8.7. 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 /etc/passwd file by running the following command:

cat > /etc/passwd << "EOF"
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:/bin:/bin/false
daemon:x:2:6:/sbin:/bin/false
messagebus:x:27:27:D-Bus Message Daemon User:/dev/null:/bin/false
nobody:x:65534:65533:Unprivileged User:/dev/null:/bin/false
EOF

The actual password for root (the “x” used here is just a placeholder) will be set later.

Additional users you may want to add if not already included:

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

messagebus:x:27:27:D-Bus Message Daemon User:/dev/null:/bin/false

Used by the D-Bus systemwide message bus

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

Create the /etc/group file by running the following command:

cat > /etc/group << "EOF"
root:x:0:
bin:x:1:
sys:x:2:
kmem:x:3:
tty:x:5:
tape:x:4:
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:27:
mail:x:30:
wheel:x:39:
nogroup:x:65533:
EOF

Additional groups you may want to add if not already included:

console:x:17:

This group has direct access to the console

cdrw:x:18:

This group is allowed to use the CDRW drive

messagebus:x:27:

User for D-Bus

news:x:31:news

Used by Network News Servers

users:x:1000:

The default GID used by shadow for new users

nobody:x:65533:

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 Systemd 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.linuxfoundation.org/collaborate/workgroups/lsb) 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 /var/log/{btmp,faillog,lastlog,wtmp}
chgrp -v utmp /var/log/{faillog,lastlog}
chmod -v 664 /var/log/{faillog,lastlog}
chmod -v 600 /var/log/btmp

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.

To remove the “I have no name!” prompt, start a new shell. Since a full Glibc was installed in Constructing Cross-Compile Tools and the /etc/passwd and /etc/group files have been created, user name and group name resolution will now work.

exec /tools/bin/bash --login +h

Note the use of the +h directive. This tells bash not to use its internal path hashing. Without this directive, bash 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 +h directive will be used for the duration of the next chapters.