[d-i-manual] 邀请：翻译新的一章 preseed
Hi,
``Debian 安装手册'' 新增加了一章 ``Appendix B. Automating the
installation using preseeding''，见附件。
由于内容比较多，为了尽快完成中文翻译，希望有兴趣的朋友一起来参与。
翻译方式：
按小节进行翻译，如 B.1.1，完成后将中文译文发送到本邮件列表的此线索内。
注意事项:
1. 脚本及其注释保持英文。
2. 常见计算机术语和 Debian 专有名词与 ``Debian 安装手册'' 其它章节保
持一致。
參考链接:
1. http://d-i.alioth.debian.org/manual/
2. http://d-i.alioth.debian.org/manual/zh_CN.i386/index.html
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Appendix B. Automating the installation using preseeding
Table of Contents
B.1. Introduction
B.1.1. Preseeding methods
B.1.2. Limitations
B.1.3. Running custom commands during the installation
B.1.4. Using preseeding to change default values
B.2. Using preseeding
B.2.1. Loading the preseed file
B.2.2. Using boot parameters to supplement preseeding
B.3. Creating a preseed file
B.4. Preseeding the first stage of the installation
B.4.1. Localization
B.4.2. Network configuration
B.4.3. Mirror settings
B.4.4. Partitioning
B.4.5. Clock and time zone setup
B.4.6. Apt setup
B.4.7. Account setup
B.4.8. Boot loader installation
B.4.9. Finishing up the first stage install
B.5. Preseeding the second stage of the installation
B.5.1. Base config
B.5.2. Package selection
B.5.3. Mailer configuration
B.5.4. X configuration
B.5.5. Preseeding other packages
B.6. Advanced options
B.6.1. Shell commands
B.6.2. Chainloading preseed files
This appendix explains the intricacies of preseeding answers to questions in
debian-installer to automate your installation.
The configuration fragments used in this appendix are also available as an
example preseed file from http://d-i.alioth.debian.org/manual/
example-preseed.txt.
B.1. Introduction
Preseeding provides a way to set answers to questions without having to
manually enter the answers while the installation is running. This makes it
possible to fully automate most types of installation and even offers some
features not available during normal installations.
Using preseeding it is possible to fill in answers to questions asked during
both the first stage of the installation (before the reboot into the new
system) and the second stage.
B.1.1. Preseeding methods
There are three methods that can be used for preseeding: initrd, file and
network. Initrd preseeding will work with any installation method and supports
preseeding of more things, but it requires the most preparation. File and
network preseeding each can be used with different installation methods. With
file and network preseeding the first few installer questions cannot be
preseeded because the preseed configuration file is only loaded after they have
been asked.
The following table shows which preseeding methods can be used with which
installation methods.
+--------------------------------------------------+
| Installation method |initrd|file|network|
|------------------------------+------+----+-------|
|CD/DVD |yes |yes |no |
|------------------------------+------+----+-------|
|netboot |yes |no |yes |
|------------------------------+------+----+-------|
|hd-media (including usb-stick)|yes |yes |no |
|------------------------------+------+----+-------|
|floppy based (cd-drivers) |yes |yes |no |
|------------------------------+------+----+-------|
|floppy based (net-drivers) |yes |no |yes |
+--------------------------------------------------+
An important difference between the preseeding methods is the point at which
the preseed configuration file is loaded and processed. For initrd preseeding
this is right at the start of the installation, before the first question is
even asked. For file preseeding this is after the CD or CD image has been
loaded. For network preseeding it is only after the network has been
configured.
In practical terms this means for file and network preseeding that the
questions about language, country and keyboard selection will already have been
asked. For network preseeding add to that any questions related to network
configuration. Some other questions that are only displayed at medium or low
priority (like the first hardware detection run) will also already have been
processed.
Obviously, any questions that have been processed before the preseeding
configuration file is loaded, cannot be preseeded. Section B.2.2, "Using boot
parameters to supplement preseeding" offers a way to avoid these questions
being asked.
B.1.2. Limitations
Although most questions used by debian-installer can be preseeded using this
method, there are some notable exceptions. You must (re)partition an entire
disk or use available free space on a disk; it is not possible to use existing
partitions. You currently cannot use preseeding to set up RAID and LVM.
B.1.3. Running custom commands during the installation
A very powerfull and flexible option offered by the preseeding tools is the
ability to run commands or scripts at certain points in the installation. See
Section B.6.1, "Shell commands" for details.
* preseed/early_command: is run as soon as the the preseeding configuration
file has been loaded
* preseed/late_command: is run just before the reboot at the end of the first
stage of the installation, but before the /target filesystem has been
unmounted
* base-config/early_command: is run early in the second stage of the
installation when base-config is starting up
* base-config/late_command: is run at the end of base-config, just before the
login prompt
B.1.4. Using preseeding to change default values
It is possible to use preseeding to change the default answer for a question,
but still have the question asked. To do this the seen flag must be reset to
"false" after setting the value for a template.
d-i foo/bar string value
d-i foo/bar seen false
B.2. Using preseeding
Of course you will first need to create a preseed file and place it in the
location from where you want to use it. Creating the preseed file is covered
later in this appendix. Putting it in the correct location is fairly
straightforward for network preseeding or if you want to read the file off a
floppy or usb-stick. If you want to include the file on a CD or DVD, you will
have to remaster the ISO image. How to get the preseed file included in the
initrd is outside the scope of this document; please consult the developers
documentation for debian-installer.
An example preseed file that you can use as basis for your preseed file is
available from http://d-i.alioth.debian.org/manual/example-preseed.txt. This
file is based on the configuration fragments included in this appendix.
B.2.1. Loading the preseed file
If you are using initrd preseeding, you only have to make sure a file named
preseed.cfg is included in the root directory of the initrd. The installer will
automatically check if this file is present and load it.
For the other preseeding methods you need to tell the installer what file to
use when you boot it. This is done by passing the kernel a boot parameter,
either manually at boot time or by editing the bootloader configuration file
(e.g. syslinux.cfg) and adding the parameter to the end of the append line(s)
for the kernel.
If you do specify the preseed file in the bootloader configuration, you might
change the configuration so you don't need to hit enter to boot the installer.
For syslinux this means setting the timeout to 1 in syslinux.cfg.
To make sure the installer gets the right preseed file, you can optionally
specify a checksum for the file. Currently this needs to be a md5sum, and if
specified it must match the preseed file or the installer will refuse to use
it.
Boot parameters to specify:
- if you're netbooting:
preseed/url=http://host/path/to/preseed.cfg
preseed/url/checksum=5da499872becccfeda2c4872f9171c3d
- if you're booting a remastered CD:
preseed/file=/cdrom/preseed.cfg
preseed/file/checksum=5da499872becccfeda2c4872f9171c3d
- if you're installing from USB media (put the preseed file in the
toplevel directory of the USB stick):
preseed/file=/hd-media/preseed.cfg
preseed/file/checksum=5da499872becccfeda2c4872f9171c3d
While you're at it, you may want to add a boot parameter debconf/priority=
critical. This will avoid most questions even if the preseeding below misses
some.
B.2.2. Using boot parameters to supplement preseeding
Some parts of the installation process cannot be automated using some forms of
preseeding because the questions are asked before the preseed file is loaded.
For example, if the preseed file is downloaded over the network, the network
setup must be done first. One reason to use initrd preseeding is that it allows
preseeding of even these early steps of the installation process.
If a preseed file cannot be used to preseed some steps, the install can still
be fully automated, since you can pass preseed values to the kernel on the
command line. Just pass path/to/var=value for any of the preseed variables
listed in the examples.
Note
The 2.4 kernel accepts a maximum of 8 command line options and 8 environment
options (including any options added by default for the installer). If these
numbers are exceeded, 2.4 kernels will drop any excess options and 2.6 kernels
will panic. For kernel 2.6.9 and later, you can use 32 command line options and
32 environment options.
For most installations some of the default options in your bootloader
configuration file, like 'vga=normal', may be safely removed which may allow
you to add more options for preseeding.
Note
It may not always be possible to specify values with spaces for boot
parameters, even if you delimit them with quotes.
B.3. Creating a preseed file
The preconfiguration file is in the format used by the debconf-set-selections
command.
* File format
* Only single space allowed between template type and value
* Relation with /var/lib/(c)debconf/templates
* Types of templates and how to provide values for them
* Most values need to be in English or codes
* Using a manual installation as base
* Finding other possible values
To check if the format of your preseed file is valid before performing an
install, you can use the command debconf-set-selections -c preseed.cfg.
B.4. Preseeding the first stage of the installation
The configuration fragments used in this appendix are also available as an
example preseed file from http://d-i.alioth.debian.org/manual/
example-preseed.txt.
Note that this example is based on an installation for the Intel x86
architecture. If you are installing a different architecture, some of the
examples (like keyboard selection and bootloader installation) may not be
relevant and will need to be replaced by debconf settings appropriate for your
architecture.
B.4.1. Localization
Setting localization values will only work if you are using initrd preseeding.
With all other methods the preseed file will only be loaded after these
questions have been asked.
The locale can be used to specify both language and country. To specify the
locale as a boot parameter, use debian-installer/locale=en_US.
# Locale sets language and country.
d-i debian-installer/locale string en_US
Keyboard configuration consists of selecting a keyboard architecture and a
keymap. In most cases the correct keyboard architecture is selected by default,
so there's normally no need to preseed it. The keymap must be valid for the
selected keyboard architecture.
# Keyboard selection.
#d-i console-tools/archs select at
d-i console-keymaps-at/keymap select us
# Example for a different keyboard architecture
#d-i console-keymaps-usb/keymap select mac-usb-us
To skip keyboard configuration preseed console-tools/archs with skip-config.
This will result in the kernel keymap remaining active.
Note
The changes in the input layer for 2.6 kernels have made the keyboard
architecture virtually obsolete. For 2.6 kernels normally a "PC" (at) keymap
should be selected.
B.4.2. Network configuration
Of course, preseeding the network configuration won't work if you're loading
your preseed file from the network. But it's great when you're booting from CD
or USB stick. If you are loading preseed files from the network, you can pass
network config parameters in using kernel boot parameters.
# netcfg will choose an interface that has link if possible. This makes it
# skip displaying a list if there is more than one interface.
d-i netcfg/choose_interface select auto
# If you have a slow dhcp server and the installer times out waiting for
# it, this might be useful.
#d-i netcfg/dhcp_timeout string 60
# If you prefer to configure the network manually, here's how:
#d-i netcfg/disable_dhcp boolean true
#d-i netcfg/get_nameservers string 192.168.1.1
#d-i netcfg/get_ipaddress string 192.168.1.42
#d-i netcfg/get_netmask string 255.255.255.0
#d-i netcfg/get_gateway string 192.168.1.1
#d-i netcfg/confirm_static boolean true
# Any hostname and domain names assigned from dhcp take precedence over
# values set here. However, setting the values still prevents the questions
# from being shown, even if values come from dhcp.
d-i netcfg/get_hostname string unassigned-hostname
d-i netcfg/get_domain string unassigned-domain
# Disable that annoying WEP key dialog.
d-i netcfg/wireless_wep string
# The wacky dhcp hostname that some ISPs use as a password of sorts.
#d-i netcfg/dhcp_hostname string radish
B.4.3. Mirror settings
Depending on the installation method you use, a mirror may used both to
download additional components of the installer, the base system and to set up
the /etc/apt/sources.list for the installed system.
The parameter mirror/suite determines the suite for the installed system.
The parameter mirror/udeb/suite determines the suite for additional components
for the installer. It is only useful to set this if components are actually
downloaded over the network and should match the suite that was used to build
the initrd for the installation method used for the installation. By default
the value for mirror/udeb/suite is the same as mirror/suite.
d-i mirror/country string enter information manually
d-i mirror/http/hostname string http.us.debian.org
d-i mirror/http/directory string /debian
d-i mirror/http/proxy string
# Suite to install.
#d-i mirror/suite string testing
# Suite to use for loading installer components (optional).
#d-i mirror/udeb/suite string testing
B.4.4. Partitioning
Using preseeding to partition the harddisk is very much limited to what is
supported by partman-auto. You can choose to either partition existing free
space on a disk or a whole disk. The layout of the disk can be determined by
using a predefined recipe, a custom recipe from a recipe file or a recipe
included in the preseed file. It is currently not possible to partition
multiple disks using preseeding nor to set up RAID or LVM.
Warning
The identification of disks is dependent on the order in which their drivers
are loaded. If there are multiple disks in the system, make very sure the
correct one will be selected before using preseeding.
# If the system has free space you can choose to only partition that space.
#d-i partman-auto/init_automatically_partition \
# select Use the largest continuous free space
# Alternatively, you can specify a disk to partition. The device name can
# be given in either devfs or traditional non-devfs format.
# For example, to use the first disk devfs knows of:
d-i partman-auto/disk string /dev/discs/disc0/disc
# You can choose from any of the predefined partitioning recipes:
d-i partman-auto/choose_recipe \
select All files in one partition (recommended for new users)
#d-i partman-auto/choose_recipe \
# select Separate /home partition
#d-i partman-auto/choose_recipe \
# select Separate /home, /usr, /var, and /tmp partitions
# Or provide a recipe of your own...
# The recipe format is documented in the file devel/partman-auto-recipe.txt.
# If you have a way to get a recipe file into the d-i environment, you can
# just point at it.
#d-i partman-auto/expert_recipe_file string /hd-media/recipe
# If not, you can put an entire recipe the preseed file in one (logical)
# line. This example creates a small /boot partition, suitable swap, and
# uses the rest of the space for the root partition:
#d-i partman-auto/expert_recipe string \
# boot-root :: \
# 40 50 100 ext3 \
# $primary{ } $bootable{ } \
# method{ format } format{ } \
# use_filesystem{ } filesystem{ ext3 } \
# mountpoint{ /boot } \
# . \
# 500 10000 1000000000 ext3 \
# method{ format } format{ } \
# use_filesystem{ } filesystem{ ext3 } \
# mountpoint{ / } \
# . \
# 64 512 300% linux-swap \
# method{ swap } format{ } \
# .
# This makes partman automatically partition without confirmation.
d-i partman/confirm_write_new_label boolean true
d-i partman/choose_partition \
select Finish partitioning and write changes to disk
d-i partman/confirm boolean true
B.4.5. Clock and time zone setup
# Controls whether or not the hardware clock is set to UTC.
d-i clock-setup/utc boolean true
# You may set this to any valid setting for $TZ; see the contents of
# /usr/share/zoneinfo/ for valid values.
d-i time/zone string US/Eastern
B.4.6. Apt setup
Setup of the /etc/apt/sources.list and basic configuration options is fully
automated based on your installation method and answers to earlier questions.
Only the two variables below are relevant for preseeding.
# You can choose to install non-free and contrib software.
#d-i apt-setup/non-free boolean true
#d-i apt-setup/contrib boolean true
B.4.7. Account setup
The password for the root account and name and password for a first regular
user's account can be preseeded. For the passwords you can use either clear
text values or MD5 hashes.
Warning
Be aware that preseeding passwords is not completely secure as everyone with
access to the preseed file will have the knowledge of these passwords. Using
MD5 hashes is considered slightly better in terms of security but it might also
give a false sense of security as access to a MD5 hash allows for brute force
attacks.
# Root password, either in clear text
#passwd passwd/root-password password r00tme
#passwd passwd/root-password-again password r00tme
# or encrypted using an MD5 hash.
#passwd passwd/root-password-crypted password [MD5 hash]
# Skip creation of a normal user account.
#passwd passwd/make-user boolean false
# Alternatively, create a normal user account.
#passwd passwd/user-fullname string Debian User
#passwd passwd/username string debian
# Normal user's password, either in clear text
#passwd passwd/user-password password insecure
#passwd passwd/user-password-again password insecure
# or encrypted using an MD5 hash.
#passwd passwd/user-password-crypted password [MD5 hash]
The passwd/root-password-crypted and passwd/user-password-crypted variables can
also be preseeded with "!" as their value. In that case, the corresponding
account is disabled. This may be convenient for the root account, provided of
course that an alternate method is setup to allow administrative activities or
root login (for instance by using SSH key authentication or sudo).
An MD5 hash for a password can be generated using the following command.
$ echo "r00tme" | mkpasswd -s -H MD5
B.4.8. Boot loader installation
# Grub is the default boot loader (for x86). If you want lilo installed
# instead, uncomment this:
#d-i grub-installer/skip boolean true
# This is fairly safe to set, it makes grub install automatically to the MBR
# if no other operating system is detected on the machine.
d-i grub-installer/only_debian boolean true
# This one makes grub-installer install to the MBR if if finds some other OS
# too, which is less safe as it might not be able to boot that other OS.
d-i grub-installer/with_other_os boolean true
# Alternatively, if you want to install to a location other than the mbr,
# uncomment and edit these lines:
#d-i grub-installer/bootdev string (hd0,0)
#d-i grub-installer/only_debian boolean false
#d-i grub-installer/with_other_os boolean false
B.4.9. Finishing up the first stage install
# Avoid that last message about the install being complete.
d-i prebaseconfig/reboot_in_progress note
# This will prevent the installer from ejecting the CD during the reboot,
# which is useful in some situations.
#d-i cdrom-detect/eject boolean false
B.5. Preseeding the second stage of the installation
B.5.1. Base config
# Avoid the introductory message.
base-config base-config/intro note
# Avoid the final message.
base-config base-config/login note
# If you installed a display manager, but don't want to start it immediately
# after base-config finishes.
#base-config base-config/start-display-manager boolean false
# Some versions of the installer can report back on what you've installed.
# The default is not to report back, but sending reports helps the project
# determine what software is most popular and include it on CDs.
#popularity-contest popularity-contest/participate boolean false
B.5.2. Package selection
You can choose to install any combination of tasks that are available.
Available tasks as of this writing include:
* Standard system
* Desktop environment
* Web server
* Print server
* DNS server
* File server
* Mail server
* SQL database
* Laptop
* manual package selection
The last of these will run aptitude. You can also choose to install no tasks,
and force the installation of a set of packages in some other way. We recommend
always including the Standard system task.
tasksel tasksel/first multiselect Standard system, Desktop environment
#tasksel tasksel/first multiselect Standard system, Web server
B.5.3. Mailer configuration
During a normal install, exim asks only a few questions. Here's how to avoid
even those. More complicated preseeding is possible.
exim4-config exim4/dc_eximconfig_configtype \
select no configuration at this time
exim4-config exim4/no_config boolean true
exim4-config exim4/no_config boolean true
exim4-config exim4/dc_postmaster string
B.5.4. X configuration
Preseeding Debian's X config is possible, but you probably need to know some
details about the video hardware of the machine, since Debian's X configurator
does not do fully automatic configuration of everything.
# X can detect the right driver for some cards, but if you're preseeding,
# you override whatever it chooses. Still, vesa will work most places.
#xserver-xfree86 xserver-xfree86/config/device/driver select vesa
# A caveat with mouse autodetection is that if it fails, X will retry it
# over and over. So if it's preseeded to be done, there is a possibility of
# an infinite loop if the mouse is not autodetected.
#xserver-xfree86 xserver-xfree86/autodetect_mouse boolean true
# Monitor autodetection is recommended.
xserver-xfree86 xserver-xfree86/autodetect_monitor boolean true
# Uncomment if you have an LCD display.
#xserver-xfree86 xserver-xfree86/config/monitor/lcd boolean true
# X has three configuration paths for the monitor. Here's how to preseed
# the "medium" path, which is always available. The "simple" path may not
# be available, and the "advanced" path asks too many questions.
xserver-xfree86 xserver-xfree86/config/monitor/selection-method \
select medium
xserver-xfree86 xserver-xfree86/config/monitor/mode-list \
select 1024x768 @ 60 Hz
B.5.5. Preseeding other packages
# Depending on what software you choose to install, or if things go wrong
# during the installation process, it's possible that other questions may
# be asked. You can preseed those too, of course. To get a list of every
# possible question that could be asked during an install, do an
# installation, and then run these commands:
# debconf-get-selections --installer > file
# debconf-get-selections >> file
B.6. Advanced options
B.6.1. Shell commands
# d-i preseeding is inherently not secure. Nothing in the installer checks
# for attempts at buffer overflows or other exploits of the values of a
# preseed file like this one. Only use preseed files from trusted
# locations! To drive that home, and because it's generally useful, here's
# a way to run any shell command you'd like inside the installer,
# automatically.
# This first command is run as early as possible, just after
# preseeding is read.
#d-i preseed/early_command string anna-install some-udeb
# This command is run just before the install finishes, but when there is
# still a usable /target directory.
#d-i preseed/late_command string echo foo > /target/etc/bar
# This command is run just as base-config is starting up.
#base-config base-config/early_command string echo hi mom
# This command is run after base-config is done, just before the login:
# prompt. This is a good way to install a set of packages you want, or to
# tweak the configuration of the system.
#base-config base-config/late_command \
# string apt-get install zsh; chsh -s /bin/zsh
B.6.2. Chainloading preseed files
It is possible to include other preseed files from a preseed file. Any settings
in those files will override pre-existing settings from files loaded earlier.
This makes it possible to put, for example, general networking settings for
your location in one file and more specific settings for certain configurations
in other files.
# More that one file can be listed, separated by spaces; all will be
# loaded. The included files can have preseed/include directives of their
# own as well. Note that if the filenames are relative, they are taken from
# the same directory as the preseed file that includes them.
#d-i preseed/include string x.cfg
# The installer can optionally verify checksums of preseed files before
# using them. Currently only md5sums are supported, list the md5sums
# in the same order as the list of files to include.
#d-i preseed/include/checksum string 5da499872becccfeda2c4872f9171c3d
# More flexibly, this runs a shell command and if it outputs the names of
# preseed files, includes those files.
#d-i preseed/include_command \
# string echo if [ "`hostname`" = bob ]; then echo bob.cfg; fi
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