Some programs use hard-wired paths to programs which do not exist yet. In order to satisfy these programs, create a number of symbolic links which will be replaced by real files throughout the course of this chapter after the software has been installed:
ln -sv /tools/bin/{bash,cat,echo,grep,pwd,stty} /bin
ln -sv /tools/bin/perl /usr/bin
ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
ln -sv /tools/lib/libstdc++.so{,.6} /usr/lib
ln -sv bash /bin/sh
A proper Linux system maintains a list of the mounted file systems in
the file /etc/mtab. Normally, this file
would be created when we mount a new file system. Since we will not
be mounting any file systems inside our chroot environment, create an
empty file for utilities that expect the presence of /etc/mtab:
touch /etc/mtab
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
nobody:x:99:99:Unprivileged User:/dev/null:/bin/false
EOF
The actual password for root (the
“x” used here is just a
placeholder) will be set later.
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:4:
tape:x:5:
daemon:x:6:
floppy:x:7:
disk:x:8:
lp:x:9:
uucp:x:10:
audio:x:11:
video:x:12:
utmp:x:13:
usb:x:14:
cdrom:x:15:
mail:x:34:
nogroup:x:99:
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
this chapter, 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.
To remove the “I have no
name!” prompt, start a new shell. Since a full Glibc was
installed in Chapter
5 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 this 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/run/utmp /var/log/{btmp,lastlog,wtmp}
chgrp -v utmp /var/run/utmp /var/log/lastlog
chmod -v 664 /var/run/utmp /var/log/lastlog
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.