mirror of https://github.com/tLDP/LDP
253 lines
9.3 KiB
XML
253 lines
9.3 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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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-system-createfiles">
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<?dbhtml filename="createfiles.html"?>
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<title>Creating Essential Files and Symlinks</title>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/etc/passwd">/etc/passwd</primary>
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</indexterm>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/etc/group">/etc/group</primary>
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</indexterm>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
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</indexterm>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
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</indexterm>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
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</indexterm>
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<indexterm zone="ch-system-createfiles">
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<primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
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</indexterm>
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<para>Some programs use hard-wired paths to programs which do not exist yet. In
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order to satisfy these programs, create a number of symbolic links which will be
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replaced by real files throughout the course of this chapter after the software
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has been installed:</para>
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<screen><userinput>ln -sv /tools/bin/{bash,cat,echo,pwd,stty} /bin
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ln -sv /tools/bin/perl /usr/bin
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ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
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ln -sv /tools/lib/libstdc++.so{,.6} /usr/lib
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sed 's/tools/usr/' /tools/lib/libstdc++.la > /usr/lib/libstdc++.la
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ln -sv bash /bin/sh</userinput></screen>
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<variablelist>
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<title>The purpose of each link:</title>
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<varlistentry>
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<term><parameter><filename>/bin/bash</filename></parameter></term>
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<listitem>
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<para>Many <command>bash</command> scripts specify
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<filename>/bin/bash</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/bin/cat</filename></parameter></term>
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<listitem>
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<para>This pathname is hard-coded into Glibc's configure script.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/bin/echo</filename></parameter></term>
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<listitem>
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<para>This is to satisfy one of the tests in Glibc's test suite, which
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expects <filename>/bin/echo</filename>.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/bin/pwd</filename></parameter></term>
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<listitem>
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<para>Some <command>configure</command> scripts, particularly Glibc's,
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have this pathname hard-coded.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/bin/stty</filename></parameter></term>
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<listitem>
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<para>This pathname is hard-coded into Expect, therefore it is needed
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for Binutils and GCC test suites to pass.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/usr/bin/perl</filename></parameter></term>
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<listitem>
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<para>Many Perl scripts hard-code this path to the
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<command>perl</command> program.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/usr/lib/libgcc_s.so{,.1}</filename></parameter></term>
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<listitem>
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<para>Glibc needs this for the pthreads library to work.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/usr/lib/libstdc++{,.6}</filename></parameter></term>
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<listitem>
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<para>This is needed by several tests in Glibc's test suite, as well as
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for C++ support in GMP.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/usr/lib/libstdc++.la</filename></parameter></term>
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<listitem>
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<para>This prevents a <filename class="directory">/tools</filename>
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reference that would otherwise be in
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<filename>/usr/lib/libstdc++.la</filename> after GCC is installed.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter><filename>/bin/sh</filename></parameter></term>
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<listitem>
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<para>Many shell scripts hard-code <filename>/bin/sh</filename>.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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<para>Historically, Linux maintains a list of the mounted file systems in the
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file <filename>/etc/mtab</filename>. Modern kernels maintain this list
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internally and exposes it to the user via the <filename
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class="directory">/proc</filename> filesystem. To satisfy utilities that
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expect the presence of <filename>/etc/mtab</filename>, create the following
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symbolic link:</para>
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<screen><userinput>ln -sv /proc/self/mounts /etc/mtab</userinput></screen>
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<para>In order for user <systemitem class="username">root</systemitem> to be
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able to login and for the name <quote>root</quote> to be recognized, there
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must be relevant entries in the <filename>/etc/passwd</filename> and
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<filename>/etc/group</filename> files.</para>
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<para>Create the <filename>/etc/passwd</filename> file by running the following
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command:</para>
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<screen><userinput>cat > /etc/passwd << "EOF"
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<literal>root:x:0:0:root:/root:/bin/bash
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bin:x:1:1:bin:/dev/null:/bin/false
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daemon:x:6:6:Daemon User:/dev/null:/bin/false
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messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
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systemd-bus-proxy:x:72:72:systemd Bus Proxy:/:/bin/false
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systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/bin/false
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systemd-journal-remote:x:74:74:systemd Journal Remote:/:/bin/false
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systemd-journal-upload:x:75:75:systemd Journal Upload:/:/bin/false
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systemd-network:x:76:76:systemd Network Management:/:/bin/false
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systemd-resolve:x:77:77:systemd Resolver:/:/bin/false
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systemd-timesync:x:78:78:systemd Time Synchronization:/:/bin/false
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nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
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EOF</userinput></screen>
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<para>The actual password for <systemitem class="username">root</systemitem>
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(the <quote>x</quote> used here is just a placeholder) will be set later.</para>
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<para>Create the <filename>/etc/group</filename> file by running the following
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command:</para>
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<screen><userinput>cat > /etc/group << "EOF"
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<literal>root:x:0:
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bin:x:1:daemon
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sys:x:2:
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kmem:x:3:
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tape:x:4:
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tty:x:5:
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daemon:x:6:
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floppy:x:7:
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disk:x:8:
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lp:x:9:
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dialout:x:10:
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audio:x:11:
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video:x:12:
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utmp:x:13:
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usb:x:14:
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cdrom:x:15:
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adm:x:16:
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messagebus:x:18:
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systemd-journal:x:23:
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input:x:24:
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mail:x:34:
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systemd-bus-proxy:x:72:
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systemd-journal-gateway:x:73:
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systemd-journal-remote:x:74:
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systemd-journal-upload:x:75:
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systemd-network:x:76:
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systemd-resolve:x:77:
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systemd-timesync:x:78:
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nogroup:x:99:
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users:x:999:</literal>
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EOF</userinput></screen>
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<para>The created groups are not part of any standard—they are groups
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decided on in part by the requirements of the Udev configuration in this
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chapter, and in part by common convention employed by a number of existing
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Linux distributions. In addition, some test suites rely on specific users
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or groups. The Linux Standard Base (LSB, available at <ulink
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url="http://www.linuxbase.org"/>) recommends only that, besides the group
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<systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
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a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
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present. All other group names and GIDs can be chosen freely by the system
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administrator since well-written programs do not depend on GID numbers, but
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rather use the group's name.</para>
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<para>To remove the <quote>I have no name!</quote> prompt, start a new
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shell. Since a full Glibc was installed in <xref
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linkend="chapter-temporary-tools"/> and the
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<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
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files have been created, user name and group name resolution will now
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work:</para>
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<screen role="nodump"><userinput>exec /tools/bin/bash --login +h</userinput></screen>
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<para>Note the use of the <parameter>+h</parameter> directive. This tells
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<command>bash</command> not to use its internal path hashing. Without this
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directive, <command>bash</command> would remember the paths to binaries it has
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executed. To ensure the use of the newly compiled binaries as soon as they are
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installed, the <parameter>+h</parameter> directive will be used for the duration
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of this chapter.</para>
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<para>The <command>login</command>, <command>agetty</command>, and
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<command>init</command> programs (and others) use a number of log
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files to record information such as who was logged into the system and
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when. However, these programs will not write to the log files if they
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do not already exist. Initialize the log files and give them
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proper permissions:</para>
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<screen><userinput>touch /var/log/{btmp,lastlog,wtmp}
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chgrp -v utmp /var/log/lastlog
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chmod -v 664 /var/log/lastlog
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chmod -v 600 /var/log/btmp</userinput></screen>
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<para>The <filename>/var/log/wtmp</filename> file records all logins and
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logouts. The <filename>/var/log/lastlog</filename> file records when each
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user last logged in. The <filename>/var/log/btmp</filename> file records the
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bad login attempts.</para>
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<note><para>The <filename>/run/utmp</filename> file records the users that
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are currently logged in. This file is created dynamically in the boot
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scripts.</para></note>
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</sect1>
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