Historically, Linux maintains a list of the mounted file systems in
the file /etc/mtab
. Modern kernels
maintain this list internally and exposes it to the user via the
/proc
filesystem. To satisfy utilities
that expect the presence of /etc/mtab
,
create the following symbolic link:
ln -sv /proc/self/mounts /etc/mtab
Create a basic /etc/hosts
file to be
referenced in some test suites, and in one of Perl's configuration
files as well:
echo "127.0.0.1 localhost $(hostname)" > /etc/hosts
In order for user root
to be able to
login and for the name “root” to be recognized, there must be
relevant entries in the /etc/passwd
and
/etc/group
files.
Create the /etc/passwd
file by running
the following command:
cat > /etc/passwd << "EOF"
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/dev/null:/bin/false
daemon:x:6:6:Daemon User:/dev/null:/bin/false
messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/bin/false
uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/bin/false
nobody:x:99:99:Unprivileged User:/dev/null:/bin/false
EOF
The actual password for root
will be
set later.
Create the /etc/group
file by running
the following command:
cat > /etc/group << "EOF"
root:x:0:
bin:x:1:daemon
sys:x:2:
kmem:x:3:
tape:x:4:
tty:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
dialout:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
usb:x:14:
cdrom:x:15:
adm:x:16:
messagebus:x:18:
input:x:24:
mail:x:34:
kvm:x:61:
uuidd:x:80:
wheel:x:97:
nogroup:x:99:
users:x:999:
EOF
The created groups are not part of any standard—they are groups
decided on in part by the requirements of the Udev configuration in
Chapter 9, and in part by common convention employed by a number of
existing Linux distributions. In addition, some test suites rely on
specific users or groups. The Linux Standard Base (LSB, available at
http://refspecs.linuxfoundation.org/lsb.shtml)
only recommends that, besides the group root
with a Group ID (GID) of 0, a group
bin
with a GID of 1 be present. All
other group names and GIDs can be chosen freely by the system
administrator since well-written programs do not depend on GID
numbers, but rather use the group's name.
Some tests in Chapter 8 need a regular user. We add this user here and delete this account at the end of that chapter.
echo "tester:x:$(ls -n $(tty) | cut -d" " -f3):101::/home/tester:/bin/bash" >> /etc/passwd echo "tester:x:101:" >> /etc/group install -o tester -d /home/tester
To remove the “I have
no name!” prompt, start a new shell. Since the
/etc/passwd
and /etc/group
files have been created, user name and
group name resolution will now work:
exec /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 this and the next chapter.
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,lastlog,faillog,wtmp} chgrp -v utmp /var/log/lastlog chmod -v 664 /var/log/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/faillog
file
records failed login attempts. The /var/log/btmp
file records the bad login attempts.
The /run/utmp
file records the users
that are currently logged in. This file is created dynamically in
the boot scripts.