%general-entities; ]> /etc/passwd /etc/group /run/utmp /var/log/btmp /var/log/lastlog /var/log/wtmp Historically, Linux maintained a list of the mounted file systems in the file /etc/mtab. Modern kernels maintain this list internally and expose it to the user via the /proc filesystem. To satisfy utilities that expect to find /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: cat > /etc/hosts << EOF 127.0.0.1 localhost $(hostname) ::1 localhost EOF 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:/usr/bin/false daemon:x:6:6:Daemon User:/dev/null:/usr/bin/false messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/usr/bin/false uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/usr/bin/false nobody:x:65534:65534:Unprivileged User:/dev/null:/usr/bin/false EOF cat > /etc/passwd << "EOF" root:x:0:0:root:/root:/bin/bash bin:x:1:1:bin:/dev/null:/usr/bin/false daemon:x:6:6:Daemon User:/dev/null:/usr/bin/false messagebus:x:18:18:D-Bus Message Daemon User:/run/dbus:/usr/bin/false systemd-journal-gateway:x:73:73:systemd Journal Gateway:/:/usr/bin/false systemd-journal-remote:x:74:74:systemd Journal Remote:/:/usr/bin/false systemd-journal-upload:x:75:75:systemd Journal Upload:/:/usr/bin/false systemd-network:x:76:76:systemd Network Management:/:/usr/bin/false systemd-resolve:x:77:77:systemd Resolver:/:/usr/bin/false systemd-timesync:x:78:78:systemd Time Synchronization:/:/usr/bin/false systemd-coredump:x:79:79:systemd Core Dumper:/:/usr/bin/false uuidd:x:80:80:UUID Generation Daemon User:/dev/null:/usr/bin/false systemd-oom:x:81:81:systemd Out Of Memory Daemon:/:/usr/bin/false nobody:x:65534:65534:Unprivileged User:/dev/null:/usr/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: cdrom:x:15: adm:x:16: messagebus:x:18: input:x:24: mail:x:34: kvm:x:61: uuidd:x:80: wheel:x:97: users:x:999: nogroup:x:65534: EOF 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: cdrom:x:15: adm:x:16: messagebus:x:18: systemd-journal:x:23: input:x:24: mail:x:34: kvm:x:61: systemd-journal-gateway:x:73: systemd-journal-remote:x:74: systemd-journal-upload:x:75: systemd-network:x:76: systemd-resolve:x:77: systemd-timesync:x:78: systemd-coredump:x:79: uuidd:x:80: systemd-oom:x:81: wheel:x:97: users:x:999: nogroup:x:65534: 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 conventions 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 ) only recommends that, besides the group root with a Group ID (GID) of 0, a group bin with a GID of 1 be present. The GID of 5 is widely used for the tty group, and the number 5 is also used in systemd /etc/fstab for the devpts filesystem. 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 ID 65534 is used by the kernel for NFS and separate user namespaces for unmapped users and groups (those exist on the NFS server or the parent user namespace, but do not exist on the local machine or in the separate namespace). We assign nobody and nogroup to avoid an unnamed ID. But other distros may treat this ID differently, so any portable program should not depend on this assignment. Some tests in need a regular user. We add this user here and delete this account at the end of that chapter. echo "tester:x:101:101::/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 /usr/bin/bash --login 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. The utmp, wtmp, btmp, and lastlog files use 32-bit integers for timestamps and they'll be fundamentally broken after year 2038. Many packages have stopped using them and other packages are going to stop using them. It is probably best to consider them deprecated.