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32 .Nd GPT bootcode for UFS on BIOS-based computers
35 is used on BIOS-based computers to boot from a UFS partition on a
45 first reads the GPT and determines which drive and partition to
46 boot from, as described under
49 If it does not find an eligible partition, or if the user hits a
50 key within three seconds,
52 switches from auto-boot to interactive mode.
53 Interactive mode allows manual selection of the disk, partition,
54 filename, and boot option flags, as described in
56 .Sh IMPLEMENTATION NOTES
57 The GPT standard allows a variable number of partitions, but
59 only boots from tables with 128 partitions or less.
60 .Sh PARTITION ATTRIBUTES
62 checks and manages several attributes of GPT UFS partitions.
63 .Bl -tag -width ".Cm bootfailed"
65 Attempt to boot from this partition.
66 If more than one partition has the
70 will attempt to boot each one until successful.
72 Attempt to boot from this partition only one time.
73 Setting this attribute with
75 automatically also sets the
78 Multiple partitions may have the
86 attribute marks partitions that had the
88 attribute set, but failed to boot.
89 This attribute is managed by the system.
93 .Sx "POST-BOOT ACTIONS"
97 For normal usage, the user does not have to set or manage any of the
100 will boot from the first UFS partition found.
104 attribute can be used for testing an upgraded operating system on
105 an already-working computer.
106 The existing system partition is left untouched, and the new version
107 of the operating system to be tested is installed on another partition.
110 attribute is set on that new test partition.
111 The next boot is attempted from the test partition.
112 Success or failure will be shown in the system log files.
113 After a successful boot of the test partition, a user script can check
114 the logs and change the
116 attributes so the test partition becomes the new system partition.
119 attribute is cleared after an attempted boot, a failed boot will not
120 leave the system attempting to boot from a partition that will never
122 Instead, the system will boot from the older, known-working operating
123 system that has not been modified.
126 attribute is set on any partitions, booting will be attempted from them
128 If no partitions with
130 attributes are found, booting will be attempted from the first UFS
134 first reads the partition table.
137 partitions with only the
139 attribute set, indicating a failed boot, are set to
142 then scans through all of the
145 Boot behavior depends on the combination of
149 attributes set on those partitions.
150 .Bl -tag -width ".Cm bootonce + .Cm bootme"
151 .It Cm bootonce + Cm bootme
152 Highest priority: booting is attempted from each of the
154 partitions with both of these attributes.
155 On each partition, the
157 attribute is removed and the boot attempted.
159 Middle priority: booting is attempted from each of the
170 attributes are found on any partitions, booting is attempted from the
173 partition on the disk.
174 .Sh POST-BOOT ACTIONS
176 .Pa /etc/rc.d/gptboot
177 checks the attributes of
179 partitions on all GPT disks.
183 .Dq boot from X failed
185 Partitions with only the
187 attribute, indicating a partition that successfully booted, generate a
188 .Dq boot from X succeeded
192 attributes are cleared from all the partitions.
195 attribute is cleared from the partition that successfully booted.
196 There is normally only one of these.
198 .Bl -tag -width /boot/gptboot -compact
202 parameters for the boot blocks
209 partition, usually the first partition on the disk.
216 is typically installed in combination with
224 .Bd -literal -offset indent
225 gpart bootcode -b /boot/pmbr -p /boot/gptboot -i 1 ada0
229 can also be installed without the PMBR:
230 .Bd -literal -offset indent
231 gpart bootcode -p /boot/gptboot -i 1 ada0
236 attribute for partition 2:
237 .Bd -literal -offset indent
238 gpart set -a bootme -i 2 ada0
243 attribute for partition 2, automatically also setting the
246 .Bd -literal -offset indent
247 gpart set -a bootonce -i 2 ada0
256 appeared in FreeBSD 7.1.
258 This manual page written by
259 .An Warren Block Aq wblock@FreeBSD.org .