Home > Articles > Operating Systems, Server > Linux/UNIX/Open Source

  • Print
  • + Share This
Like this article? We recommend

Kernel

This section describes the kernel and includes reference tables for kernel-related parallels between Linux and Solaris and file system types. This section contains the following topics:

  • "Versions"

  • "Configuring and Compiling"

  • "Modules and Drivers"

  • "File Systems"

  • "Swap"

Versions

Kernel versions in Linux follow a scheme of x.y.z, where x is the major release number, y is the minor release number, and z is the feature or bug fix release level. The major release level is currently 2. An even number for y represents stable kernel releases where only bug fixes are applied as updates. An odd number for y represents a development release, where new features can be added as updates. For example 2.0, 2.2, and 2.4 are stable production kernels, whereas 2.1, 2.3, and 2.5 are development kernels. When a development kernel reaches a critical mass in new features, a new production version is released.

The z number is analogous to a Solaris kernel update patch (KUP) revision number. It represents the feature release level for development kernels, and the bug fix level for stable kernels.

The standard way to update your kernel in Redhat Linux is to use rpm(8) to install a new binary release of it. If you have a custom kernel, you can update it by applying a source-code patch, in which case you need to recompile the kernel.

The kernel source and patches are available from http://www.kernel.org.

Configuring and Compiling

With Solaris 9 OE, just plugging in a new hardware component may be all that is required to install it. More commonly, a pkgadd and reboot is done. It all depends on whether the driver is native in Solaris, and whether the hardware can be physically installed without bringing the system down.

The stock kernel installed by default in Redhat Linux can recognize and load drivers for a wide array of hardware, so it may be sufficient for most purposes. If either your hardware requirements go beyond what is in the stock kernel, or you want to remove unneeded drivers built in to the kernel, a kernel rebuild is required. The details of the process are beyond the scope of this article, but the general steps are as follows:

  1. Install the kernel source tree in /usr/src.

  2. Build the configuration in /usr/src/linux via make config, make menuconfig, or make xconfig.

  3. Build the kernel dependencies via make dep.

  4. Build the kernel itself via make.

  5. Build all components you designated to run as modules in step 2 via make modules.

  6. Make a backup copy of your current kernel, and put a corresponding entry for it in /etc/lilo.conf or /boot/grub/grub.conf.

  7. Install the kernel via make install (installs the kernel into /boot and runs LILO).

  8. Install your modules via make install_modules (installs modules into /lib/modules/'uname -r').

  9. Reboot using the new kernel.

The configuration phase of building a new kernel (step 2 in the previous list) creates a file called .config in the main kernel source directory. It's a good practice to save a copy of this file elsewhere after you get a good working configuration. If you find yourself upgrading to a new kernel with a new source tree, you can usually just copy this file into the new kernel directory.

More information on building custom kernels is on the Web at: http://www.ibiblio.org/pub/Linux/docs/HOWTO/other-formats/html_single/Kernel-HOWTO.html.

Modules and Drivers

The Solaris kernel is entirely modular. The kernel itself performs a core functionality with anything beyond that requiring it to dynamically load a chunk of code to perform the task. These chunks of code are in the form of dynamically linked loadable modules. The Linux kernel can be modular in this fashion, if it is built that way from source. Most drivers have the option of being modules, or being compiled into the kernel itself. However, if a driver is needed as a component required to access the root file system, then compiling it as a module requires you to use an initial RAM disk (initrd) as part of the boot process. The initrd allows you to have a root file system accessible, complete with /lib/modules directory, before the real root file system is mounted. Solaris avoids this situation by using a file-system-aware boot loader (ufsboot) that is capable of finding the required modules within a UNIX file system (UFS) before the root file system is actually mounted.

By default, the Solaris kernel searches for modules from the following four directories in this order:

  • /platform/'uname -i'/kernel

  • /platform/'uname -m'/kernel

  • /kernel

  • /usr/kernel

If you add a new module, you can load it into the kernel immediately by installing it into one of these directories, running add_drv to assign it a major number, and running devfsadm to create the device nodes needed to access the new hardware or protocol.

Linux modules are located in /lib/modules/'uname -r'. To add a module dynamically into a running kernel, compile it and install it into /lib/modules/'uname -r'. Then use the depmod -a command to map out any dependencies for the module. If depmod comes up with unresolved dependencies, it's possible that you need to recompile the kernel to resolve the dependencies.

After running depmod successfully, use modprobe or insmod to load the module. The modprobe command checks the dependencies mapped out by depmod and automatically loads any modules deemed as dependencies. For example, if you have sunrpc and nfsd compiled as kernel modules and modprobe loads the nfsd module, the sunrpc module is automatically loaded first, because the networked file system (NFS) needs remote procedure call (RPC) to operate. The insmod command is the same as modprobe, except that it does not check for dependencies. If there is a dependency that is not satisfied, insmod fails and displays an error message about unresolved dependencies.

The module interface in Linux has a configuration file called /etc/modules.conf. In this file, you can create module aliases, set driver options, and execute commands to run before or after a module is loaded.

Both the modprobe and depmod commands reference this file. Driver parameters are set via an options statement for the module in the /etc/modules.conf file, similar to the way you set them in /etc/system or kernel/drv/<module>.conf in Solaris. Possible driver parameters for a module can be listed via modinfo -p <modulename>. If the module supports it, you can also set parameters via the proc file system interface, or the sysctl command, which uses the proc file system interface. Retrieving and setting module parameters using the proc interface is generally accomplished by manipulating the contents of files located in the /proc directory. TABLE 3 shows the module-related parallels between Solaris and Linux.

TABLE 3 Module-Related Parallels Between Solaris and Linux

Solaris

Linux

Purpose

modinfo

lsmod

List loaded modules

modload

modprobe/insmod

Load a module

modunload

rmmod

Unload a module

add_drv

depmod*

Install a new module

ndd -get

modinfo -p

or

/proc file system interface

Get module parameters

/etc/system

or

kernel/drv/<module>.conf

options line for module in /etc/modules.conf

or

modprobe <module> symbol=value

or

insmod <module> symbol=value

Set module parameters at module load time

ndd -set

sysctl / proc file system interface

Set module parameters on the fly

/etc/driver_aliases

alias option in /etc/modules.conf

Module aliases

/etc/name_to_major

Fixed list if not using devfs. See "Device Nodes" on page 8.

Module major numbers


*Not an exact comparison. Because major and minor numbers are predefined in Linux, the functionality that Solaris gets from add_drv is not needed in Linux. Running depmod is just the final step in adding a module to a system.

A STREAMS driver implementation called LiS is available in Linux. The implementation is built outside of the kernel source tree and runs as a loadable module. You can download LiS from http://www.gcom.com/.

File Systems

One of the advantages to an open-source operating environment like Linux is that when you want to get something to work, somebody has probably already written a driver for it. This includes file system drivers. For example, in Redhat 8.0, there are no less than 31 file system types supported. However, some of these file system types were ported for read-only access, with an experimental interface for write support. TABLE 4 lists some file system types available in Solaris and their counterparts in Linux.

TABLE 4 File System Types in Solaris and Linux

Solaris

Linux

autofs

autofs

nfs

nfs

udfs

udfs

hsfs

iso9660

procfs

proc

tmpfs

tmpfs

ufs

ufs

pcfs

msdos/vfat

ext2fs*

ext2


* A driver has been written at Sun, but is unsupported.

An installation of Linux initially boots to an environment that has different file system types mounted. TABLE 5 is a list of file systems you might find after installing.

TABLE 5 Linux File System Types

Mounted On

File System Type

Purpose

/

ext2/ext3

Standard Linux file system.

/boot

ext2/ext3

Standard Linux file system.

/proc

proc

Contains process information mapped out so that it can be accessed within a virtual file system framework. In Linux, /proc also provides an access mechanism to data contained within the kernel and kernel modules. This access mechanism is analogous to the ndd command in Solaris.

/dev/pts

devpts

Interface used to allocate pseudo tty devices.

/dev/shm

tmpfs

tmpfs interface for shared memory. A tmpfs in Linux works the same as it does in Solaris. The difference here is that the tmpfs is mounted on /dev/shm. This requirement is for glibc 2.2 and newer.


The complete list of Linux file system support taken from the mount(8) manual page is as follows: adfs, affs, autofs, coda, coherent, cramfs, devpts, efs, ext, ext2, ext3, hfs, hpfs, iso9660, jfs, minix, msdos, ncpfs, nfs, ntfs, proc, qnx4, reiserfs, romfs, smbfs, sysv, tmpfs, udf, ufs, umsdos, vfat, xenix, xfs, xiafs.

Swap

Swap space can be allocated as a file or a partition in Linux. Before swap space is used, it must be formatted via mkswap.

CAUTION

Be aware that Solaris x86 and Linux swap have the same partition types, and running mkswap on a Solaris x86 partition destroys it. See "Partition Tables" on page 18.

As in Solaris, any swap partitions defined in the file system table (/etc/fstab in Linux) are activated at boot time. In Linux, /sbin/swapon -a is the mechanism for doing this. You can remove a swap file or partition from use by the kernel with swapoff. Like Solaris, Linux users have all kinds of theories as to what size swap should be for a system, and this subject is not within the scope of this article. Like Solaris, Linux does not require the use of swap.

  • + Share This
  • 🔖 Save To Your Account

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