“UbuntuHelp:ServerFaq”的版本间的差异

2008年12月16日 (二) 20:04的版本

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https://help.ubuntu.com/community/ServerFaq

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This is a FAQ document for the Ubuntu Server

This Frequently-Asked-Questions document is intended to help system administrators and users of the Ubuntu Server edition. See the section sources at the bottom of the page for more information. And please update the document if you have new information or even new questions :-)

How do I partition the, server?

Partitioning a server's disk space is more art then science. Using Logical Volume Manager (LVM) and RAID hardware or software allows greater flexibility in terms of disk layout. Partitions using LVM can be easily expanded to meet future requirements. A common partition configuration is to have /home, /opt, /usr, /var, /tmp, and /srv on separate partitions from /. Depending on the services provided by the server and where you wish to store your data will determine how much space each partition is alloted. Ubuntu complies with the Filesystem Hierarchy Standard, where you will get additional information on which is what. As an example we have a home web server that will also serve files to Windows clients using Samba. The server has one 250G hard drive and will be partitioned:

This is just an example there are many other ways that the space can be used, but however you decide to partition your drives using LVM is a good idea in case things change and a partition requires more space. See the LVM HOWTO for more details on setting up LVM. Also, Installation|LVM on RAID wiki page has some good information.

What's the difference between desktop and server?

• The first difference is in the CD contents. I hope that the desktop version doesn't need an explanation, while the "Server" CD instead of having packages like X, Gnome or KDE has that can be useful on a server: Apache2, Bind9 and so on. Using a Desktop CD with a minimal installation and installing, for example, apache2 from the network, one can obtain the exact same result that can be obtained by inserting the Server CD and installing apache2 from the cd-rom.
• The Ubuntu Server Edition installation process is slightly different then the Desktop Edition. Since by default Ubuntu Server doesn't have a GUI the process is menu driven, very similar to the Alternate CD installation process.
• Ubuntu server install by default a server optimized kernel.
• Ubuntu Desktop will receive a 3 years support, Ubuntu Server will be supported for 5 years.

What is the maintenance period of my server?

You get free security updates for at least 18 months on the desktop and server. With the Long Term Support (LTS) version you get three years support on the desktop, and five years on the server.

Can I add a "Graphic User Interface", [GUI] To a Server?

Yes you can, depending on what window manager you wish to use you can install the xserver and the window manager via apt-get. For details see the ServerGUI page.

Where can I find the Ubuntu server CD images?

• http://www.ubuntu.com/getubuntu/download to get official images
• http://cdimage.ubuntu.com/ubuntu-server/ for all builds (including unsupported ones)

Where can I get help?

For Ubuntu Server related questions, community support is available from:

• The mailing list, https://lists.ubuntu.com/mailman/listinfo/ubuntu-server
• The IRC Channel, server: irc.freenode.net - channel: #ubuntu-server
• The forum, http://ubuntuforums.org/forumdisplay.php?f=45

Commercial Support:

• Available from Canonical: http://www.canonical.com/services/support

How do I tell if my question is Ubuntu Server related?

A common pitfall is considering a problem server related because the server version, and not the desktop one, is installed. But if you have read the previous paragrahps you know that they share a lot, so where the problem belongs is not given. Here a list of things you want to take into account when deciding:

• If your problem is hardware related, is your machine a real server or a common pc acting as such?
• If it's a software problem, is it about one of the officially supported applications (see the paragraph about supported packages later on this page)?
• If it's a kernel related problem, is it about something specific to the server's one?
• As a rule of thumb any generic question like "how do I install application xyz?" does not belong to ubuntu server

Anyway do not be scared of asking, if the place is not appropriate for your question you will be simply redirected to the right one.

When will new versions of Ubuntu server be released?

Ubuntu server follows the same release plan as Ubuntu desktop: https://wiki.ubuntu.com/Releases

Are there different repositories for desktop and server?

No, there are no desktop and server-specific repositories. This means that you can install server packages on an Ubuntu Desktop installation as well as a Ubuntu Server Edition install.

How does the package system (apt) know what to install/update (server or desktop packages)?

It doesn't. The sysadmin should know what he/she is installing. While upgrading/updating packages (apt-get update && apt-get upgrade) apt will update only the packages already installed on the system. There are also some packages available to automate the process. One is apticron a cron script that will email an administrator with details about which packages are ready for updating. The unattended-upgrades package can be configured to automatically install security updates, or all updates.

Where can I find a list of packages included with Ubuntu Server?

The Ubuntu Packages Search page provides an easy way to browse and search the thousands of packages available.

What (packages/repositories) will be supported?

Not all packages in the main repository are supported:

• Dapper : there is a list of supported Dapper packages here: http://people.ubuntu.com/~cjwatson/seeds/ubuntu-server-dapper/serverThese packages are supported 5 years.
• Hardy and beyond: All packages that are part of the the seeds "server-ship" or "supported-common" are supported for five years. To check out the seed, see germinate's output at: http://people.ubuntu.com/~ubuntu-archive/germinate-output/

All other packages in main are supported 3 years, all other packages (universe, multiverse, etc) are not official supported but may be getting some support from the community or an ISV. Be aware that apt does not check if a package is supported or not, you have to do that on your own.

What happens if I install packages that are not supported? Are there security patches for five years for those packages also?

If you install packages that are not supported, you are on your own. No security update is committed to be provided for unsupported packages or bug fixes.

Is my RAID Controller supported?

If it is a SATA controller, take a look at the page http://linuxmafia.com/faq/Hardware/sata.html if it is a fakeraid they say that you are better off using Linux Software RAID.

Does the Ubuntu Server support Software RAID?

Software RAID is often a less expensive, and more flexible alternative to hardware RAID. Furthermore, there's no special hardware required for Software RAID -- just disks. The Ubuntu Server installer supports partitioning and installation onto RAID0 (striping), RAID1 (mirroring), and RAID5 (striped set with distributed parity), with a few caveats. Some considerations...

• LVM is generally preferred over RAID0 to attain the same effect (concatenating storage across multiple disks), as it allows for more flexible extendability.
• This might make sense for auxiliary storage, but you would not want to spread your root filesystem over multiple disks, as a failure of any disk would render the system unbootable.
• For full redundancy of the entire system, you can install the Ubuntu Server to a root filesystem on a RAID1 mirror.
• If you wish to install the Ubuntu Server to a root filesystem on a RAID5 set, you will need to create a separate /boot filesystems on a RAID1 mirror.

For more info about Ubuntu and RAID you can take a look to: Raid Installation/LVMOnRaid FakeRaidHowto

Is a dedicated SMP kernel available from Ubuntu Server install CD?

No, there is no dedicated SMP kernel. The kernel has been patched to support both uni-processors and smp at the same time without performance hit. The minimum requirement for the server kernel is that your architecture supports PAE (which allows addressing of more than 3G of RAM).

Which kernels versions/types are available on the Ubuntu Server CD?

The kernel on the CD will depend on which ISO you have downloaded.

• *-server-i386.iso -- contains the x86 kernel.
• *-server-amd64.iso -- contains the amd64 kernel.

There is also an option to install a virtual|kernel as part of a minimal virtual installation by pressing F4 on the first installer screen.

What's the difference between kernel linux-image-server and linux-image-generic? What architecture is linux-image-server? Which one should I use?

The linux-image-server package is a meta package that will install the latest Server kernel version, while the linux-image-generic package is a meta package for the latest Desktop kernel version. The server pages include some details on the specific kernel optimizations made for servers. linux-image-server is used for both architectures x86 and amd64. Which one you should use will depend on the type of system you have. If you have a 64 bit processor you can use the amd64 architecture, or the x86 architecture. However, if your processor is 32 bit you can only use the x86 kernel.

Are there also server images for other hardware architectures?

Currently only x86 and amd64 architectures are officially supported. Other architectures (sparc, ppc, etc...) can be found on http://cdimage.ubuntu.com/ but they are not currently officially supported.

Do I have to choose the kernel for my system on my own?

Depending on the installation method, a proper kernel is installed for your system. It is also possible to install a different kernel after installation. For example, if you have installed Ubuntu Server Edition then decide to install a wireless network card, it may be better to use the generic kernel and modules. The generic kernel can be installed from a terminal by entering: sudo apt-get install linux-generic linux-restricted-modules

What are the differences between server and virtual kernels?

The difference between the Virtual and Server kernels, is that the Virtual Kernel is intended to be utilized inside a Virtual Machine environment. The virtual kernel only includes the necessary drivers to run inside popular virtualization technologies such as KVM, Xen, and VMWare. The server kernel in contrast contains the necessary drivers to work with a wide range of hardware, and should be installed directly on host systems. Other than that all other options are identical between the server and the virtual kernel. For the difference between generic and the server kernel, see the above|question.

How do I install "tasks" after the installer has ran?

The server tasks are groups of related packages that can be installed at the same time. The tasksel package is used to accomplish this. To install a task post installation simply enter sudo tasksel inside a terminal. tasksel can also be used to install non-server related tasks, such as a desktop environment. See [1] for more details.

What virtualization technologies are supported?

Currently KVM is the supported host virtualization solution. Since Intrepid, Xen is also supported as a guest (DomU) option, but not as a Dom0. VMWare, Parallel, and other virtualization option can be supported by their respective vendors/communities. Also, Xen and VMWare have a large number of user's in the community and help with these applications can generally be found. See also:

• the server virtualization page
• the KVM page for more details on how to setup KVM

Why doesn't Ubuntu provide a root account by default

Ubuntu, as all Unix or Linux system, does have a root account, it is just that the password to log into it is not set by default. This is done on purpose as explained below. Ubuntu implements a role-based administration model with no default root access. Other Linux distributions typically provide this root access but role-based administration allows for better security, error prevention and auditing. This is particularly useful on systems where more than one user might have been given root access, as in a traditional model. Privileged user that are part of the admin group can issue commands as if they were root using the sudo command, including "sudo su" which will bring them to a root prompt. The /etc/sudoers, which should be edited with the sudo visudo command, allows to specify finer execution rights for particular users or groups. All sudo action are logged as the original user, therefore allowing to trace who has done what and when. It is also much more complicated for a remote attacker to target a brute force password attack on an account when it does not know the name the account will use by default. The root account is common to all UNIX/Linux platforms, the name you will give to you privileged account is not likely to be. See also:

• https://help.ubuntu.com/community/RootSudo
• https://help.ubuntu.com/community/Sudoers

I need a root account in case of network failure

This is likely to be a misunderstanding. What you need is a local user with rights to use the sudo command (part of the admin group). Just make sure that the admin group is also a local group.

Reversing the default (not recommended)

This default can be reversed once the user is confident that root access will be secure in their particular situation. To do so type "sudo passwd root" at any command prompt from a privileged user account. This will set the password account for root which, by default, is not set. Note that this is not recommended and we strongly advise users against doing this.

About this FAQ

Sources

• http://www.ossblog.it/post/338/interview-with-the-team-leader-of-the-ubuntu-server-project
• https://lists.ubuntu.com/mailman/listinfo/ubuntu-server
• #ubuntu-server @ freenode
• the Ubuntu Server Community

New questions

If there are some common questions that you would like to see answered here, please add them below, we'll try to provide an answer as time permits. Please understand that this is not a support place, please only add questions which you feel are common enough to be placed in this FAQ.