📄 settingenvironment.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"><html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content= "application/xhtml+xml; charset=iso-8859-1" /> <title> 4.5. Setting Up the Environment </title> <link rel="stylesheet" href="../stylesheets/lfs.css" type="text/css" /> <meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /> <link rel="stylesheet" href="../stylesheets/lfs-print.css" type= "text/css" media="print" /> </head> <body id="lfs" class="CLFS-SVN-20060417-MIPS"> <div class="navheader"> <div class="headertitles"> <h4> Cross-Compiled Linux From Scratch - Version CLFS-SVN-20060417-MIPS </h4> <h3> Chapter 4. Final Preparations </h3> </div> <ul class="headerlinks"> <li class="prev"> <a accesskey="p" href="addinguser.html" title= "Adding the LFS User">Prev</a> <p> Adding the LFS User </p> </li> <li class="next"> <a accesskey="n" href="abouttestsuites.html" title= "About the Test Suites">Next</a> <p> About the Test Suites </p> </li> <li class="up"> <a accesskey="u" href="chapter.html" title= "Chapter 4. Final Preparations">Up</a>. </li> <li class="home"> <a accesskey="h" href="../index.html" title= "Cross-Compiled Linux From Scratch - Version CLFS-SVN-20060417-MIPS"> Home</a> </li> </ul> </div> <div class="sect1" lang="en" xml:lang="en"> <div class="titlepage"> <h1 class="sect1"> 4.5. Setting Up the Environment </h1> </div> <p> Set up a good working environment by creating two new startup files for the <span><strong class="command">bash</strong></span> shell. While logged in as user <tt class="systemitem">lfs</tt>, issue the following command to create a new <tt class= "filename">.bash_profile</tt>: </p> <pre class="userinput"><kbd class="command">cat > ~/.bash_profile << "EOF"<tt class="literal">exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</tt>EOF</kbd></pre> <p> When logged on as user <tt class="systemitem">lfs</tt>, the initial shell is usually a <span class="emphasis"><em>login</em></span> shell which reads the <tt class="filename">/etc/profile</tt> of the host (probably containing some settings and environment variables) and then <tt class="filename">.bash_profile</tt>. The <span><strong class="command">exec env -i.../bin/bash</strong></span> command in the <tt class="filename">.bash_profile</tt> file replaces the running shell with a new one with a completely empty environment, except for the <tt class="envar">HOME</tt>, <tt class= "envar">TERM</tt>, and <tt class="envar">PS1</tt> variables. This ensures that no unwanted and potentially hazardous environment variables from the host system leak into the build environment. The technique used here achieves the goal of ensuring a clean environment. </p> <p> The new instance of the shell is a <span class= "emphasis"><em>non-login</em></span> shell, which does not read the <tt class="filename">/etc/profile</tt> or <tt class= "filename">.bash_profile</tt> files, but rather reads the <tt class= "filename">.bashrc</tt> file instead. Create the <tt class= "filename">.bashrc</tt> file now: </p> <pre class="userinput"><kbd class="command">cat > ~/.bashrc << "EOF"<tt class="literal">set +humask 022LFS=/mnt/lfsLC_ALL=POSIXPATH=/cross-tools/bin:/bin:/usr/binexport LFS LC_ALL PATH</tt>EOF</kbd></pre> <p> The <span><strong class="command">set +h</strong></span> command turns off <span><strong class="command">bash</strong></span>'s hash function. Hashing is ordinarily a useful feature—<span><strong class="command">bash</strong></span> uses a hash table to remember the full path of executable files to avoid searching the <tt class="envar">PATH</tt> time and again to find the same executable. However, the new tools should be used as soon as they are installed. By switching off the hash function, the shell will always search the <tt class="envar">PATH</tt> when a program is to be run. As such, the shell will find the newly compiled tools in <tt class="filename">$LFS/cross-tools</tt> as soon as they are available without remembering a previous version of the same program in a different location. </p> <p> Setting the user file-creation mask (umask) to 022 ensures that newly created files and directories are only writable by their owner, but are readable and executable by anyone (assuming default modes are used by the open(2) system call, new files will end up with permission mode 644 and directories with mode 755). </p> <p> The <tt class="envar">LFS</tt> variable should be set to the chosen mount point. </p> <p> TO BE REWRITTEN - The <tt class="envar">LC_ALL</tt> variable controls the localization of certain programs, making their messages follow the conventions of a specified country. If the host system uses a version of Glibc older than 2.2.4, having <tt class= "envar">LC_ALL</tt> set to something other than “<span class= "quote">POSIX</span>” or “<span class= "quote">C</span>” (during this chapter) may cause issues if you exit the chroot environment and wish to return later. Setting <tt class="envar">LC_ALL</tt> to “<span class= "quote">POSIX</span>” or “<span class= "quote">C</span>” (the two are equivalent) ensures that everything will work as expected in the chroot environment. </p> <p> By putting <tt class="filename">/cross-tools/bin</tt> ahead of the standard <tt class="envar">PATH</tt>, all the programs installed in <a href="../cross-tools/chapter.html">Constructing Cross-Compile Tools</a> are picked up by the cross-compiler immediately after their installation. This, combined with turning off hashing, limits the risk that old programs are used from the host when building a sane set of cross-compiler tools. </p> <p> Finally, to have the environment fully prepared for building the temporary tools, source the just-created user profile: </p> <pre class="userinput"><kbd class="command">source ~/.bash_profile</kbd></pre> </div> <div class="navfooter"> <ul> <li class="prev"> <a accesskey="p" href="addinguser.html" title= "Adding the LFS User">Prev</a> <p> Adding the LFS User </p> </li> <li class="next"> <a accesskey="n" href="abouttestsuites.html" title= "About the Test Suites">Next</a> <p> About the Test Suites </p> </li> <li class="up"> <a accesskey="u" href="chapter.html" title= "Chapter 4. Final Preparations">Up</a>. </li> <li class="home"> <a accesskey="h" href="../index.html" title= "Cross-Compiled Linux From Scratch - Version CLFS-SVN-20060417-MIPS"> Home</a>. </li> </ul> </div> </body></html>⌨️ 快捷键说明
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