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Sometimes, things go wrong, and the system you've carefully installed is no
longer bootable. Perhaps the boot loader configuration broke while trying
out a change, or perhaps a new kernel you installed won't boot, or perhaps
cosmic rays hit your disk and flipped a bit in
/sbin/init. Regardless of the cause, you'll need to
have a system to work from while you fix it, and rescue mode can be useful
for this.
To access rescue mode, type rescue at the
boot: prompt, or boot with the
rescue/enable=true boot parameter. You'll be shown
the first few screens of the installer, with a note in the corner of the
display to indicate that this is rescue mode, not a full installation. Don't
worry, your system is not about to be overwritten! Rescue mode simply takes
advantage of the hardware detection facilities available in the installer to
ensure that your disks, network devices, and so on are available to you
while repairing your system.
Instead of the partitioning tool, you should now be presented with a list of
the partitions on your system, and asked to select one of them. Normally,
you should select the partition containing the root file system that you
need to repair. You may select partitions on RAID and LVM devices as well as
those created directly on disks.
If possible, the installer will now present you with a shell prompt in the
file system you selected, which you can use to perform any necessary
repairs.
For example, if you need to reinstall the GRUB boot loader into the master
boot record of the first hard disk, you could enter the command
grub-install '(hd0)' to do so.
... Read more »
Why would someone want to compile a new kernel? It is often not
necessary since the default kernel shipped with Ubuntu handles most
configurations. Also, Ubuntu often offers several alternative kernels.
So you may want to check first if there is an alternative kernel image
package that better corresponds to your hardware. However, it can be
useful to compile a new kernel in order to:
handle special hardware needs, or hardware conflicts with the
pre-supplied kernels
use options of the kernel which are not supported in the pre-supplied
kernels (such as high memory support)
optimize the kernel by removing useless drivers to speed up boot time
create a monolithic instead of a modularized kernel
run an updated or development kernel
learn more about linux kernels
Kernel Image Management
Don't be afraid to try compiling the kernel. It's fun and profitable.
To compile a kernel the Debian/Ubuntu way, you need some packages:
fakeroot, kernel-package,
linux-source-2.6
and a few others which are probably already installed (see
/usr/share/doc/kernel-package/README.gz for the
complete list).
This method will make a .deb of your kernel source, and, if you have
non-standard modules, make a synchronized dependent .deb of those
too. It's a better way to manage kernel images;
/boot will hold the kernel, the System.map, and a
log of the active config file for the build.
Note that you don't have to compile your kernel
the "Debian/Ubuntu way”; but we find that using the packaging system
to manage your kernel is actually safer and easier. In fact, you can get
your kernel sources right from Linus instead of
linux-source-2.6,
yet still use the kernel-package compilation method.
Note that you'll find complete documentation on using
kernel-package under
/usr/share/doc/kernel-package. This section just
contains a brief tutorial.
Hereafter, we'll assume you have free rein over your machine and will
extract your kernel source to somewhere in your home directory. We'll also assume that your kernel version is
2.6.35. Make sure you are in the directory to where you want to
unpack the kernel sources, extract them using
tar xjf /usr/src/linux-source-2.6.35.tar.bz2
and change to the directory linux-source-2.6.35
that will have been created.
... Read more »
Today, email is an important part of many people's life. As there are
many options as to how to set it up, and as having it set up correctly is
important for some Ubuntu utilities, we will try to cover the basics in
this section.
There are three main functions that make up an e-mail system. First there is
the Mail User Agent (MUA) which is the program a user
actually uses to compose and read mails. Then there is the Mail
Transfer Agent (MTA) that takes care of transferring messages
from one computer to another. And last there is the Mail
Delivery Agent (MDA) that takes care of delivering incoming mail
to the user's inbox.
These three functions can be performed by separate programs, but they can
also be combined in one or two programs. It is also possible to have
different programs handle these functions for different types of mail.
On Linux and Unix systems mutt is historically a very
popular MUA. Like most traditional Linux programs it is text based. It is
often used in combination with exim or
sendmail as MTA and procmail as MDA.
With the increasing popularity of graphical desktop systems, the use of
graphical e-mail programs like GNOME's evolution,
KDE's kmail or Mozilla's thunderbird
is becoming more popular. These programs combine the function
of a MUA, MTA and MDA, but can — and often are — also be used
in combination with the traditional Linux tools.
... Read more »
If you need information about a particular program, you should first
try man program, or
info program.
There is lots of useful documentation in
/usr/share/doc as well. In particular,
/usr/share/doc/HOWTO and
/usr/share/doc/FAQ contain lots of interesting
information. To submit bugs, look at
/usr/share/doc/debian/bug*. To read about
Debian/Ubuntu-specific issues for particular programs, look at
/usr/share/doc/(package name)/README.Debian.
Ubuntu is a little different from other distributions. Even if you're
familiar with Linux in other distributions, there are things you
should know about Ubuntu to help you to keep your system in a good,
clean state. This chapter contains material to help you get oriented;
it is not intended to be a tutorial for how to use Ubuntu, but just a
very brief glimpse of the system for the very rushed.
Ubuntu Packaging System
The most important concept to grasp is the Ubuntu packaging system, which
may be familiar to those who have already used Debian GNU/Linux.
In essence, large parts of your system should be considered under the
control of the packaging system. These include:
/usr (excluding /usr/local)
/var (you could make
/var/local and be safe in there)
/bin
/sbin
/lib
For instance, if you replace /usr/bin/perl, that
will work, but then if you upgrade your perl
package, the file you put there will be replaced. Experts can get
around this by putting packages on "hold” in
aptitude.
One of the best installation methods is apt. You can use the command
line version apt-get, the full-screen text version
aptitude, or the graphical version
synaptic. Note apt will also let you merge
main, contrib, and non-free so you can have export-restricted packages
as well as standard versions.
... Read more »
If you are new to Unix, you probably should go out and buy some books
and do some reading. A lot of valuable information can also be found
in the Debian Reference.
This list of Unix FAQs contains a
number of UseNet documents which provide a nice historical reference.
Linux is an implementation of Unix. The
Linux Documentation Project (LDP)
collects a number of HOWTOs and online books
relating to Linux. Most of these documents can be installed locally;
just install the doc-linux-html package (HTML
versions) or the doc-linux-text package (ASCII
versions), then look in /usr/share/doc/HOWTO.
International versions of the LDP HOWTOs are also available as Ubuntu
packages.
To shut down a running Linux system, you must not reboot with the
reset switch on the front or back of your computer, or just turn off
the computer. Linux should be shut down in a controlled manner,
otherwise files might get lost and/or disk damage might occur. If you run a
desktop environment, there is usually an option to "log out”
available from the application menu that allows you to shutdown (or reboot)
the system.
Alternatively you can press the key combination Ctrl+Alt+Del
. A last option is to log in as root and type one of the
commands poweroff, halt or
shutdown -h now if either of the key combinations do not
work or you prefer to type commands; use reboot to reboot
the system.
Once your system boots, you'll be presented with the login
prompt. Log in using the personal login and password you
selected during the installation process. Your system is now ready for use.
If you are a new user, you may want to explore the documentation which
is already installed on your system as you start to use it. There are
currently several documentation systems, work is proceeding on
integrating the different types of documentation. Here are a few
starting points.
Documentation accompanying programs you have installed can be found in
/usr/share/doc/, under a subdirectory named after the
program (or, more precise, the Debian package that contains the program).
However, more extensive documentation is often packaged separately in
special documentation packages that are mostly not installed by default.
For example, documentation about the package management tool
apt can be found in the packages
apt-doc or apt-howto.
In addition, there are some special folders within the
/usr/share/doc/ hierarchy. Linux HOWTOs are
installed in .gz (compressed) format, in
/usr/share/doc/HOWTO/en-txt/. After installing
dhelp, you will find a browsable index of
documentation in /usr/share/doc/HTML/index.html.
... Read more »
If you created encrypted volumes during the installation and assigned
them mount points, you will be asked to enter the passphrase for each
of these volumes during the boot. The actual procedure differs
slightly between dm-crypt and loop-AES.
dm-crypt
For partitions encrypted using dm-crypt you will be shown the following
prompt during the boot:
Starting early crypto disks... part_crypt(starting)
Enter LUKS passphrase:
In the first line of the prompt, part is the
name of the underlying partition, e.g. sda2 or md0.
You are now probably wondering
for which volume you are actually entering the
passphrase. Does it relate to your /home? Or to
/var? Of course, if you have just one encrypted
volume, this is easy and you can just enter the passphrase you used
when setting up this volume. If you set up more than one encrypted
volume during the installation, the notes you wrote down as the last
step in the section called "Configuring Encrypted Volumes” come in handy. If you did not
make a note of the mapping between
part_crypt and the mount
points before, you can still find it
in /etc/crypttab
and /etc/fstab of your new system.
The prompt may look somewhat different when an encrypted root file system is
mounted. This depends on which initramfs generator was used to generate the
initrd used to boot the system. The example below is for an initrd generated
using initramfs-tools:
No characters (even asterisks) will be shown while entering the passphrase.
If you enter the wrong passphrase, you have two more tries to correct it.
After the third try the boot process will skip this volume and continue to
mount the next filesystem. Please see the section called "Troubleshooting”
for further information.
After entering all passphrases the boot should continue as usual.
... Read more »
Your system's first boot on its own power is what electrical engineers
call the "smoke test”.
If you did a default installation, the first thing you should see when you
boot the system is the menu of the grub or possibly
the lilo bootloader.
The first choices in the menu will be for your new Ubuntu system. If you
had any other operating systems on your computer (like Windows) that were
detected by the installation system, those will be listed lower down in the
menu.
If the system fails to start up correctly, don't panic. If the installation
was successful, chances are good that there is only a relatively minor
problem that is preventing the system from booting Ubuntu. In most cases
such problems can be fixed without having to repeat the installation.
One available option to fix boot problems is to use the installer's
built-in rescue mode (see the section called "Recovering a Broken System”).
If you had any other operating systems on your computer that were not detected
or not detected correctly, please file an installation report.
As described in the section called "Devices Requiring Firmware”, some devices require
firmware to be loaded. In most cases the device will not work at all
if the firmware is not available; sometimes basic functionality is not
impaired if it is missing and the firmware is only needed to enable
additional features.
If a device driver requests firmware that is not available, debian-installer will
display a dialog offering to load the missing firmware. If this option
is selected, debian-installer will scan available devices for either loose firmware
files or packages containing firmware. If found, the firmware will be
copied to the correct location (/lib/firmware) and
the driver module will be reloaded.
Which devices are scanned and which file systems are supported depends on
the architecture, the installation method and the stage of the installation.
Especially during the early stages of the installation, loading the firmware
is most likely to succeed from a FAT-formatted floppy disk or USB stick.
On i386 and amd64 firmware can also be loaded from an
MMC or SD card.
Note that it is possible to skip loading the firmware if you know the
device will also function without it, or if the device is not needed during
the installation.
Support for loading firmware is still relatively basic and is likely to
be improved in future releases of the installer. Currently debian-installer will
for example not display any warning if you choose to load missing firmware,
but the requested firmware is not found.
Please report any issues you encounter by filing an installation report
(see the section called "Submitting Installation Reports”).
Preparing a medium
Although in some cases the firmware can also be loaded from a partition on
a hard disk, the most common method to load firmware will be from some
removable medium such as a floppy disk or a USB stick.
The firmware files or packages must be placed in either the root directory
or a directory named /firmware of the file system on
the medium. The recommended file system to use is FAT as that is most
certain to be supported during the early stages of the installation.
Tarballs containing current packages for the most common firmware are
available from:
Just download the tarball for the correct release and unpack it to the file
system on the medium.
If the firmware you need is not included in the tarball, you can also
download specific firmware packages from the (non-free section of the)
archive. The following overview should list most available firmware
packages but is not guaranteed to be complete and may also contain
non-firmware packages:
It is also possible to copy individual firmware files to the medium. Loose
firmware could be obtained for example from an already installed system or
from a hardware vendor.
... Read more »
Here is a list of installer components with a brief description
of each component's purpose. Details you might need to know about
using a particular component are in the section called "Using Individual Components”.
main-menu
Shows the list of components to the user during installer operation,
and starts a component when it is selected. Main-menu's
questions are set to priority medium, so if your priority is set to
high or critical (high is the default), you will not see the menu. On
the other hand, if there is an error which requires your intervention,
the question priority may be downgraded temporarily to allow you
to resolve the problem, and in that case the menu may appear.
You can get to the main menu by selecting the Go Back button
repeatedly to back all the way out of the currently running component.
... Read more »
The Ubuntu Installer (based on the Debian Installer, and so often called
simply debian-installer) consists of a number of special-purpose
components to perform each installation task. Each component performs
its task, asking the user questions as necessary to do its job.
The questions themselves are given priorities, and the priority
of questions to be asked is set when the installer is started.
When a default installation is performed, only essential (high priority)
questions will be asked. This results in a highly automated installation
process with little user interaction. Components are automatically run
in sequence; which components are run depends mainly on the installation
method you use and on your hardware. The installer will use default values
for questions that are not asked.
If there is a problem, the user will see an error screen, and the
installer menu may be shown in order to select some alternative
action. If there are no problems, the user will never see the
installer menu, but will simply answer questions for each component
in turn. Serious error notifications are set to priority
"critical” so the user will always be notified.
Some of the defaults that the installer uses can be influenced by passing
boot arguments when debian-installer is started. If, for example, you wish to
force static network configuration (DHCP is used by default if available),
you could add the boot parameter netcfg/disable_dhcp=true.
See the section called "Ubuntu Installer Parameters” for available options.
Power users may be more comfortable with a menu-driven interface,
where each step is controlled by the user rather than the installer
performing each step automatically in sequence. To use the installer
in a manual, menu-driven way, add the boot argument
priority=medium.
If your hardware requires you to pass options to kernel modules as
they are installed, you will need to start the installer in
"expert” mode. This can be done by either using the
expert command to start the installer or by adding
the boot argument priority=low.
Expert mode gives you full control over debian-installer.
For this architecture the debian-installer supports two different user interfaces: a
character-based one and a graphical one. The character-based interface is
used by default unless you selected the "Graphical install”
option in the initial boot menu. For more information about the
graphical installer, please refer to the section called "The Graphical Installer”.
In the character-based environment the use of a mouse is not supported.
Here are the keys you can use to navigate within the
various dialogs. The Tab or right
arrow keys move "forward”, and the Shift+Tab or left arrow keys
move "backward” between displayed buttons and selections.
The up and down arrow select
different items within a scrollable list, and also scroll the list
itself. In addition, in long lists, you can type a letter to cause the
list to scroll directly to the section with items starting with the
letter you typed and use Pg-Up and
Pg-Down to scroll the list in sections. The
space bar selects an item such as a checkbox. Use
Enter to activate choices.
... Read more »
Sometimes, especially with older CD-ROM drives, the installer may fail
to boot from a CD-ROM. The installer may also — even after booting
successfully from CD-ROM — fail to recognize the CD-ROM or return
errors while reading from it during the installation.
There are many different possible causes for these problems. We can
only list some common issues and provide general suggestions on how to
deal with them. The rest is up to you.
There are two very simple things that you should try first.
If the CD-ROM does not boot, check that it was inserted correctly and that
it is not dirty.
If the installer fails to recognize a CD-ROM, try just running the option
Detect and mount CD-ROM
a second time. Some DMA related issues with older CD-ROM drives are known to
be resolved in this way.
If this does not work, then try the suggestions in the subsections below.
Most, but not all, suggestions discussed there are valid for both CD-ROM and
DVD, but we'll use the term CD-ROM for simplicity.
If you cannot get the installation working from CD-ROM, try one of the
other installation methods that are available.
Common issues
Some older CD-ROM drives do not support reading from discs that were burned
at high speeds using a modern CD writer.
If your system boots correctly from the CD-ROM, it does not necessarily
mean that Linux also supports the CD-ROM (or, more correctly, the controller
that your CD-ROM drive is connected to).
Some older CD-ROM drives do not work correctly if "direct memory
access” (DMA) is enabled.
Boot parameters are Linux kernel parameters which are generally used
to make sure that peripherals are dealt with properly. For the most
part, the kernel can auto-detect information about your peripherals.
However, in some cases you'll have to help the kernel a bit.
If this is the first time you're booting the system, try the default
boot parameters (i.e., don't try setting parameters) and see if it works
correctly. It probably will. If not, you can reboot later and look for
any special parameters that inform the system about your hardware.
should be emitted early in the process.
total should match the total amount of RAM,
in kilobytes. If this doesn't match the actual amount of RAM you have
installed, you need to use the
mem=ram parameter,
where ram is set to the amount of memory,
suffixed with "k” for kilobytes, or "m” for
megabytes. For example, both mem=65536k and
mem=64m mean 64MB of RAM.
If you are booting with a serial console, generally the kernel will
autodetect this.
If you have a videocard (framebuffer) and a keyboard also attached to
the computer which you wish to boot via serial console, you may have
to pass the
console=device
argument to the kernel, where device is
your serial device, which is usually something like
ttyS0.
Ubuntu Installer Parameters
The installation system recognizes a few additional boot parameters which may be useful.
A number of parameters have a "short form” that helps avoid
the limitations of the kernel command line options and makes entering the
parameters easier. If a parameter has a short form, it will be listed in
brackets behind the (normal) long form. Examples in this manual will
normally use the short form too.
debconf/priority (priority)
This parameter sets the lowest priority of messages to be displayed.
The default installation uses priority=high.
This means that both high and critical priority messages are shown, but medium
and low priority messages are skipped.
If problems are encountered, the installer adjusts the priority as needed.
If you add priority=medium as boot parameter, you
will be shown the installation menu and gain more control over the installation.
When priority=low is used, all messages are shown
(this is equivalent to the expert boot method).
With priority=critical, the installation system
will display only critical messages and try to do the right thing without fuss.
... Read more »
Some users may need specific support because of e.g. some visual
impairment.
USB braille displays are detected
automatically, but most other
accessibility features have to be enabled manually.
On machines that support it, the boot menu emits a beep
when it is ready to receive keystrokes.
Some boot parameters can then be appended to
enable accessibility features. Note that on most architectures the boot
loader interprets your keyboard as a QWERTY keyboard.
USB Braille Displays
USB braille displays should be automatically detected. A textual version
of the installer will then be automatically selected, and support for the
braille display will be automatically installed on the target system.
You can thus just press Enter at the boot menu.
Once brltty is started, you can choose a braille
table by entering the preference menu. Documentation on key
bindings for braille devices is available on the brltty website.
Serial Braille Displays
Serial braille displays cannot safely be automatically detected
(since that may damage some of them). You thus need to append the
brltty=driver,port,table
boot parameter to tell brltty which driver it
should use. driver should be replaced by the
two-letter driver code for your terminal (see the
driver code list).
port should be replaced by the name of the
serial port the display is connected to, ttyS0 is
the default. table is the name of the braille
table to be used (see the table code
list); the English table is the default. Note that the table can
be changed later by entering the preference menu. Documentation on key
bindings for braille devices is available on the brltty website.
Hardware Speech Synthesis
Support for hardware speech synthesis devices is available only alongside
support for graphical installer. You thus need to select the
"Graphical install” entry in the boot menu.
Hardware speech synthesis devices cannot be automatically detected. You
thus need to append the
speakup.synth=driver
boot parameter to tell speakup which driver it should
use. driver should be replaced by the driver code
for your device (see driver code
list). The textual version of the installer will then be
automatically selected, and support for the speech synthesis device will be
automatically installed on the target system.
Board Devices
Some accessibility devices are actual boards that are plugged inside the
machine and that read text directly from the video memory. To get them
to work framebuffer support must be disabled by using the
vga=normalfb=false
boot parameter. This will however reduce the number of available languages.
If desired a textual version of the bootloader can be activated before adding
the boot parameter by typing hEnter.
If you have any other operating systems on your system that you wish to
keep (dual boot setup), you should make sure that they have been properly
shut down before you boot the installer.
Installing an operating system while another operating system is in
hibernation (has been suspended to disk) could result in loss of, or damage
to the state of the suspended operating system which could cause problems
when it is rebooted.
The easiest route for most people will be to use an Ubuntu CD.
If you have a CD, and if your machine supports booting directly off
the CD, great! Simply
configure your system for booting off a CD as described in
the section called "Boot Device Selection”,
insert your CD, reboot, and proceed to the next chapter.
Note that certain CD drives may require special drivers, and thus be
inaccessible in the early installation stages. If it turns out the
standard way of booting off a CD doesn't work for your hardware,
revisit this chapter and read about alternate kernels and installation
methods which may work for you.
If you intend to use the hard drive only for booting and then
download everything over the network, you should download the
netboot/ubuntu-installer/i386/initrd.gz file and its
corresponding kernel
netboot/ubuntu-installer/i386/linux. This will allow you
to repartition the hard disk from which you boot the installer, although you
should do so with care.
For LILO, you will need to configure two
essential things in /etc/lilo.conf:
to load the initrd.gz installer at boot time;
have the vmlinuz kernel use a RAM disk as
its root partition.
For more details, refer to the
initrd(4) and
lilo.conf(5) man pages. Now run
lilo and reboot.
The procedure for GRUB is quite similar. Locate your
menu.lst in the /boot/grub/
directory (or sometimes /boot/boot/grub/) and add an
entry for the installer, for example (assuming /boot
is on the first partition of the first disk in the system):
title New Install
root (hd0,0)
kernel /boot/newinstall/vmlinuz
initrd /boot/newinstall/initrd.gz
From here on, there should be no difference between GRUB
or LILO.
![[Note]](https://help.ubuntu.com/10.10/libs/admon/note.png)
![[Warning]](https://help.ubuntu.com/10.10/libs/admon/warning.png)