source: clfs-embedded/BOOK/final-system/common/creatingfiles.xml @ b74d39b

Last change on this file since b74d39b was b74d39b, checked in by Andrew Bradford <andrew@…>, 3 years ago

final-system/creatingfiles: s/Udev/BusyBox/ as we don't use udev

BusyBox? dictates our user and group needs, not udev, we don't use udev.

  • Property mode set to 100644
File size: 8.3 KB
Line 
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
6]>
7
8<sect1 id="ch-final-system-creatingfiles">
9  <?dbhtml filename="creatingfiles.html"?>
10
11  <title>Creating the passwd, group, and log Files</title>
12
13  <indexterm zone="ch-final-system-creatingfiles">
14    <primary sortas="e-/etc/passwd">/etc/passwd</primary>
15  </indexterm>
16
17  <indexterm zone="ch-final-system-creatingfiles">
18    <primary sortas="e-/etc/group">/etc/group</primary>
19  </indexterm>
20
21  <indexterm zone="ch-final-system-creatingfiles">
22    <primary sortas="e-/var/run/utmp">/var/run/utmp</primary>
23  </indexterm>
24
25  <indexterm zone="ch-final-system-creatingfiles">
26    <primary sortas="e-/var/log/btmp">/var/log/btmp</primary>
27  </indexterm>
28
29  <indexterm zone="ch-final-system-creatingfiles">
30    <primary sortas="e-/var/log/lastlog">/var/log/lastlog</primary>
31  </indexterm>
32
33  <indexterm zone="ch-final-system-creatingfiles">
34    <primary sortas="e-/var/log/wtmp">/var/log/wtmp</primary>
35  </indexterm>
36
37  <para>A proper Linux system maintains a list of the mounted file systems in
38  the file <filename>/etc/mtab</filename>.  With the way our embedded system is
39  designed, we will be using a symlink to <filename>/proc/mounts</filename>:</para>
40
41<screen><userinput>ln -svf ../proc/mounts ${CLFS}/targetfs/etc/mtab</userinput></screen>
42 
43  <para>In order for user <systemitem class="username">root</systemitem> to be
44  able to login and for the name <quote>root</quote> to be recognized, there
45  must be relevant entries in the <filename>/etc/passwd</filename> and
46  <filename>/etc/group</filename> files.</para>
47
48  <para>Create the <filename>/etc/passwd</filename> file by running the following
49  command:</para>
50
51<screen><userinput>cat &gt; ${CLFS}/targetfs/etc/passwd &lt;&lt; "EOF"
52<literal>root::0:0:root:/root:/bin/ash</literal>
53EOF</userinput></screen>
54
55  <para>The actual password for <systemitem class="username">root</systemitem>
56  (the <quote>::</quote> used here is just a placeholder and allow you to login
57  with no password) will be set later.</para>
58
59  <variablelist os="b">
60
61    <title>Additional optional users you may want to add:</title>
62
63    <varlistentry>
64      <term><literal>bin:x:1:1:bin:/bin:/bin/false</literal></term>
65      <listitem>
66        <para>Can be useful for compatibility with legacy applications.</para>
67      </listitem>
68    </varlistentry>
69    <varlistentry>
70      <term><literal>daemon:x:2:6:daemon:/sbin:/bin/false</literal></term>
71      <listitem>
72        <para>It is often recommended to use an unprivileged User ID/Group ID
73        for daemons in order to limit their access to the system.</para>
74      </listitem>
75    </varlistentry>
76    <varlistentry>
77      <term><literal>adm:x:3:16:adm:/var/adm:/bin/false</literal></term>
78      <listitem>
79        <para>Was used for programs that performed administrative tasks.</para>
80      </listitem>
81    </varlistentry>
82    <varlistentry>
83      <term><literal>lp:x:10:9:lp:/var/spool/lp:/bin/false</literal></term>
84      <listitem>
85        <para>Used by programs for printing.</para>
86      </listitem>
87    </varlistentry>
88    <varlistentry>
89      <term><literal>mail:x:30:30:mail:/var/mail:/bin/false</literal></term>
90      <listitem>
91        <para>Often used by email programs.</para>
92      </listitem>
93    </varlistentry>
94    <varlistentry>
95      <term><literal>news:x:31:31:news:/var/spool/news:/bin/false</literal></term>
96      <listitem>
97        <para>Often used for network news servers.</para>
98      </listitem>
99    </varlistentry>
100    <varlistentry>
101      <term><literal>uucp:x:32:32:uucp:/var/spool/uucp:/bin/false</literal></term>
102      <listitem>
103        <para>Often used for Unix-to-Unix Copy of files from one server to the next</para>
104      </listitem>
105    </varlistentry>
106    <varlistentry>
107      <term><literal>operator:x:50:0:operator:/root:/bin/ash</literal></term>
108      <listitem>
109        <para>Often used to allow system operators to access the system.</para>
110      </listitem>
111    </varlistentry>
112    <varlistentry>
113      <term><literal>postmaster:x:51:30:postmaster:/var/spool/mail:/bin/false</literal></term>
114      <listitem>
115        <para>Generally used as an account that receives all the information of troubles with the mail server.</para>
116      </listitem>
117    </varlistentry>
118    <varlistentry>
119      <term><literal>nobody:x:65534:65534:nobody:/:/bin/false</literal></term>
120      <listitem>
121        <para>Used by NFS.</para>
122      </listitem>
123    </varlistentry>
124  </variablelist>
125
126  <para>Create the <filename>/etc/group</filename> file by running the following
127  command:</para>
128
129<screen><userinput>cat &gt; ${CLFS}/targetfs/etc/group &lt;&lt; "EOF"
130<literal>root:x:0:
131bin:x:1:
132sys:x:2:
133kmem:x:3:
134tty:x:4:
135tape:x:5:
136daemon:x:6:
137floppy:x:7:
138disk:x:8:
139lp:x:9:
140dialout:x:10:
141audio:x:11:
142video:x:12:
143utmp:x:13:
144usb:x:14:
145cdrom:x:15:</literal>
146EOF</userinput></screen>
147
148  <variablelist os="c">
149
150    <title>Additional optional groups you may want to add</title>
151
152    <varlistentry>
153      <term><literal>adm:x:16:root,adm,daemon</literal></term>
154      <listitem>
155        <para>All users in this group are allowed to do administrative tasks</para>
156      </listitem>
157    </varlistentry>
158    <varlistentry>
159      <term><literal>console:x:17:</literal></term>
160      <listitem>
161        <para>This group has direct access to the console</para>
162      </listitem>
163    </varlistentry>
164    <varlistentry>
165      <term><literal>cdrw:x:18:</literal></term>
166      <listitem>
167        <para>This group is allowed to use the CDRW drive</para>
168      </listitem>
169    </varlistentry>
170    <varlistentry>
171      <term><literal>mail:x:30:mail</literal></term>
172      <listitem>
173        <para>Used by MTAs (Mail Transport Agents)</para>
174      </listitem>
175    </varlistentry>
176    <varlistentry>
177      <term><literal>news:x:31:news</literal></term>
178      <listitem>
179        <para>Used by Network News Servers</para>
180      </listitem>
181    </varlistentry>
182    <varlistentry>
183      <term><literal>uucp:x:32:uucp</literal></term>
184      <listitem>
185        <para>Used by the Unix-to-Unix copy users</para>
186      </listitem>
187    </varlistentry>
188    <varlistentry>
189      <term><literal>users:x:100:</literal></term>
190      <listitem>
191        <para>The default GID used by shadow for new users</para>
192      </listitem>
193    </varlistentry>
194    <varlistentry>
195      <term><literal>nogroup:x:65533:</literal></term>
196      <listitem>
197        <para>This is a default group used by some programs that do not
198        require a group</para>
199      </listitem>
200    </varlistentry>
201    <varlistentry>
202      <term><literal>nobody:x:65534:</literal></term>
203      <listitem>
204        <para>This is used by NFS</para>
205      </listitem>
206    </varlistentry>
207  </variablelist>
208
209  <para>The created groups are not part of any standard&mdash;they are groups
210  decided on in part by the requirements of BusyBox later in this
211  chapter, and in part by common convention employed by a number of existing
212  Linux distributions. The Linux Standard Base (LSB, available at <ulink
213  url="http://www.linuxbase.org"/>) recommends only that, besides the group
214  <systemitem class="groupname">root</systemitem> with a Group ID (GID) of 0,
215  a group <systemitem class="groupname">bin</systemitem> with a GID of 1 be
216  present. All other group names and GIDs can be chosen freely by the system
217  administrator since well-written programs do not depend on GID numbers, but
218  rather use the group's name.</para>
219
220  <para>The <command>login</command>, <command>agetty</command>, and
221  <command>init</command> programs (and others) use a number of log
222  files to record information such as who was logged into the system and
223  when. However, these programs will not write to the log files if they
224  do not already exist. Initialize the log files and give them
225  proper permissions:</para>
226
227<screen><userinput>touch ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/{btmp,lastlog,wtmp}
228chmod -v 664 ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/lastlog</userinput></screen>
229
230  <para>The <filename>/var/run/utmp</filename> file records the users
231  that are currently logged in. The <filename>/var/log/wtmp</filename>
232  file records all logins and logouts. The
233  <filename>/var/log/lastlog</filename> file records when
234  each user last logged in. The <filename>/var/log/btmp</filename> file
235  records the bad login attempts.</para>
236
237</sect1>
Note: See TracBrowser for help on using the repository browser.