The four directories are inherited from traditional UNIX filesystem
| path | description |
|---|---|
| /bin | essential command-line binaries such as cat, cp, which are needed to mount /usr or to run in one-user mode. |
| /sbin | essential system binaries which needed to start, maintain and recover the system, eg. mount, unmount, launchd. |
| /usr/ | non-essential command-line binaries, libraries, header files, and other data. |
| /usr/bin | non-essential command-line binaries such as which, whereis. |
| /usr/sbin | Non-essential system binaries such as sshd, sysctl. |
