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grub2配置
环境：ubuntu14.04
默认配置文件路径/etc/default/grub
例子：
GRUB_DEFAULT=0 #默认启动那一个 #GRUB_HIDDEN_TIMEOUT=15 #选择菜单是否隐藏，注释掉就直接显示了 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX=""
更新grup调用
ubuntu@ubuntu-Lenovo-Product:~$ sudo update-grub Generating grub configuration file ... Found linux image: /boot/vmlinuz-3.16.0-031600-generic Found initrd image: /boot/initrd.img-3.16.0-031600-generic Found linux image: /boot/vmlinuz-3.13.0-43-generic Found initrd image: /boot/initrd.img-3.13.0-43-generic Found linux image: /boot/vmlinuz-3.13.0-41-generic Found initrd image: /boot/initrd.img-3.13.0-41-generic Found linux image: /boot/vmlinuz-3.13.0-24-generic Found initrd image: /boot/initrd.img-3.13.0-24-generic Found memtest86+ image: /boot/memtest86+.elf Found memtest86+ image: /boot/memtest86+.bin done
然后如上所示update-grup会在系统里找编译好的内核，试过放在根目录/也能找到。
update-grup找完内核后，开始更新文件/boot/grub/grub.cfg
这个文件里有开机启动菜单入口信息，如下：
menuentry ‘Ubuntu‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-simple-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
linux /boot/vmlinuz-3.16.0-031600-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro quiet splash $vt_handoff
initrd /boot/initrd.img-3.16.0-031600-generic
}
submenu ‘Advanced options for Ubuntu‘ $menuentry_id_option ‘gnulinux-advanced-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
menuentry ‘Ubuntu, with Linux 3.16.0-031600-generic‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.16.0-031600-generic-advanced-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.16.0-031600-generic ...‘
linux /boot/vmlinuz-3.16.0-031600-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro quiet splash $vt_handoff
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.16.0-031600-generic
}
menuentry ‘Ubuntu, with Linux 3.16.0-031600-generic (recovery mode)‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.16.0-031600-generic-recovery-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.16.0-031600-generic ...‘
linux /boot/vmlinuz-3.16.0-031600-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro recovery nomodeset
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.16.0-031600-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-43-generic‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-43-generic-advanced-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-43-generic ...‘
linux /boot/vmlinuz-3.13.0-43-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro quiet splash $vt_handoff
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-43-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-43-generic (recovery mode)‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-43-generic-recovery-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-43-generic ...‘
linux /boot/vmlinuz-3.13.0-43-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro recovery nomodeset
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-43-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-41-generic‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-41-generic-advanced-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-41-generic ...‘
linux /boot/vmlinuz-3.13.0-41-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro quiet splash $vt_handoff
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-41-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-41-generic (recovery mode)‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-41-generic-recovery-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-41-generic ...‘
linux /boot/vmlinuz-3.13.0-41-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro recovery nomodeset
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-41-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-24-generic‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-24-generic-advanced-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
gfxmode $linux_gfx_mode
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-24-generic ...‘
linux /boot/vmlinuz-3.13.0-24-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro quiet splash $vt_handoff
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-24-generic
}
menuentry ‘Ubuntu, with Linux 3.13.0-24-generic (recovery mode)‘ --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option ‘gnulinux-3.13.0-24-generic-recovery-e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668‘ {
recordfail
load_video
insmod gzio
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
echo ‘Loading Linux 3.13.0-24-generic ...‘
linux /boot/vmlinuz-3.13.0-24-generic root=UUID=e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668 ro recovery nomodeset
echo ‘Loading initial ramdisk ...‘
initrd /boot/initrd.img-3.13.0-24-generic
}
}
### END /etc/grub.d/10_linux ###
### BEGIN /etc/grub.d/20_linux_xen ###
### END /etc/grub.d/20_linux_xen ###
### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry ‘Memory test (memtest86+)‘ {
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
knetbsd /boot/memtest86+.elf
}
menuentry ‘Memory test (memtest86+, serial console 115200)‘ {
insmod part_msdos
insmod ext2
set root=‘hd0,msdos1‘
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
else
search --no-floppy --fs-uuid --set=root e96bea5c-cd18-4b7d-b4a6-1f7ad59b6668
fi
linux16 /boot/memtest86+.bin console=ttyS0,115200n8
}
可以看到地一个menuentry有submenu ‘Advanced options for Ubuntu‘，submenu里边嵌套menuentry（结构一样）
之前提到的配置文件/etc/default/grub的DEFAULT_ENTRY指的是第一层的menuentry而不是submenu的。在上面的例子如果DEFAULT_ENTRY=1就表示默认启动menuentry ‘Memory test (memtest86+)。
在submenu里看到有很多不同内核，update-grub会选能检测到的版本最新的内核作为默认启动项目，如果要换内核启动可以：
开机时手工选择submenu的启动项。
让update-grub选择为默认内核，可以把不用的高版本内核备份起来（update-grub搜索的时候就找不到该内核），或者可能有命令选择内核（暂时没找到）。
grub2配置
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