The partition that contains the windows os files is known as the what type of partition?

Inactive

You use the Inactive command on MBR partitions to mark a system or boot partition as active. When the partition is marked inactive, the system BIOS looks for the next configured drive, such as a CD-ROM drive, to boot the system when it is restarted. The syntax of this command is:

Warning

Do not use the Inactive command on any system or boot partition if you do not have good knowledge of the Windows XP or Windows Server 2003 operating systems, as this may make your computer unable to start. A computer cannot start without an active partition. Systems administrators can use this command to boot a computer from the network using PXE-compliant network adapters for Remote Installation Service (RIS).

If you make a system or boot partition inactive by mistake, you can use the Windows Setup CD-ROM to start the system using the Recovery Console. Once you are in the Recovery Console, you can use the Fixmbr and Fixboot commands to repair the inactive partition.

System and Boot Partitions

When a partition is created, it can be designated as the boot partition, system partition, or both. A system partition stores files that are used to boot (start) the computer. These are used whenever a computer is powered on (cold boot) or restarted from within the operating system (warm boot). A boot partition is a volume of the computer that contains the system files used to start the operating system. Once the boot files on the system partition have been accessed and have started the computer, the system files on the boot partition are accessed to start the operating system. The system partition is where the operating system is installed. The system and boot partitions can exist as separate partitions on the same computer, or on separate volumes.

The Root File System Image

Even though we will be mounting the root file system over NFS, you will need to load an image file to the eMMC in order to create a boot partition. But first you need to load the image file to a microSD card. A 4 GB card is sufficient. You should use a USB card reader, as there have been reports that the built-in readers on some laptops are not reliable under Linux. The card should show up as /dev/sdb. If not, you can execute:

dmesg | tail

just after inserting the card, and it should show what device was just recognized.

Browse to debian.beagleboard.org/images and download BBB-eMMC-flasher-debian-7.4-2014-04-14-2gb.img.xz. Uncompress the file with the xz command thus:

xz –d BBB-eMMC-flasher-debian-7.4-2014-03-26-2gb.img.xz

This yields one file, BBB-eMMC-flasher-debian-7.4-2014-03-26-2gb.img. Write this file to the microSD card with the dd command:

dd if=BBB-eMMC-flasher-debian-7.4-2014-03-26-2gb.img of=/dev/sdb

This will take a fairly long time. When it is finished, there will be two partitions on /dev/sdb; a bootable FAT partition named BEAGLEBONE, and an ext4 partition named eMMC-Flasher. This image is specifically for flashing the eMMC.

Insert the microSD into your unpowered BBB. The BBB documentation says that to boot from the microSD card, you must hold down the boot pushbutton while applying power. In my case, the mere presence of a microSD card causes the board to boot from the card. Power it up. The kernel will boot up as normal, and present a login prompt. But the pattern of the LEDs indicates that something else is going on. That something else is flashing the eMMC. When the four LEDs come on steady, the flashing is finished. Power down the board, remove the microSD card and repower the board. It boots Debian 7.4 from the eMMC.

Finally, you need to get the target root file system on to your workstation under your home directory. You do not want to copy it from the microSD card, because that image is specifically intended for flashing the eMMC. What you can do is copy from the BBB eMMC over the network to your workstation. Create a subdirectory under your home directory to match what you specified for rootpath in uEnvnet.txt. Now copy the entire target file system into that directory. I suggest copying each top level directory separately, rather than everything in one big cp –r command. Note, incidentally, that there are several top level directories that are empty. You can just execute a mkdir command for these. A few directories require some special attention:

/boot – Do not copy the /uboot directory. Just create an empty directory.

/dev – You only want the part of /dev that is on the microSD card. The remainder of /dev is populated by a program called udev.

/home – Do not copy your home directory that you mounted over NFS.

You will need to edit /etc/fstab as root user. There will be a line that looks something like this:

UUID=3bb11f04-4b37-49fd-a118-f1a7c1c4cfd7 / ext4 noatime,errors=remount-ro 0 1

Your UUID will probably be different. This line is trying to mount the root file system from a disk drive, which not surprisingly interferes with mounting over NFS. Just comment the line out and save the file.

Discover Hidden Partitions

Hard disk partitions can be hidden. Most Windows® machines contain at least one hidden partition used at startup. Most 64-bit versions of Windows® show a hidden boot partition labeled System Reserve. In order to discover whether a particular hard disk or USB stick contains hidden partitions we can do the following:

Go to Control Panel ≫ ≫ Administrative Tools ≫ Computer Management. Then click on Disk Management in the left pane (see Fig. 6.65).

From Fig. 6.65 we can see that we have two disks attached to the running computer. On one hand, the first disk (labeled Disk 0) has one hidden partition created by Windows® called System Reserved that is 350 MB in size. On the other hand, the second disk (labeled Disk 1) has one hidden partition without a label that is 1.12 GB in size.

In order to open the system reserved hidden partition through Windows File Explorer, you can download a free portable utility that works on Windows® 7 and above (Enterprise, Ultimate, and Professional) called OpenHiddenSystemDrive. You can download this utility from http://www.coderforlife.com/projects/win7boot/extras/#OpenHiddenSystemDrive.

Double-click on the OpenHiddenSystemDrive.exe file to open the hidden System Reserved partition in Windows Explorer. Once the partition opens, it may look empty, but this is just because everything is well hidden. You must show hidden and protected system files to see them by going to Control Panel ≫ Folder Options ≫ View tab. You then select the option Show hidden files, folders and drives. You also need to uncheck the box beside the option Hide Protected operating system files (Recommended). This will make all drive contents appear (see Fig. 6.66).

Another method to check for hidden partitions under Windows® is by using the DiskPart command line utility, which comes as a part of the Microsoft Windows® family (Windows® 8, 8.1, 7, Vista, XP, and Server 2003®).

To launch this tool, open a DOS prompt, type DiskPart and press Enter. Type the following to check of hidden partitions:

Type List disk to view a list of connected hard disks to this PC and associated numbers.

In order to view the partition of each disk you first need to select it through the select disk = n command, where n points to the disk number that appears in the first command.

After selecting the disk, we type list partition to see a list of partitions that exist within this disk.

Fig. 6.67 shows you a complete demonstration of these steps.

In order to access any hidden partition (especially the one hidden inside the USB drive as we demonstrated in Chapter 4), you can use a free tool to check and investigate such drives.

MiniTool Partition Wizard Free Edition allows you to uncover hidden partitions and access them. Follow these steps to achieve this:

Download and install MiniTool Partition Wizard from http://www.partitionwizard.com/free-partition-manager.html and then install the software using its simple steps.

After you launch the program you will notice that all hidden partitions inside disk drives attached to this machine will appear. Hidden partitions will have an asterisk (∗) at the front of their names. Right-click any hidden partition and select Explore to check its contents (see Fig. 6.68).

Setting Up Linux

We started with a Dell GX270 with 1.5 gigabytes of RAM and a 40 GB IDE HDD. We downloaded the Live DVD version of Ubuntu v7.10 (Gutsy Gibbon) from the Ubuntu Web site. The link to this ISO is http://releases.ubuntu.com/7.10/ubuntu-7.10-desktop-i386.iso.

We set up Ubuntu using the default settings. When we got to the partitioner we selected manual setup.4 We chose to use a 3 partition scheme, creating the partitions with the following parameters:

Boot Partition (must be established in the first 1024 tracks, usually within first 8G):

Mount point: /boot

Size: 128 megabytes

File System: ext2

Swap Partition:

Mount point: N/A

Size: 2000 megabytes

File System: swap

Root Partition

Mount point: /

Size: whatever space is left

File System: ext3

After the setup is complete we installed all the updates to Ubuntu 7.10. After restarting and logging in to Ubuntu for the first time, we fired up Firefox and went to the Ubuntu community forums to get the documentation to change the unsafe default settings in Ubuntu. The page is https://help.ubuntu.com/community/UnsafeDefaults.

There is also a change to make in /etc/init.d/mountdevsubfs.sh:

Open a terminal window located in the launch bar under Applications/Assessories.

Type the following line into the terminal window:

gksudo gedit /etc/init.d/mountdevsubfs.sh

and press Enter.

Enter your password.

Remove comments (#) from the following four lines starting with mkdir -p /dev/bus/usb/.usbfs line.

# Magic to make /proc/bus/usb work

#

mkdir -p /dev/bus/usb/.usbfs

domount usbfs “” /dev/bus/usb/.usbfs -obusmode=0700,devmode=0600, listmode=0644

ln -s .usbfs/devices /dev/bus/usb/devices

mount --rbind /dev/bus/usb /proc/bus/usb

Save the file, then restart the computer.

Next we need to set up an instance of VMware.

VII.B Hiding Places

Consider the common boot sector. To the vast majority of users, the fact that a program can be located at a physical position on the disk but not be referenced by the file directory list is a foreign concept. This confusion may contribute to the enormous success of boot sector viral programs.

The sector and even the partition boot record on a hard disk are accessible to dedicated amateurs armed with utility software. However, there are other places to hide on a disk that are not as easily examined. It is quite possible to format an additional track outside the normal range. To avoid problems between drives with variations in tolerance, the software does not “push” the limits of the hardware. Special programs for the Apple II computer provided 38 tracks rather than the normal 35. Various programs are available for MS-DOS as well that provide greater storage on the same-sized disks.

In addition to tracks outside of and between normal formats, there is substantial space between the sectors on a disk. Some programs can increase the number of sectors so as to increase the space on disk. However, it is also possible to use the additional space without formatting additional sectors, simply by writing information to the space between. This fact has occasionally been used by commercial software manufacturers for the purposes of copy protection.

9.1.2.2 Amazon elastic block store

The Amazon Elastic Block Store (EBS) allows AWS users to provide EC2 instances with persistent storage in the form of volumes that can be mounted at instance startup. They accommodate up to 1 TB of space and are accessed through a block device interface, thus allowing users to format them according to the needs of the instance they are connected to (raw storage, file system, or other). The content of an EBS volume survives the instance life cycle and is persisted into S3. EBS volumes can be cloned, used as boot partitions, and constitute durable storage since they rely on S3 and it is possible to take incremental snapshots of their content.

EBS volumes normally reside within the same availability zone of the EC2 instances that will use them to maximize the I/O performance. It is also possible to connect volumes located in different availability zones. Once mounted as volumes, their content is lazily loaded in the background and according to the request made by the operating system. This reduces the number of I/O requests that go to the network. Volume images cannot be shared among instances, but multiple (separate) active volumes can be created from them. In addition, it is possible to attach multiple volumes to a single instance or create a volume from a given snapshot and modify its size, if the formatted file system allows such an operation.

The expense related to a volume comprises the cost generated by the amount of storage occupied in S3 and by the number of I/O requests performed against the volume. Currently, Amazon charges $0.10/GB/month of allocated storage and $0.10 per 1 million requests made to the volume.

4 CLUSTER PERFORMANCE ISSUES CONCERNING DUAL BOOT IMPLICATION

The creation of a Linux computational facility from resources intended for a different daily purpose using Windows NT was easily achieved through the use of dual boot. Several issues were highlighted while implementing CFD problems using this strategy.

The dual boot feature poses an immediate barrier in gaining access to the computational resource when it is booted into the wrong operating system. Where the intention is to use the resource primarily for overnight computation, the individual processors can be configured to automatically reboot into the default Linux boot partition, at a designated time, which is the case used for this work. This strategy although very simple to implement, can cause problems both to NT users wishing to work during such times and computational resource users requiring access to Linux processors during the daytime. In this implementation, a small cluster of processors resides in a separate room to the rest of the processors. These processors reboot into Linux at a designated time, without causing significant disruption to users who are made aware in advance of this feature.

The second problem regarding the robust use of the facility for larger distributed processing using MPI, is when a processor is manually rebooted during computation. Without controlled management, such a reboot will cause the entire MPI process to crash on all associated processors losing all data. While this problem is unavoidable since the primary use of the cluster is for NT based activities. The devastation of such an activity has been limited through encouragement of regular checkpointing of program data with a small associated computational cost as illustrated in Figure 3. Additionally, rebooting through the action of pressing CTRL-ALT-DEL on the keyboard has been trapped on all processors, sending an appropriate signal to all residing programs. This signal is trapped in both the GA and Euler solver, and activates a final checkpointing procedure before a controlled exit of the program on all associated processors. A restart script residing on the master processor reestablishes a new set of available processors and attempts to continue the distributed computational job.

Some configuration time was required to establish the various processors required to increase the robustness and usability of the cluster when using a dual boot feature, however the process was straight forward and leads to substantial gains in the overall performance of the facility.

Deleted Partition Recovery Tools

When a partition is deleted, its entry in the partition table is removed. Although it can appear quite imposing that an entire partition of information is no longer visible, the data hasn't been destroyed from the disk. Essentially, deleting the partition is similar to removing the table of contents from a book; none of the information outside the table is missing, it just requires other methods to find it. This is where partition recovery tools come into play.

Partition recovery tools perform a number of automated tasks that will attempt to restore a damaged or deleted partition, and/or restore data from that partition. Some of the automated tasks these tools will use to locate and recover data include:

Determining the error on the disk, and allowing the user to choose another partition and make it active.

Scanning the disk space for a partition boot sector or damaged partition information, and then attempting to reconstruct the partition table entry. By finding the partition boot sector, it will have all the information necessary to reconstruct the entry in the partition table. Because both NTFS and FAT32 volumes maintain backup boot sectors, you can recover the volume by restoring the boot sector.

Scanning the disk space for a partition boot sector or data from deleted partition information, and then attempting to reconstruct the partition table entry.

A number of tools are available for partition recovery, each of which has various features that can make it easier to restore data that may have been lost from accidental deletion or damage to the partition. Damaged partitions can occur from power or software failure, a root directory being damaged by a virus, formatting, and being deleted with tools such as FDISK, DISKPART, or the Disk Management tool in the Computer Management console. Problems can also occur when the partition table, MFT, root directory, or boot record is lost or corrupt. Each of these can cause Windows not to recognize the hard disk, requiring partition recovery tools to be used to recover the partition and data.

Partitions

Partitioning is the allocation of electronic storage space within a storage device into separate data areas for a specific filesystem type. Whether implemented either via a partition editor tool or via the fdisk command, partitions can be created, deleted, or modified. The folder and file creation and placement process cannot occur until after the partitioning and formatting of the storage device. The decision to implement one or more partitions per storage device is based on certain advantages and disadvantages.

Fast Facts

Creating multiple partitions on your storage device:

Improves access time for data and applications colocated on the same partition

Supports the separation of user files and operating system files

Provides dedicated operating system swap or system paging file space

Protects operating system files from the rapid growth of system data files (for example, logging and system cache) that may consume all available disk space quickly

Provides support for multibooting environments

Provides a layer of isolation to prevent or protect one partition's system resources from another partition's system resources

Allows the implementation of various filesystems and different disk geometry strategies to improve read and/or write performance

After creating a partition, a filesystem must be assigned to it via a partition editor tool or via the mkfs command. A directory structure would then need to be created for the allocation and organization of files and folders. The balancing of the size and structure of the partitions, filesystems, and directories must be addressed, with decisions based on.

■

Initial boot access: During the installation process, it is critical the system BIOS (basic input/output system) and GRUB (grand unified bootloader) functions are able to access a partition. The system BIOS will access the primary partition to execute the bootloader, GRUB, which must be able to access the /boot partition to retrieve the Linux kernel and other critical configuration files. As a result, for some installations, placing the initial boot applications and configuration files on a separate partition makes the installation process easier, especially as, during the initial boot process, the Linux kernel and initrd will have limited access to disk device drivers.

Disk space growth: The design and implementation of a Linux system require disk space growth projections. The amount of disk space needed for current and future use needs to be calculated, and the projections should include installed applications and application data and user files. If a fixed partition-based implementation is used, space limitations or quotas should be used. The introduction of logical volume management (LVM) reduces disk growth limitations by allowing data in volumes to expand across separate physical disks.

Security and permissions: Information stored on the same partition opens the door for various security risks. For example, if the partition is corrupted, all the data could be lost. In addition, directories not properly secured could give unauthorized users access to sensitive data (for example, everybody's HR records in a company). Creating separate partitions to segregate system resources from user files allows you to place more stringent access controls around system resources.

Backup/restore: Creating several partitions provides greater backup flexibility, reduces backup performance impacts, and can improve restoration times.

System repair/rescue: Creating a separate partition for critical partitions makes it easier to repair and/or rescue a corrupted partition.

Logging/monitoring: Log files must be accessed, reviewed, and in most cases saved for security purposes. The creation of a separate partition for log files will make it easy to backup, restore, and secure these.

Volatile/temporary data: Computers and associated applications are constantly creating volatile and temporary data. The Linux system automatically creates a swap partition to hold some of this data. However, there are other directories (for example, /tmp) that traditionally reside underneath the root directory. These other directories can also outgrow the disk space capacity of the partition.

System maintenance: The creation of separate partitions for system administration and maintenance purposes can also make the job easier.

The decision to create a partition or not to create a partition is difficult. Clearly, a single partition system is not a sound system design; however, creating a partition for every directory is not feasible either. Table 2.2 provides more insight into why some directories are put on separate partitions.

Table 2.2. Linux Directories and Partitions

The recommended partitioning schema is to have two primary partitions and one extended partition. The two primary partitions support the Linux root partition and the Linux swap partition. The extended partition supports the home partition.

Exam Warning

When deciding on the size of the partitions, bear in mind that the BIOS in some older computers may be able to access the first 1024 cylinders of a disk drive, approximately 528 MB.