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94 lines
4.4 KiB
XML
94 lines
4.4 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="ch-partitioning-aboutlfs">
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<?dbhtml filename="aboutlfs.html"?>
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<title>Setting the $LFS Variable and the Umask</title>
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<para>Throughout this book, the environment variable <envar>LFS</envar> will
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be used several times. You should ensure that this variable is always defined
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throughout the LFS build process. It should be set to the name of the
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directory where you will be building your LFS system - we will use
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<filename class="directory">/mnt/lfs</filename> as an example, but you may
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choose any directory name you want. If you are building LFS on a separate
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partition, this directory will be the mount point for the partition.
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Choose a directory location and set the variable with the
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following command:</para>
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<screen role="nodump"><userinput>export LFS=<replaceable>/mnt/lfs</replaceable></userinput></screen>
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<para>Having this variable set is beneficial in that commands such as
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<command>mkdir -v $LFS/tools</command> can be typed literally. The shell
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will automatically replace <quote>$LFS</quote> with
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<quote>/mnt/lfs</quote> (or whatever value the variable was set to) when it
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processes the command line.</para>
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<para>Now set the file mode creation mask (umask) to
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<literal>022</literal> in case the host distro uses a different
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default:</para>
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<screen role="nodump"><userinput>umask 022</userinput></screen>
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<para>Setting the umask to 022 ensures that newly created files and
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directories are only writable by their owner, but are readable and
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searchable (only for directories) by anyone (assuming default modes are
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used by the <ulink role='man' url='&man;open.2'>open(2)</ulink> system
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call, new files will end up with permission mode 644 and directories with
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mode 755). An overly-permissive default can leave security holes in the
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LFS system, and an overly-restrictive default can cause strange issues
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building or using the LFS system.</para>
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<caution>
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<para>Do not forget to check that <envar>LFS</envar> is set and the
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umask is set to <literal>022</literal> whenever
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you leave and reenter the current working environment (such as when doing a
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<command>su</command> to <systemitem class="username">root</systemitem> or
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another user). Check that the <envar>LFS</envar> variable is set up
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properly with:</para>
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<screen role="nodump"><userinput>echo $LFS</userinput></screen>
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<para>Make sure the output shows the path to your LFS system's build
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location, which is <filename class="directory">/mnt/lfs</filename> if the
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provided example was followed.</para>
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<para>Check that the umask is set up properly with:</para>
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<screen role="nodump"><userinput>umask</userinput></screen>
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<para>The output should be <computeroutput>022</computeroutput>.</para>
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<para>If any output of these two commands is incorrect, use the command
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given earlier on this page to set <envar>$LFS</envar> to the correct
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directory name and set umask to <literal>022</literal>.</para></caution>
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<note><para>One way to ensure that the <envar>LFS</envar> variable and the
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umask are always set properly is to edit the
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<filename>.bash_profile</filename> file in both your personal home
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directory and in <filename>/root/.bash_profile</filename> and
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enter the <command>export</command> and <command>umask</command> commands
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above. In addition, the shell specified in the
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<filename>/etc/passwd</filename> file for all users that need the
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<envar>LFS</envar> variable must be bash to ensure that the
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<filename>.bash_profile</filename> file is incorporated as a part of
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the login process.</para>
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<para>Another consideration is the method that is used to log into the
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host system. If logging in through a graphical display manager, the
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user's <filename>.bash_profile</filename> is not normally used when
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a virtual terminal is started. In this case, add the commands to
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the <filename>.bashrc</filename> file for the user and
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<systemitem class="username">root</systemitem>. In addition,
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some distributions use an "if" test, and do not run the remaining <filename>.bashrc</filename>
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instructions for a non-interactive bash invocation. Be sure to place the
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commands ahead of the test for non-interactive use.</para>
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</note>
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</sect1>
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