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authorBruce Dubbs <bdubbs@linuxfromscratch.org>2020-06-16 11:56:28 +0000
committerBruce Dubbs <bdubbs@linuxfromscratch.org>2020-06-16 11:56:28 +0000
commit675606bde2ba53946537b42a5aa576692a311621 (patch)
treeaf20c20ce3841c16b24d0b9903af6878a4a0f5a6 /chapter07/createfiles.xml
parent560065f976e371779928dbf8b9428217f3f57331 (diff)
parent1cd59612d00603c9ce773ad821a15d20bc4fa0b7 (diff)
Split Chapter 5 into three separate chapters.
Implement a new method of cross-building the LFS tool chain and other tools to simplify the method of isolating the new system from the original host. This will be the start of LFS-10.0. Move old trunk/BOOK to branches/old-trunk. git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11946 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
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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-tools-createfiles">
+ <?dbhtml filename="createfiles.html"?>
+
+ <title>Creating Essential Files and Symlinks</title>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/etc/passwd">/etc/passwd</primary>
+ </indexterm>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/etc/group">/etc/group</primary>
+ </indexterm>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
+ </indexterm>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
+ </indexterm>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
+ </indexterm>
+
+ <indexterm zone="ch-tools-createfiles">
+ <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
+ </indexterm>
+
+ <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>Create a basic <filename>/etc/hosts</filename> file to be
+ referenced in some test suites, and in one of Perl's configuration files
+ as well:</para>
+
+<screen><userinput>echo "127.0.0.1 localhost $(hostname)" &gt; /etc/hosts</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 revision="sysv"><userinput>cat &gt; /etc/passwd &lt;&lt; "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>
+
+<screen revision="systemd"><userinput>cat &gt; /etc/passwd &lt;&lt; "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
+systemd-bus-proxy:x:72:72:systemd Bus Proxy:/:/bin/false
+systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/bin/false
+systemd-journal-remote:x:74:74:systemd Journal Remote:/:/bin/false
+systemd-journal-upload:x:75:75:systemd Journal Upload:/:/bin/false
+systemd-network:x:76:76:systemd Network Management:/:/bin/false
+systemd-resolve:x:77:77:systemd Resolver:/:/bin/false
+systemd-timesync:x:78:78:systemd Time Synchronization:/:/bin/false
+systemd-coredump:x:79:79:systemd Core Dumper:/:/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>
+ will be set later.</para>
+
+ <para>Create the <filename>/etc/group</filename> file by running the following
+ command:</para>
+
+<screen revision="sysv"><userinput>cat &gt; /etc/group &lt;&lt; "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:
+input:x:24:
+mail:x:34:
+kvm:x:61:
+wheel:x:97:
+nogroup:x:99:
+users:x:999:</literal>
+EOF</userinput></screen>
+
+<screen revision="systemd"><userinput>cat &gt; /etc/group &lt;&lt; "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:
+input:x:24:
+mail:x:34:
+kvm:x:61:
+systemd-bus-proxy:x:72:
+systemd-journal-gateway:x:73:
+systemd-journal-remote:x:74:
+systemd-journal-upload:x:75:
+systemd-network:x:76:
+systemd-resolve:x:77:
+systemd-timesync:x:78:
+systemd-coredump:x:79:
+wheel:x:97:
+nogroup:x:99:
+users:x:999:</literal>
+EOF</userinput></screen>
+
+ <para>The created groups are not part of any standard&mdash;they are groups
+ decided on in part by the requirements of the Udev configuration in Chapter
+ 9, 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://refspecs.linuxfoundation.org/lsb.shtml"/>) only recommends 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>Some tests in <xref linkend="chapter-building-system"/> need a regular
+ user. We add this user here and delete this account at the end of that
+ chapter.</para>
+
+<screen><userinput>echo "tester:x:$(ls -n $(tty) | cut -d" " -f3):101::/home/tester:/bin/bash" &gt;&gt; /etc/passwd
+echo "tester:x:101:" &gt;&gt; /etc/group
+install -o tester -d /home/tester</userinput></screen>
+
+ <para>To remove the <quote>I have no name!</quote> prompt, start a new
+ shell. Since 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 /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 and the next 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,faillog,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/faillog</filename> file records
+ failed login attempts. 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>