 .Nd root file system mount configuration file
38 During the bootup process, the
40 kernel will try to mount the root file system
41 using the logic in the
44 .Pa src/sys/kern/vfs_mountroot.c .
45 The root mount logic can be described as follows:
48 The kernel will synthesize in memory a config file
49 with default directives for mounting
51 The logic for this is in
52 .Fn vfs_mountroot_conf0 .
54 The kernel will first mount
56 as the root file system.
58 Next, the kernel will parse the in-memory config file created in step 1
59 and try to mount the actual root file system.
62 for the format of the config file.
64 When the actual root file system is mounted,
66 will be re-mounted on the
72 file does not exist in the root file system which was
73 just mounted, the root mount logic stops here.
77 file exists in the root file system which was just mounted,
78 this file will be parsed, and the kernel will use this new config
79 file to try to re-mount the root file system.
82 for the format of the config file.
84 If the new root file system has a
86 directory, the old root file system will be re-mounted
90 The root mount logic will go back to step 4.
93 The root mount logic is recursive, and step 8 will
94 be repeated as long as each new root file system
95 which is mounted has a
99 The kernel parses each line in
101 and then tries to perform the action specified on that line as soon as it is parsed.
102 .Bl -tag -width "XXXXXXXXXX"
104 A line beginning with a # is a comment and is ignored.
105 .It Ic {FS}:{MOUNTPOINT} {OPTIONS}
106 The kernel will try to mount this in an
107 operation equivalent to:
108 .Bd -literal -offset indent
109 mount -t {FS} -o {OPTIONS} {MOUNTPOINT} /
112 If this is successfully mounted,
118 have been processed and no root file system has been successfully
119 mounted, then the action specified by
123 When the kernel processes this line, a
125 command-line prompt is displayed.
126 At this prompt, the operator can enter the
129 Create a memory backed
133 as the backing store.
134 .It Ic .onfail Ar [panic|reboot|retry|continue]
135 If after parsing all the lines in
137 the kernel is unable to mount a root file system,
140 directive tells the kernel what action to perform.
142 Before trying to mount a root file system,
143 if the root mount device does not exist, wait at most
145 seconds for the device to appear before trying to mount it.
148 is not specified, the default timeout is 3 seconds.
151 The following example
153 will direct the kernel to try mounting the root file system
154 first as an ISO CD9660 file system on
156 then if that does not work, as an ISO CD9660 file system on
158 and then if that does not work, as a UFS file system on
160 If that does not work, a
162 command-line prompt will be displayed where the operator
163 can manually enter the root file system to mount.
164 Finally if that does not work, the kernel will panic.
165 .Bd -literal -offset indent
176 The following example
178 will direct the kernel to create a
180 memory disk attached to the file
182 and then mount the ISO CD9660 file system
183 on the md device which was just created.
184 The last line is a comment which is ignored.
185 .Bd -literal -offset indent
187 .Li .md /data/OS-1.0.iso
188 .Li cd9600:/dev/md# ro
189 .Li # Can also use cd9660:/dev/md0 ro
192 The following example
194 will direct the kernel to create a
196 memory disk attached to the file
197 .Pa /data/base.ufs.uzip
198 and then mount the UFS file system
199 on the md uzip device which was just created
203 .Bd -literal -offset indent
204 .Li .md /data/base.ufs.uzip
205 .Li ufs:/dev/md#.uzip ro
206 .Li # Can also use ufs:/dev/md0.uzip ro
209 The following example
211 will direct the kernel to do a unionfs
213 .Pa /jail/freebsd-8-stable
217 .Bd -literal -offset indent
219 .Li unionfs:/jail/freebsd-8-stable
222 For each root file system which is mounted, a
226 exist so that the root mount logic can properly re-mount
228 If this directory does not exist, the system
229 may hang during the bootup process.
241 file first appeared in
245 The root mount logic in the
250 .An Marcel Moolenaar Aq marcel@FreeBSD.org .
251 This man page was written by
252 .An Craig Rodrigues Aq rodrigc@FreeBSD.org .