99 lines
2.0 KiB
Markdown
99 lines
2.0 KiB
Markdown
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# Basic Startup
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BIOS > MBR > GRUB > Kernel > Init > Run Level
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- The BIOS identifies system hardware.
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- The Master Boot Record contains partition and filesystem data.
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- The Grand Unified Bootloader executes the kernel.
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- The Init Executes designates run level (via SysVinit, Upstart, or Systemd).
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- Run Level starts the user's session.
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The Master Boot Record is a 512 byte file called boot.img which starts the first sectore of core.img into memory (GRUB Stage 1.5), which then executes /boot/grub.
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# Access system
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Ctrl+c at boot then add in
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> rw init=bash
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# Run Levels
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0: Half
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1: Single user mode
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2: Multi-user, without NFS
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3: Full multi-user mode
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4: Unused
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5: X11
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6: Reboot
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None of this is used by humans anymore - it's all systemd.
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# Systemd
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See what's running with ....
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> systemctl list-units
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Stop, start, whatever with:
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systemctl enable|stop|start httpd
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This starts httpd (Fedora's word for Apache2).
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# Boot Records
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'File System Tab' under /etc/fstab keeps track of the partitions and boot order.
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The logical voluem manager (LVM) can make non-hardware partitions.
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The nomenclature is:
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- PV = physical volume
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- LV = logical volume
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- VG = volume group
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# Volume Groups
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> sudo vgcreate work-volume /dev/sdb2 /dev/sdb4
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This creates the volume group 'work-volume', consisting in sdb2 and sdb4.
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Now you ahve a volume group, you can use it as part of a new logical volume.
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> sudo lvcreate -n noob-lv work-volume
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Then scan for all logical volumes on the system with lvscan.
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> sudo lvscan
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# GRUB
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Install a grub with either:
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> sudo grub-install /dev/sda
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or
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> sudo grub2-install /dev/sda
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This takes all settings from /etc/fstab.
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Then when done editing settings update the script in /boot/grub/grub.cfg (in Debian) or /boot/boot/grub/menu (in other systems).
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There are default examples in /etc/grub.d/ (but not on Ubuntu).
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Finalize your settings with grub-mkconfig (or grub2-mkconfig), or update-grub.
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# Cowardice
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If you can't do that, use boot-repair:
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> help.ubuntu.com/community/Boot-Repair
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