Home > Articles

Managing Storage in Red Hat Enterprise Linux 5

This sample chapter explains common Linux partitioning options so you can determine which is best for you. It also discusses how to use access control lists to limit access to filesystems as well as how to enforce disk usage limits known as quotas
This chapter is from the book

In This Chapter

  • Understanding Partitioning
  • Understanding LVM
  • Understanding RAID
  • Understanding Clustering and GFS
  • Using Access Control Lists
  • Using Disk Quotas

Managing storage is an important responsibility. The right solution works seamlessly with little gratitude. The wrong solution can lead to many headaches and late nights of trying to recover from failed file systems or inadequate storage allocation.

During installation, you are asked which partitioning method to use. You must choose to remove Linux partitions on selected drives and create the default layout, remove all partitions on selected drives and create the default layout, use free space on selected drives and create the default layout, or create a custom layout. If you choose to create the default layout, the Logical Volume Manager (LVM) is used to divide the hard drive, and then the necessary Linux mount points are created. Alternatively, if you choose custom layout, you can instead use software RAID or create partitions directly on the hard drives. Global File Systems (GFS) and clustering are two more storage solutions available with Red Hat Enterprise Linux.

This chapter explains these partitioning options so you can determine which is best for you and you can learn how to manage them. It also discusses how to use access control lists to limit access to filesystems as well as how to enforce disk usage limits known as quotas. Analyze how your company uses storage and decide which options are best for you.

Understanding Partitioning

LVM and RAID offer benefits such as resizing, striping, and combining multiple hard drives into logical physical devices. Sometimes it is necessary to just create partitions on the hard drives. Even when using RAID, partitions are created before the LVM or RAID layer is implemented.

To view a list of partitions on the system, use the fdisk -l command as root. As you can see from Listing 7.1, the output shows each partition along with its device name, whether it is a bootable partition, the starting cylinder, the ending cylinder, the number of blocks, the filesystem identification number used by fdisk, and the filesystem type.

Listing 7.1. Partitioning Scheme with Standard Partitions

Disk /dev/sda: 100.0 GB, 100030242816 bytes
255 heads, 63 sectors/track, 12161 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1        1147     9213246   83  Linux
/dev/sda2            1148        4334    25599577+  83  Linux
/dev/sda3            4335        4399      522112+  82  Linux swap / Solaris
/dev/sda4            4400       12161    62348265    5  Extended
/dev/sda5            4400       12161    62348233+  83  Linux

If the system uses LVM or RAID, the fdisk -l output will reflect it. For example, Listing 7.2 shows the output for a system partitioned with LVM. There are fewer partitions shown because the logical volumes are inside the logical volume group. The first partition shown is the /boot partition because it can’t be inside a logical volume group.

Listing 7.2. Partitioning Scheme with LVM

Disk /dev/sda: 300.0 GB, 300090728448 bytes
255 heads, 63 sectors/track, 36483 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1               1          13      104391   83  Linux
/dev/sda2              14       36482    292937242+   8e  Linux LVM

During installation, the hard drives can be partitioned, given a filesystem type for formatting, and assigned a mount point as described in Chapter 1, “Installing Red Hat Enterprise Linux.” If hard drives are added to the system after installation or a hard drive has to be replaced, it is important to understand how to perform these functions post-installation.

Creating Partitions

A partition can be created from free space on a hard drive. You might need to create a partition if you add a new hard drive to the system, if you left unpartitioned space on the system during installation and want to partition it, or if you are using LVM and want to create the physical volumes on a partition instead of an entire raw device.

There are two partitioning utilities in Red Hat Enterprise Linux: parted and fdisk. The parted utility is used in this chapter because it includes a resize utility and is a bit more user-friendly. For more information on fdisk, refer to the man page with the man fdisk command.

As root, issue the parted command followed by the device name such as

parted /dev/sda

You are now in an interactive parted shell, in which the commands executed manipulate the device specified. To view existing partitions from this interactive shell, type the print command at the (parted) prompt. The output should look similar to Listing 7.3. If you compare this output to the output in Listing 7.1 and Listing 7.2 from the fdisk -l command, you will see that the parted output is a little easier to read because it includes the size in user-friendly units such as megabytes and gigabytes instead of the beginning and ending cylinders from the fdisk -l output.

Listing 7.3. Partition Table from parted for Standard Partitions

Using /dev/hda
(parted) print
Disk geometry for /dev/hda: 0kB - 100GB
Disk label type: msdos
Number  Start   End     Size    Type      File system  Flags
1       32kB    9434MB  9434MB  primary   ext3         boot
2       9434MB  36GB    26GB    primary   ext3
3       36GB    36GB    535MB   primary   linux-swap
4       36GB    100GB   64GB    extended
5       36GB    100GB   64GB    logical   ext3

Once again, the output will differ depending on the partitioning scheme being used. Listing 7.4 shows output from a system using LVM and can be compared to Listing 7.2, which shows the same output from fdisk -l.

Listing 7.4. Partition Table from parted for LVM

Disk /dev/sda: 300GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start   End    Size    Type     File system  Flags
 1     32.3kB  107MB  107MB   primary  ext3
 3     107MB   300GB  299.9GB  primary               lvm

To create a partition in parted, issue the following command at the interactive parted prompt:

mkpart <part-type> <fs-type> <start> <end>

<part-type> must be one of primary, logical, or extended. <fs-type> must be one of fat16, fat32, ext2, HFS, linux-swap, NTFS, reiserfs, or ufs. The <start> and <end> values should be given in megabytes and must be given as integers.

The ext3 filesystem is the default filesystem for Red Hat Enterprise Linux. It is the ext2 filesystem plus journaling. To create an ext3 filesystem, use ext2 as the <fs-type> and then use the -j option to mke2fs to make the filesystem ext3 as described in the next section.

After creating the partition, use the print command again to verify that the partition was created. Then type quit to exit parted.

Creating a Filesystem on a Partition

Next, create a filesystem on the partition. To create an ext3 filesystem (default used during installation), as root, execute the following, where <device> is the device name for the partition such as /dev/sda1:

mke2fs -j <device>

If the partition is to be a swap partition, format it with the following command as root:

mkswap <device>

Labeling the Partition

To label the partition, execute the following as root:

e2label <device> <label>

While labeling is not required, partition labels can be useful. For example, when adding the partition to /etc/fstab, the label can be listed instead of the partition device name. This proves useful if the partition number is changed from repartitioning the drive or if the partition is moved.

If the e2label command is used with just the partition device name as an argument, the current label for the partition is displayed.

Creating a Mount Point

Now that the partition is created and has a filesystem, as root, create a directory so it can be mounted:

mkdir <dir-name>

Then, mount the new partition:

mount <device> <dir-name>

such as:

mount /dev/sda5 /tmp

Access the directory and make sure you can read and write to it.

Finally, add the partition to the /etc/fstab file so it is mounted automatically at boot time. For example:

LABEL=/tmp            /tmp               ext3    defaults        1 2

If a new swap partition is added, be sure to use swap as the filesystem type instead:

LABEL=swap2         swap                 swap    defaults        0 0

Resizing Partitions

The parted utility can also be used to resize a partition. After starting parted as root on the desired device, use the following command to resize a specific partition:

resize <minor-num> <start> <end>

To determine the <minor-num> for the partition, look at the partition table with the print command such as the output shown in Listing 7.3 and Listing 7.4. The <start> and <end> values should be the start and end points of the partition, in megabytes.

Removing Partitions

To use parted to remove a partition, start parted on the desired device as root, and issue the following command at the interactive prompt:

rm <minor-num>

The minor number for the partition is displayed when you execute the print command to list partitions. The data on the partition will no longer be accessible after the partition is removed, so be sure to back up any data you want to keep before removing the partition.

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020