About the /usr directory
/usr is the core of the linux system, including all shared files.
It is one of the most important directories in the Unix system, covering binary files, various documents, various header files, x, and various library files; there are also many programs, such as ftp, telnet and so on.
/usr is not the abbreviation of user, in fact, usr is the abbreviation of Unix Software Resource, that is, the directory where the software resources of the Unix operating system are placed, rather than user data; all system default software will be placed in /usr, and when the system is installed, This directory will take up the most hard disk capacity.
About /bin /sbin /usr/bin /usr/sbin
bin directory:
bin is the abbreviation of binary and mainly places some necessary execution files of the system, such as: cat, cp, chmod df, dmesg, gzip, kill, ls, mkdir, more, mount, rm, su, tar, etc.
/usr/bin directory:
mainly places the necessary execution files of some application software tools such as c++, g++, gcc, chdrv, diff, dig, du, eject, elm, free, gnome*, zip, htpasswd, kfm, ktop, last , less, locale, m4, make, man, mcopy, ncftp, newaliases, nslookup passwd, quota, smb*, wget, etc.
/sbin directory:
mainly places some necessary programs for system management, such as: cfdisk, dhcpcd, dump, e2fsck, fdisk, halt, ifconfig, ifup, ifdown, init, insmod, lilo, lsmod, mke2fs, modprobe, quotacheck, reboot, rmmod , runlevel, shutdown, etc.
/usr/sbin directory:
place some necessary programs for network management such as: dhcpd, httpd, imap, in.*d, inetd, lpd, named, netconfig, nmbd, samba, sendmail, squid, swap, tcpd, tcpdump, etc.
General
If this is a necessary binary for users and administrators, it will go in /bin. If it is a binary that is necessary for system administrators, but not used by ordinary users at all, it will be placed in /sbin.
Relatively speaking. If it is not a necessary binary file for users, it will probably be placed in /usr/bin; if it is not a necessary tool for system administrators, it will probably be placed in /usr/sbin.