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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!ENTITY % general-entities SYSTEM "../general.ent">
%general-entities;
]>
<sect1 id="ch-system-createfiles">
<?dbhtml filename="createfiles.html"?>
<title>Creating Essential Files and Symlinks</title>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/etc/passwd">/etc/passwd</primary>
</indexterm>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/etc/group">/etc/group</primary>
</indexterm>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
</indexterm>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
</indexterm>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
</indexterm>
<indexterm zone="ch-system-createfiles">
<primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
</indexterm>
<para>Some programs use hard-wired paths to programs which do not exist yet. In
order to satisfy these programs, create a number of symbolic links which will be
replaced by real files throughout the course of this chapter after the software
has been installed:</para>
<screen><userinput>ln -sv /tools/bin/{bash,cat,echo,pwd,stty} /bin
ln -sv /tools/bin/perl /usr/bin
ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
ln -sv /tools/lib/libstdc++.so{,.6} /usr/lib
sed 's/tools/usr/' /tools/lib/libstdc++.la > /usr/lib/libstdc++.la
ln -sv bash /bin/sh</userinput></screen>
<variablelist>
<title>The purpose of each link:</title>
<varlistentry>
<term><parameter><filename>/bin/bash</filename></parameter></term>
<listitem>
<para>Many <command>bash</command> scripts specify
<filename>/bin/bash</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/bin/cat</filename></parameter></term>
<listitem>
<para>This pathname is hard-coded into Glibc's configure script.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/bin/echo</filename></parameter></term>
<listitem>
<para>This is to satisfy one of the tests in Glibc's test suite, which
expects <filename>/bin/echo</filename>.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/bin/pwd</filename></parameter></term>
<listitem>
<para>Some <command>configure</command> scripts, particularly Glibc's,
have this pathname hard-coded.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/bin/stty</filename></parameter></term>
<listitem>
<para>This pathname is hard-coded into Expect, therefore it is needed
for Binutils and GCC test suites to pass.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/usr/bin/perl</filename></parameter></term>
<listitem>
<para>Many Perl scripts hard-code this path to the
<command>perl</command> program.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/usr/lib/libgcc_s.so{,.1}</filename></parameter></term>
<listitem>
<para>Glibc needs this for the pthreads library to work.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/usr/lib/libstdc++{,.6}</filename></parameter></term>
<listitem>
<para>This is needed by several tests in Glibc's test suite, as well as
for C++ support in GMP.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/usr/lib/libstdc++.la</filename></parameter></term>
<listitem>
<para>This prevents a <filename class="directory">/tools</filename>
reference that would otherwise be in
<filename>/usr/lib/libstdc++.la</filename> after GCC is installed.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter><filename>/bin/sh</filename></parameter></term>
<listitem>
<para>Many shell scripts hard-code <filename>/bin/sh</filename>.</para>
</listitem>
</varlistentry>
</variablelist>
<para>Historically, Linux maintains a list of the mounted file systems in the
file <filename>/etc/mtab</filename>. Modern kernels maintain this list
internally and exposes it to the user via the <filename
class="directory">/proc</filename> filesystem. To satisfy utilities that
expect the presence of <filename>/etc/mtab</filename>, create the following
symbolic link:</para>
<screen><userinput>ln -sv /proc/self/mounts /etc/mtab</userinput></screen>
<para>In order for user <systemitem class="username">root</systemitem> to be
able to login and for the name <quote>root</quote> to be recognized, there
must be relevant entries in the <filename>/etc/passwd</filename> and
<filename>/etc/group</filename> files.</para>
<para>Create the <filename>/etc/passwd</filename> file by running the following
command:</para>
<screen><userinput>cat > /etc/passwd << "EOF"
<literal>root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/dev/null:/bin/false
daemon:x:6:6:Daemon User:/dev/null:/bin/false
messagebus:x:18:18:D-Bus Message Daemon User:/var/run/dbus:/bin/false
nobody:x:99:99:Unprivileged User:/dev/null:/bin/false</literal>
EOF</userinput></screen>
<para>The actual password for <systemitem class="username">root</systemitem>
(the <quote>x</quote> used here is just a placeholder) will be set later.</para>
<para>Create the <filename>/etc/group</filename> file by running the following
command:</para>
<screen><userinput>cat > /etc/group << "EOF"
<literal>root:x:0:
bin:x:1:daemon
sys:x:2:
kmem:x:3:
tape:x:4:
tty:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
dialout:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
usb:x:14:
cdrom:x:15:
adm:x:16:
messagebus:x:18:
systemd-journal:x:23:
mail:x:34:
nogroup:x:99:
users:x:999:</literal>
EOF</userinput></screen>
<para>The created groups are not part of any standard—they are groups
decided on in part by the requirements of the Udev configuration in this
chapter, and in part by common convention employed by a number of existing
Linux distributions. In addition, some test suites rely on specific users
or groups. The Linux Standard Base (LSB, available at <ulink
url="http://www.linuxbase.org"/>) recommends only that, besides the group
<systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
present. All other group names and GIDs can be chosen freely by the system
administrator since well-written programs do not depend on GID numbers, but
rather use the group's name.</para>
<para>To remove the <quote>I have no name!</quote> prompt, start a new
shell. Since a full Glibc was installed in <xref
linkend="chapter-temporary-tools"/> and the
<filename>/etc/passwd</filename> and <filename>/etc/group</filename>
files have been created, user name and group name resolution will now
work:</para>
<screen role="nodump"><userinput>exec /tools/bin/bash --login +h</userinput></screen>
<para>Note the use of the <parameter>+h</parameter> directive. This tells
<command>bash</command> not to use its internal path hashing. Without this
directive, <command>bash</command> would remember the paths to binaries it has
executed. To ensure the use of the newly compiled binaries as soon as they are
installed, the <parameter>+h</parameter> directive will be used for the duration
of this chapter.</para>
<para>The <command>login</command>, <command>agetty</command>, and
<command>init</command> programs (and others) use a number of log
files to record information such as who was logged into the system and
when. However, these programs will not write to the log files if they
do not already exist. Initialize the log files and give them
proper permissions:</para>
<screen><userinput>touch /var/log/{btmp,lastlog,wtmp}
chgrp -v utmp /var/log/lastlog
chmod -v 664 /var/log/lastlog
chmod -v 600 /var/log/btmp</userinput></screen>
<para>The <filename>/var/log/wtmp</filename> file records all logins and
logouts. The <filename>/var/log/lastlog</filename> file records when each
user last logged in. The <filename>/var/log/btmp</filename> file records the
bad login attempts.</para>
<note><para>The <filename>/run/utmp</filename> file records the users that
are currently logged in. This file is created dynamically in the boot
scripts.</para></note>
</sect1>
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