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If a preconfiguration file cannot be used to preseed some steps, the install can still be fully automated, since you can pass preseed values on the command line when booting the installer.
Boot parameters can also be used if you do not really want to use preseeding, but just want to provide an answer for a specific question. Some examples where this can be useful are documented elsewhere in this manual.
To set a value to be used inside debian-installer, just pass path/to/variable=value for any of the preseed variables listed in the examples in this appendix. If a value is to be used to con- figure packages for the target system, you will need to prepend the owner1 of the variable as in owner:path/to/variable=value. If you don’t specify the owner, the value for the variable will not be copied to the debconf database in the target system and thus remain unused during the configuration of the relevant package.
Normally, preseeding a question in this way will mean that the question will not be asked. To set a specific default value for a question, but still have the question asked, use “?=” instead of “=” as operator. See also Section B.5.2.
Note that some variables that are frequently set at the boot prompt have a shorter alias. If an alias is available, it is used in the examples in this appendix instead of the full variable. The preseed/url variable for example has been aliased as url. Another example is the tasks alias, which translates to tasksel:tasksel/first.
A “---” in the boot options has special meaning. Kernel parameters that appear after the last “---” may be copied into the bootloader configuration for the installed system (if supported by the installer for the bootloader). The installer will automatically filter out any options (like preconfiguration options) that it recognizes.
Note: Current linux kernels (2.6.9 and later) accept a maximum of 32 command line options and 32 environment options, including any options added by default for the installer. If these numbers are exceeded, the kernel will panic (crash). (For earlier kernels, these numbers were lower.)
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.