What is GRUB & How is Works

GRUB :- GRand Unified Bootloader


GNU GRUB is a bootloader (can also be spelled boot loader) capable of loading a variety of free and proprietary operating systems. GRUB will work well with Linux, DOS, Windows, or BSD. GRUB stands for GRand Unified Bootloader.




GRUB is dynamically configurable. This means that the user can make changes during the boot time, which include altering existing boot entries, adding new, custom entries, selecting different kernels, or modifying initrd. GRUB also supports Logical Block Address mode. This means that if your computer has a fairly modern BIOS that can access more than 8GB (first 1024 cylinders) of hard disk space, GRUB will automatically be able to access all of it.



GRUB can be run from or be installed to any device (floppy disk, hard disk, CD-ROM, USB drive, network drive) and can load operating systems from just as many locations, including network drives. It can also decompress operating system images before booting them.

How does GRUB work?


When a computer boots, the BIOS transfers control to the first boot device, which can be a hard disk, a floppy disk, a CD-ROM, or any other BIOS-recognized device. We'll concentrate on hard disks, for the sake of simplicity.



The first sector on a hard is called the Master Boot Record (MBR). This sector is only 512 bytes long and contains a small piece of code (446 bytes) called the primary boot loader and the partition table (64 bytes) describing the primary and extended partitions.



By default, MBR code looks for the partition marked as active and once such a partition is found, it loads its boot sector into memory and passes control to it.



GRUB replaces the default MBR with its own code.



Furthermore, GRUB works in stages.



Stage 1 is located in the MBR and mainly points to Stage 2, since the MBR is too small to contain all of the needed data.



Stage 2 points to its configuration file, which contains all of the complex user interface and options we are normally familiar with when talking about GRUB. Stage 2 can be located anywhere on the disk. If Stage 2 cannot find its configuration table, GRUB will cease the boot sequence and present the user with a command line for manual configuration.



Stage 1.5 also exists and might be used if the boot information is small enough to fit in the area immediately after MBR.



The Stage architecture allows GRUB to be large (~20-30K) and therefore fairly complex and highly configurable, compared to most bootloaders, which are sparse and simple to fit within the limitations of the Partition Table.

GRUB :- GRand Unified Bootloader

GNU GRUB is a bootloader (can also be spelled boot loader) capable of loading a variety of free and proprietary operating systems. GRUB will work well with Linux, DOS, Windows, or BSD. GRUB stands for GRand Unified Bootloader.

GRUB is dynamically configurable. This means that the user can make changes during the boot time, which include altering existing boot entries, adding new, custom entries, selecting different kernels, or modifying initrd. GRUB also supports Logical Block Address mode. This means that if your computer has a fairly modern BIOS that can access more than 8GB (first 1024 cylinders) of hard disk space, GRUB will automatically be able to access all of it.

GRUB can be run from or be installed to any device (floppy disk, hard disk, CD-ROM, USB drive, network drive) and can load operating systems from just as many locations, including network drives. It can also decompress operating system images before booting them.



How does GRUB work?

When a computer boots, the BIOS transfers control to the first boot device, which can be a hard disk, a floppy disk, a CD-ROM, or any other BIOS-recognized device. We'll concentrate on hard disks, for the sake of simplicity.

The first sector on a hard is called the Master Boot Record (MBR). This sector is only 512 bytes long and contains a small piece of code (446 bytes) called the primary boot loader and the partition table (64 bytes) describing the primary and extended partitions.

By default, MBR code looks for the partition marked as active and once such a partition is found, it loads its boot sector into memory and passes control to it.

GRUB replaces the default MBR with its own code.

Furthermore, GRUB works in stages.

Stage 1 is located in the MBR and mainly points to Stage 2, since the MBR is too small to contain all of the needed data.

Stage 2 points to its configuration file, which contains all of the complex user interface and options we are normally familiar with when talking about GRUB. Stage 2 can be located anywhere on the disk. If Stage 2 cannot find its configuration table, GRUB will cease the boot sequence and present the user with a command line for manual configuration.

Stage 1.5 also exists and might be used if the boot information is small enough to fit in the area immediately after MBR.

The Stage architecture allows GRUB to be large (~20-30K) and therefore fairly complex and highly configurable, compared to most bootloaders, which are sparse and simple to fit within the limitations of the Partition Table.

GRUB :- GRand Unified Bootloader

GNU GRUB is a bootloader (can also be spelled boot loader) capable of loading a variety of free and proprietary operating systems. GRUB will work well with Linux, DOS, Windows, or BSD. GRUB stands for GRand Unified Bootloader.

GRUB is dynamically configurable. This means that the user can make changes during the boot time, which include altering existing boot entries, adding new, custom entries, selecting different kernels, or modifying initrd. GRUB also supports Logical Block Address mode. This means that if your computer has a fairly modern BIOS that can access more than 8GB (first 1024 cylinders) of hard disk space, GRUB will automatically be able to access all of it.

GRUB can be run from or be installed to any device (floppy disk, hard disk, CD-ROM, USB drive, network drive) and can load operating systems from just as many locations, including network drives. It can also decompress operating system images before booting them.



How does GRUB work?

When a computer boots, the BIOS transfers control to the first boot device, which can be a hard disk, a floppy disk, a CD-ROM, or any other BIOS-recognized device. We'll concentrate on hard disks, for the sake of simplicity.

The first sector on a hard is called the Master Boot Record (MBR). This sector is only 512 bytes long and contains a small piece of code (446 bytes) called the primary boot loader and the partition table (64 bytes) describing the primary and extended partitions.

By default, MBR code looks for the partition marked as active and once such a partition is found, it loads its boot sector into memory and passes control to it.

GRUB replaces the default MBR with its own code.

Furthermore, GRUB works in stages.

Stage 1 is located in the MBR and mainly points to Stage 2, since the MBR is too small to contain all of the needed data.

Stage 2 points to its configuration file, which contains all of the complex user interface and options we are normally familiar with when talking about GRUB. Stage 2 can be located anywhere on the disk. If Stage 2 cannot find its configuration table, GRUB will cease the boot sequence and present the user with a command line for manual configuration.

Stage 1.5 also exists and might be used if the boot information is small enough to fit in the area immediately after MBR.

The Stage architecture allows GRUB to be large (~20-30K) and therefore fairly complex and highly configurable, compared to most bootloaders, which are sparse and simple to fit within the limitations of the Partition Table.

How does GRUB work?


When a computer boots, the BIOS transfers control to the first boot device, which can be a hard disk, a floppy disk, a CD-ROM, or any other BIOS-recognized device. We'll concentrate on hard disks, for the sake of simplicity.



The first sector on a hard is called the Master Boot Record (MBR). This sector is only 512 bytes long and contains a small piece of code (446 bytes) called the primary boot loader and the partition table (64 bytes) describing the primary and extended partitions.



By default, MBR code looks for the partition marked as active and once such a partition is found, it loads its boot sector into memory and passes control to it.



GRUB replaces the default MBR with its own code.



Furthermore, GRUB works in stages.



Stage 1 is located in the MBR and mainly points to Stage 2, since the MBR is too small to contain all of the needed data.



Stage 2 points to its configuration file, which contains all of the complex user interface and options we are normally familiar with when talking about GRUB. Stage 2 can be located anywhere on the disk. If Stage 2 cannot find its configuration table, GRUB will cease the boot sequence and present the user with a command line for manual configuration.



Stage 1.5 also exists and might be used if the boot information is small enough to fit in the area immediately after MBR.



The Stage architecture allows GRUB to be large (~20-30K) and therefore fairly complex and highly configurable, compared to most bootloaders, which are sparse and simple to fit within the limitations of the Partition Table.

GRUB :- GRand Unified Bootloader

GNU GRUB is a bootloader (can also be spelled boot loader) capable of loading a variety of free and proprietary operating systems. GRUB will work well with Linux, DOS, Windows, or BSD. GRUB stands for GRand Unified Bootloader.

GRUB is dynamically configurable. This means that the user can make changes during the boot time, which include altering existing boot entries, adding new, custom entries, selecting different kernels, or modifying initrd. GRUB also supports Logical Block Address mode. This means that if your computer has a fairly modern BIOS that can access more than 8GB (first 1024 cylinders) of hard disk space, GRUB will automatically be able to access all of it.

GRUB can be run from or be installed to any device (floppy disk, hard disk, CD-ROM, USB drive, network drive) and can load operating systems from just as many locations, including network drives. It can also decompress operating system images before booting them.



How does GRUB work?

When a computer boots, the BIOS transfers control to the first boot device, which can be a hard disk, a floppy disk, a CD-ROM, or any other BIOS-recognized device. We'll concentrate on hard disks, for the sake of simplicity.

The first sector on a hard is called the Master Boot Record (MBR). This sector is only 512 bytes long and contains a small piece of code (446 bytes) called the primary boot loader and the partition table (64 bytes) describing the primary and extended partitions.

By default, MBR code looks for the partition marked as active and once such a partition is found, it loads its boot sector into memory and passes control to it.

GRUB replaces the default MBR with its own code.

Furthermore, GRUB works in stages.

Stage 1 is located in the MBR and mainly points to Stage 2, since the MBR is too small to contain all of the needed data.

Stage 2 points to its configuration file, which contains all of the complex user interface and options we are normally familiar with when talking about GRUB. Stage 2 can be located anywhere on the disk. If Stage 2 cannot find its configuration table, GRUB will cease the boot sequence and present the user with a command line for manual configuration.

Stage 1.5 also exists and might be used if the boot information is small enough to fit in the area immediately after MBR.

The Stage architecture allows GRUB to be large (~20-30K) and therefore fairly complex and highly configurable, compared to most bootloaders, which are sparse and simple to fit within the limitations of the Partition Table.

The remote session was disconnected because there are no remote desktop license servers available to provide a license

1.      Login to a server of same vlan.

2.      Click Start, point to Administrative Tools, point to Remote Desktop Services, and then click Remote Desktop Session Host Configuration.

 

3.      If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click yes. 

4.      Under Licensing, double-click Remote Desktop license servers. 

5.      In the Remote Desktop license servers area, click Add. 

6.      In the License sever name or IP address box, type the server name or IP address of the Remote Desktop license server. 

7.      Click OK, and then click OK again.

Verify

To verify that connections to the RD Session Host server are working properly, establish a remote session with the RD Session Host server.

How to create a datastore cluster in VMware

1.  Open vCenter and go to the Home tab.

2.  Click on the Datastores and Datastore Clusters option

3.  Right click on your Datacenter

*Note:  Datastore clusters cannot travers multiple datastores
4.  Select the New Datastore Cluster option from the pull-down menu

5.  A wizard will open.  Provide a name for your datastore cluster and make sure there is a check mark next to Turn on Storage DRS.

6.  Choose No Automation (Manual) or Fully Automated.

*I decided to use No Automation for now, at least in the testing phase.  No Automation makes recommendations to move virtual disks to other datastores that either have more space available and/or better I/O resources.  Fully Automated makes the changes automatically without getting administrator input.
7.  You can accept the defaults for the next couple steps of the wizard.

8.  When it’s time to select datastores, choose the datastores you’d like to put in this cluster.

Since we chose the No Automation method, we’ll need to check the recommendations SDRS has made manually.  To do this go to Home>>Datastores and Datastore Clusters.  Highlight the datastore cluster and then choose the Storage DRS tab.  All of the recommendations will be listed and selected by default.  You can click the Override Storage DRS Recommendations and select them individually if you so desire. Then click on Apply Recommendations and the appropriate tasks will execute.

This manual method, although safe, may go unnoticed by administrators.  To combat this, you might decide to create an alert notification that gets triggered whenever there is a Storage DRS alarm.  To set this up, highlight vCenter at the top of the tree on the left.  Click on the alarms tab, right-click the Storage DRS Recommendations and choose Edit Settings.  From this menu you can set it up to email you whenever this alarm is triggered.

There are many more details surrounding the implementation Storage DRS, but this brief overview is enough to set it up and start using it.  With alarm notifications you get the best of both worlds.  Using this strategy you won’t get caught off guard if SDRS tries to automatically storage vMotion a virtual machine using full automation, but you will be immediately notified of any recommended changes.