1 .\" Copyright (c) 2013 Marcel Moolenaar 2 .\" Copyright (c) 2013 Craig Rodrigues 3 .\" All rights reserved. 4 .\" 5 .\" Redistribution and use in source and binary forms, with or without 6 .\" modification, are permitted provided that the following conditions 7 .\" are met: 8 .\" 1. Redistributions of source code must retain the above copyright 9 .\" notice, this list of conditions and the following disclaimer. 10 .\" 2. Redistributions in binary form must reproduce the above copyright 11 .\" notice, this list of conditions and the following disclaimer in the 12 .\" documentation and/or other materials provided with the distribution. 13 .\" 14 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND 15 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE 18 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24 .\" SUCH DAMAGE. 25 .\" 26 .\" 27 .Dd October 17, 2013 28 .Dt MOUNT.CONF 5 29 .Os 30 .Sh NAME 31 .Nm mount.conf 32 .Nd root file system mount configuration file 33 .Sh SYNOPSIS 34 .Pa /.mount.conf 35 .Sh DESCRIPTION 36 During the bootup process, the 37 .Fx 38 kernel will try to mount the root file system 39 using the logic in the 40 .Fn vfs_mountroot 41 function in 42 .Pa src/sys/kern/vfs_mountroot.c . 43 The root mount logic can be described as follows: 44 .Bl -enum 45 .It 46 The kernel will synthesize in memory a config file 47 with default directives for mounting 48 the root file system. 49 The logic for this is in 50 .Fn vfs_mountroot_conf0 . 51 .It 52 The kernel will first mount 53 .Xr devfs 4 54 as the root file system. 55 .It 56 Next, the kernel will parse the in-memory config file created in step 1 57 and try to mount the actual root file system. 58 See 59 .Sx FILE FORMAT 60 for the format of the config file. 61 .It 62 When the actual root file system is mounted, 63 .Xr devfs 4 64 will be re-mounted on the 65 .Pa /dev 66 directory. 67 .It 68 If a 69 .Pa /.mount.conf 70 file does not exist in the root file system which was 71 just mounted, the root mount logic stops here. 72 .It 73 If a 74 .Pa /.mount.conf 75 file exists in the root file system which was just mounted, 76 this file will be parsed, and the kernel will use this new config 77 file to try to re-mount the root file system. 78 See 79 .Sx FILE FORMAT 80 for the format of the config file. 81 .It 82 If the new root file system has a 83 .Pa /.mount 84 directory, the old root file system will be re-mounted 85 on 86 .Pa /.mount . 87 .It 88 The root mount logic will go back to step 4. 89 .El 90 .Pp 91 The root mount logic is recursive, and step 8 will 92 be repeated as long as each new root file system 93 which is mounted has a 94 .Pa /.mount.conf 95 file. 96 .Sh FILE FORMAT 97 The kernel parses each line in 98 .Pa .mount.conf 99 and then tries to perform the action specified on that line as soon as it is parsed. 100 .Bl -tag -width "XXXXXXXXXX" 101 .It Ic # 102 A line beginning with a # is a comment and is ignored. 103 .It Ic {FS}:{MOUNTPOINT} {OPTIONS} 104 The kernel will try to mount this in an 105 operation equivalent to: 106 .Bd -literal -offset indent 107 mount -t {FS} -o {OPTIONS} {MOUNTPOINT} / 108 .Ed 109 .Pp 110 If this is successfully mounted, 111 further lines in 112 .Pa .mount.conf 113 are ignored. 114 If all lines in 115 .Pa .mount.conf 116 have been processed and no root file system has been successfully 117 mounted, then the action specified by 118 .Ic .onfail 119 is performed. 120 .It Ic .ask 121 When the kernel processes this line, a 122 .Li mountroot> 123 command-line prompt is displayed. 124 At this prompt, the operator can enter the root mount. 125 .It Ic .md Ar file 126 Create a memory backed 127 .Xr md 4 128 virtual disk, using 129 .Ar file 130 as the backing store. 131 .It Ic .onfail Ar [panic|reboot|retry|continue] 132 If after parsing all the lines in 133 .Pa .mount.conf 134 the kernel is unable to mount a root file system, 135 the 136 .Ic .onfail 137 directive tells the kernel what action to perform. 138 .It Ic .timeout Ar N 139 Before trying to mount a root file system, 140 if the root mount device does not exist, wait at most 141 .Ar N 142 seconds for the device to appear before trying to mount it. 143 If 144 .Ic .timeout 145 is not specified, the default timeout is 3 seconds. 146 .El 147 .Sh EXAMPLES 148 The following example 149 .Pa .mount.conf 150 will direct the kernel to try mounting the root file system 151 first as an ISO CD9660 file system on 152 .Pa /dev/cd0 , 153 then if that does not work, as an ISO CD9660 file system on 154 .Pa /dev/cd1 , 155 and then if that does not work, as a UFS file system on 156 .Pa /dev/ada0s1a . 157 If that does not work, a 158 .Li mountroot> 159 command-line prompt will be displayed where the operator 160 can manually enter the root file system to mount. 161 Finally if that does not work, the kernel will panic. 162 .Bd -literal -offset indent 163 .Li .onfail panic 164 .Li .timeout 3 165 cd9660:/dev/cd0 ro 166 .Li .timeout 0 167 cd9660:/dev/cd1 ro 168 .Li .timeout 3 169 ufs:/dev/ada0s1a 170 .Li .ask 171 .Ed 172 .Pp 173 The following example 174 .Pa .mount.conf 175 will direct the kernel to create a 176 .Xr md 4 177 memory disk attached to the file 178 .Pa /data/OS-1.0.iso 179 and then mount the ISO CD9660 file system 180 on the md device which was just created. 181 The last line is a comment which is ignored. 182 .Bd -literal -offset indent 183 .Li .timeout 3 184 .Li .md /data/OS-1.0.iso 185 .Li cd9600:/dev/md# ro 186 .Li # Can also use cd9660:/dev/md0 ro 187 .Ed 188 .Pp 189 The following example 190 .Pa .mount.conf 191 will direct the kernel to create a 192 .Xr md 4 193 memory disk attached to the file 194 .Pa /data/base.ufs.uzip 195 and then mount the UFS file system 196 on the md uzip device which was just created 197 by the 198 .Xr geom_uzip 4 199 driver. 200 .Bd -literal -offset indent 201 .Li .md /data/base.ufs.uzip 202 .Li ufs:/dev/md#.uzip ro 203 .Li # Can also use ufs:/dev/md0.uzip ro 204 .Ed 205 .Pp 206 The following example 207 .Pa .mount.conf 208 will direct the kernel to do a unionfs 209 mount on a directory 210 .Pa /jail/freebsd-8-stable 211 which has a 212 .Xr chroot 2 213 environment. 214 .Bd -literal -offset indent 215 .Li .timeout 3 216 .Li unionfs:/jail/freebsd-8-stable 217 .Ed 218 .Sh NOTES 219 For each root file system which is mounted, a 220 .Pa /dev 221 directory 222 .Em must 223 exist so that the root mount logic can properly re-mount 224 .Xr devfs 4 . 225 If this directory does not exist, the system 226 may hang during the bootup process. 227 .Sh SEE ALSO 228 .Xr nmount 2 , 229 .Xr md 4 , 230 .Xr boot.config 5 , 231 .Xr fstab 5 , 232 .Xr boot 8 , 233 .Xr loader 8 , 234 .Xr mount 8 235 .Sh HISTORY 236 The 237 .Nm 238 file first appeared in 239 .Fx 9.0 . 240 .Sh AUTHORS 241 .An -nosplit 242 The root mount logic in the 243 .Fx 244 kernel which parses 245 .Pa /.mount.conf 246 was written by 247 .An Marcel Moolenaar Aq Mt marcel@FreeBSD.org . 248 This man page was written by 249 .An Craig Rodrigues Aq Mt rodrigc@FreeBSD.org . 250