GRUB2 めも

ブートローダ

電源ON　→　BIOS　→　ブートローダ（GRUB2）

※昔、LILOブートローダでハマった記憶が（汗）　現在、GRUB2がスタンダードなのね。

grub2-mkconfig　→　grub.cfgを生成

# grep -w menuentry /etc/grub2.cfg
menuentry 'CentOS Linux (3.10.0-1127.13.1.el7.x86_64) 7 (Core)' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {
menuentry 'CentOS Linux (3.10.0-1127.13.1.el7.x86_64) 7 (Core) with debugging' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {
menuentry 'CentOS Linux 7 (Core), with Linux 3.10.0-229.el7.x86_64' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {
menuentry 'CentOS Linux 7 (Core), with Linux 0-rescue-fbf48c96b49c4cfca19cde302d4b2615' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-fbf48c96b49c4cfca19cde302d4b2615-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {

# cat /etc/grub2.cfg | less

### BEGIN /etc/grub.d/10_linux ###
menuentry 'CentOS Linux (3.10.0-1127.13.1.el7.x86_64) 7 (Core)' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb33
5' {
        load_video
        set gfxpayload=keep
        insmod gzio
        insmod part_msdos
        insmod xfs
        set root='hd0,msdos1'
        if [ x$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 --hint='hd0,msdos1'  8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        else
          search --no-floppy --fs-uuid --set=root 8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        fi
        linux16 /vmlinuz-3.10.0-1127.13.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet LANG=ja_JP.UTF-8
        initrd16 /initramfs-3.10.0-1127.13.1.el7.x86_64.img
}
menuentry 'CentOS Linux (3.10.0-1127.13.1.el7.x86_64) 7 (Core) with debugging' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b
3ce-d7aaa65eb335' {
        load_video
        set gfxpayload=keep
        insmod gzio
        insmod part_msdos
        insmod xfs
        set root='hd0,msdos1'
        if [ x$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 --hint='hd0,msdos1'  8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        else
          search --no-floppy --fs-uuid --set=root 8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        fi
        linux16 /vmlinuz-3.10.0-1127.13.1.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet LANG=ja_JP.UTF-8 systemd.log_level=debug systemd.log_target=kmsg
        initrd16 /initramfs-3.10.0-1127.13.1.el7.x86_64.img
}
menuentry 'CentOS Linux 7 (Core), with Linux 3.10.0-229.el7.x86_64' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-229.el7.x86_64-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {
        load_video
        set gfxpayload=keep
        insmod gzio
        insmod part_msdos
        insmod xfs
        set root='hd0,msdos1'
        if [ x$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 --hint='hd0,msdos1'  8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        else
          search --no-floppy --fs-uuid --set=root 8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        fi
        linux16 /vmlinuz-3.10.0-229.el7.x86_64 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet LANG=ja_JP.UTF-8
        initrd16 /initramfs-3.10.0-229.el7.x86_64.img
}
menuentry 'CentOS Linux 7 (Core), with Linux 0-rescue-fbf48c96b49c4cfca19cde302d4b2615' --class rhel fedora --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-fbf48c96b49c4cfca19cde302d4b2615-advanced-c416f0c2-5208-414b-b3ce-d7aaa65eb335' {
        load_video
        insmod gzio
        insmod part_msdos
        insmod xfs
        set root='hd0,msdos1'
        if [ x$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 --hint='hd0,msdos1'  8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        else
          search --no-floppy --fs-uuid --set=root 8b1d9da5-45ff-460c-8e59-014a2b3c9f9a
        fi
        linux16 /vmlinuz-0-rescue-fbf48c96b49c4cfca19cde302d4b2615 root=/dev/mapper/centos-root ro rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet
        initrd16 /initramfs-0-rescue-fbf48c96b49c4cfca19cde302d4b2615.img
}

/etc/default/grubは全体設定用のファイル

# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet"
GRUB_DISABLE_RECOVERY="true"

現在の起動メニューを確認する

# grub2-editenv list
saved_entry=CentOS Linux (3.10.0-1127.13.1.el7.x86_64) 7 (Core)