Cross-Compiled Linux From Scratch - Version 1.2.0-RC1-Sparc64-Pure64

Chapter 7. If You Are Going to Boot

7.10. Creating the passwd, group, and log Files

In order for user root to be able to login and for the name “root” to be recognized, there must be relevant entries in the /etc/passwd and /etc/group files.

Create the ${CLFS}/etc/passwd file by running the following command:

cat > ${CLFS}/etc/passwd << "EOF"
root::0:0:root:/root:/bin/bash
EOF

The actual password for root (the “::” used here is just a placeholder and allows you to login with no password) will be set later.

Additional users you may want to add:

bin:x:1:1:bin:/bin:/bin/false

Can be useful for compatibility with legacy applications.

daemon:x:2:6:daemon:/sbin:/bin/false

It is often recommended to use an unprivileged User ID/Group ID for daemons to run as, in order to limit their access to the system.

adm:x:3:16:adm:/var/adm:/bin/false

Was used for programs that performed administrative tasks.

lp:x:10:9:lp:/var/spool/lp:/bin/false

Used by programs for printing

mail:x:30:30:mail:/var/mail:/bin/false

Often used by email programs

news:x:31:31:news:/var/spool/news:/bin/false

Often used for network news servers

operator:x:50:0:operator:/root:/bin/bash

Often used to allow system operators to access the system

postmaster:x:51:30:postmaster:/var/spool/mail:/bin/false

Generally used as an account that receives all the information of troubles with the mail server

nobody:x:65534:65534:nobody:/:/bin/false

Used by NFS

Create the ${CLFS}/etc/group file by running the following command:

cat > ${CLFS}/etc/group << "EOF"
root:x:0:
bin:x:1:
sys:x:2:
kmem:x:3:
tty:x:4:
tape: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:
EOF

Additional groups you may want to add

adm:x:16:root,adm,daemon

All users in this group are allowed to do administrative tasks

console:x:17:

This group has direct access to the console

cdrw:x:18:

This group is allowed to use the CDRW drive

mail:x:30:mail

Used by MTAs (Mail Transport Agents)

news:x:31:news

Used by Network News Servers

users:x:1000:

The default GID used by shadow for new users

nogroup:x:65533:

This is a default group used by some programs that do not require a group

nobody:x:65534:

This is used by NFS

The created groups are not part of any standard—they are groups decided on in part by the requirements of the Udev configuration in the final system, and in part by common convention employed by a number of existing Linux distributions. The Linux Standard Base (LSB, available at http://www.linuxbase.org) recommends only that, besides the group “root” with a Group ID (GID) of 0, a group “bin” 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.

The login, agetty, and init 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:

touch ${CLFS}/var/run/utmp ${CLFS}/var/log/{btmp,lastlog,wtmp}
chmod -v 664 ${CLFS}/var/run/utmp ${CLFS}/var/log/lastlog
chmod -v 600 ${CLFS}/var/log/btmp

The /var/run/utmp file records the users that are currently logged in. The /var/log/wtmp file records all logins and logouts. The /var/log/lastlog file records when each user last logged in. The /var/log/btmp file records the bad login attempts.