Frequently Asked Questions about the Ubuntu Server Edition

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 Smile :-)

Contents

  1. Frequently Asked Questions about the Ubuntu Server Edition
    1. Business Questions
      1. What's the difference between desktop and server?
      2. Can I add a "graphical user interface" (GUI) to a server?
      3. Where can I find the Ubuntu Server Edition CD images?
      4. When will new versions of Ubuntu Server be released?
    2. Maintenance and Support Questions
      1. Where can I get help?
      2. How do I tell if my question is Ubuntu Server related?
      3. What is the maintenance period of my server?
      4. Where can I find a list of packages included with Ubuntu Server?
      5. What packages and repositories are maintained (supported)?
      6. What happens if I install packages that are not supported? Are there security patches for five years for those packages also?
      7. Is my RAID controller supported?
      8. Does the Ubuntu Server support software RAID?
      9. What virtualization technologies are supported?
    3. Technical Questions
      1. How should I partition the server?
      2. Are there different repositories for desktop and server?
      3. How does the package system (apt) know what to install or update (server or desktop packages)?
      4. Is a dedicated SMP kernel available from the Ubuntu Server installation CD?
      5. Which kernel versions or types are available on the Ubuntu Server CD?
      6. What's the difference between the kernels linux-image-server and linux-image-generic? What architecture is linux-image-server? Which one should I use?
      7. Are there also server images for other hardware architectures?
      8. Do I have to choose the kernel for my system on my own?
      9. What are the differences between the server and virtual kernels?
      10. How do I install "tasks" after the installer has run?
      11. Why doesn't Ubuntu provide a root account by default?
        1. I need a root account in case of a network failure.
        2. But I *really* need to enable the root account! How do I?
  2. About This FAQ
    1. Sources
    2. New Questions

Business Questions

What's the difference between desktop and server?

  • The first difference is in the CD contents. The "Server" CD avoids including what Ubuntu considers desktop packages (packages like X, Gnome or KDE), but does include server related packages (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 from 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.
  • Before 12.04, Ubuntu server installs a server-optimized kernel by default. Since 12.04, there is no difference in kernel between Ubuntu Desktop and Ubuntu Server since linux-image-server is merged into linux-image-generic.

  • For Ubuntu LTS releases before 12.04, the Ubuntu Desktop Edition only receives 3 years of support. This was increased to 5 years in Ubuntu LTS 12.04 In contrast, all Ubuntu LTS Server Edition releases are supported for 5 years.

Can I add a "graphical user interface" (GUI) to a server?

Whilst we don't recommend running a GUI on a server for security and performance reasons, yes you can. Depending on what window manager you wish to use you can install the X Server and the window manager via apt-get. For details see the ServerGUI page.

Where can I find the Ubuntu Server Edition CD images?

When will new versions of Ubuntu Server be released?

Ubuntu Server follows the same release plan as Ubuntu Desktop: https://wiki.ubuntu.com/Releases

Maintenance and Support Questions

Where can I get help?

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

Commercial 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 paragraphs 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.

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.

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 and repositories are maintained (supported)?

Not all packages in the main repository are maintained (supported) equally in an LTS release: Server packages are maintained for 5 years, and all packages that are part of the the seeds "server-ship" or "supported-common" are supported for five years.

For regular releases, all the packages in main are maintained for 18 months.

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

For more info:

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 guaranteed 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 filesystem on a RAID1 mirror.

For more info about Ubuntu and RAID you can take a look at Raid,Installation/LVMOnRaid, and FakeRaidHowto.

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, Parallels, and other virtualization options are supported by their respective vendors and communities. Also, Xen and VMWare have a large number of users in the community and help with these applications can generally be found.

See also:

Technical Questions

How should I partition the server?

Partitioning a server's disk space is more of an art than a 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 /. The services provided by the server and where you wish to store your data will determine how much space each partition is allotted. 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:

  • mount point

    Size

    Comment

    /

    5G

    /home

    20G

    /opt

    5G

    /usr

    30G

    /tmp

    2G

    /var

    50G

    contains /var/www which will be served by Apache.

    /srv

    50G

    contains /srv/samba which will be served by Samba.

    93G

    Unpartitioned space which can be allocated as necessary using LVM.

This is just an example. There are many other ways that the space can be used, but regardless of how 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, the Installation of LVM on RAID wiki page has some good information.

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 on an Ubuntu Server installation.

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

It doesn't. The sysadmin should know what he/she is installing. When 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.

Is a dedicated SMP kernel available from the Ubuntu Server installation 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 a 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 kernel versions or 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 the kernels linux-image-server and linux-image-generic? What architecture is linux-image-server? Which one should I use?

Note: Since 12.04, there is no difference in kernel between Ubuntu Desktop and Ubuntu Server since linux-image-server is merged into linux-image-generic. If you are using an older version of Ubuntu Server, see explanation below:

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 guide includes some details on the changes made in the Server kernel.

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 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 the 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. 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 the generic and server kernels, see the above question about it.

Note: Since 12.04, there is no difference in kernel between Ubuntu Desktop and Ubuntu Server since linux-image-server is merged into linux-image-generic.

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

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 the server guide for more details.

Why doesn't Ubuntu provide a root account by default?

Ubuntu, as do all UNIX or Linux systems, 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 users that are part of the admin group can issue commands as if they were root using the sudo command, including "sudo -i" which will bring them to a root prompt. The /etc/sudoers file, which should be edited with the sudo visudo command, allows one to specify finer execution rights for particular users or groups. All sudo actions are logged as the original user, therefore allowing one to trace who has done what and when.

It is also much more complicated for a remote attacker to do 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:

I need a root account in case of a network failure.

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

But I *really* need to enable the root account! How do I?

The root account can be enabled once you are confident that root access will be secure in your particular situation. To enable it, 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

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.


ServerFaq (last edited 2012-09-09 17:09:30 by mikedep333)