%general-entities; ]> /etc/passwd /etc/group /var/run/utmp /var/log/btmp /var/log/lastlog /var/log/wtmp A proper Linux system maintains a list of the mounted file systems in the file /etc/mtab. With the way our embedded system is designed, we will be using a symlink to /proc/mounts: ln -svf ../proc/mounts ${CLFS}/targetfs/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 > ${CLFS}/targetfs/etc/passwd << "EOF" root::0:0:root:/root:/bin/ash EOF The actual password for root (the :: used here is just a placeholder and allow you to login with no password) will be set later. 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 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. uucp:x:32:32:uucp:/var/spool/uucp:/bin/false Often used for Unix-to-Unix Copy of files from one server to the next operator:x:50:0:operator:/root:/bin/ash 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 /etc/group file by running the following command: cat > ${CLFS}/targetfs/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 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 uucp:x:32:uucp Used by the Unix-to-Unix copy users users:x:100: 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 BusyBox later in this chapter, and in part by common convention employed by a number of existing Linux distributions. The Linux Standard Base (LSB, available at ) 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}/targetfs/var/run/utmp ${CLFS}/targetfs/var/log/{btmp,lastlog,wtmp} chmod -v 664 ${CLFS}/targetfs/var/run/utmp ${CLFS}/targetfs/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.