Let's now create some structure in our LFS file system. Let's create a directory tree. Issuing the following commands will create a more or less standard tree:

mkdir -p /{bin,boot,dev/{pts,shm},etc/opt,home,lib,mnt,proc}
mkdir -p /{root,sbin,srv,tmp,usr/local,var,opt}
mkdir -p /media/{floppy,cdrom}
mkdir /usr/{bin,include,lib,sbin,share,src}
ln -s share/{man,doc,info} /usr
mkdir /usr/share/{doc,info,locale,man}
mkdir /usr/share/{misc,terminfo,zoneinfo}
mkdir /usr/share/man/man{1,2,3,4,5,6,7,8}
mkdir /usr/local/{bin,etc,include,lib,sbin,share,src}
ln -s share/{man,doc,info} /usr/local
mkdir /usr/local/share/{doc,info,locale,man}
mkdir /usr/local/share/{misc,terminfo,zoneinfo}
mkdir /usr/local/share/man/man{1,2,3,4,5,6,7,8}
mkdir /var/{lock,log,mail,run,spool}
mkdir -p /var/{tmp,opt,cache,lib/misc,local}
mkdir /opt/{bin,doc,include,info}
mkdir -p /opt/{lib,man/man{1,2,3,4,5,6,7,8}}

Directories are, by default, created with permission mode 755, but this isn't desirable for all directories. We will make two changes: one to the home directory of root, and another to the directories for temporary files.

chmod 0750 /root
chmod 1777 /tmp /var/tmp

The first mode change ensures that not just anybody can enter the /root directory -- the same as a normal user would do with his or her home directory. The second mode change makes sure that any user can write to the /tmp and /var/tmp directories, but cannot remove other users' files from them. The latter is prohibited by the so-called “sticky bit” -- the highest bit in the 1777 bit mask.