bin目录区别

https://php-osx.liip.ch/

Why are there so many places to put a binary in Linux? There are at least these five:

/bin/
/sbin/
/usr/bin/
/usr/local/bin/
/usr/local/sbin/

/bin (and /sbin) were intended for programs that needed to be on a small / partition before the larger /usr, etc. partitions were mounted. These days, it mostly serves as a standard location for key programs like /bin/sh, although the original intent may still be relevant for e.g. installations on small embedded devices.

/sbin, as distinct from /bin, is for system management programs (not normally used by ordinary users) needed before /usr is mounted.

/usr/bin is for distribution-managed normal user programs.

There is a /usr/sbin with the same relationship to /usr/bin as /sbin has to /bin.

/usr/local/bin is for normal user programs not managed by the distribution package manager, e.g. locally compiled packages. You should not install them into /usr/bin because future distribution upgrades may modify or delete them without warning.

/usr/local/sbin, as you can probably guess at this point, is to /usr/local/bin as /usr/sbin to /usr/bin.

https://unix.stackexchange.com/questions/8656/usr-bin-vs-usr-local-bin-on-linux

/usr/bin下面的都是系统预装的可执行程序，会随着系统升级而改变。
/usr/local/bin目录是给用户放置自己的可执行程序的地方，推荐放在这里，不会被系统升级而覆盖同名文件。

如果两个目录下有相同的可执行程序，谁优先执行受到PATH环境变量的影响，比如我的一台服务器的PATH变量为。
echo $PATH

/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

/usr/lib64/qt-3.3/bin:/usr/local/bin:/bin:/usr/bin:/usr/local/sbin:/usr/sbin:/sbin:/home/dean/bin
这里/usr/local/bin优先于/usr/bin, 一般都是如此。

新版本mac 修改/usr/bin下的文件，提示operation not permitted
但是我们在对 usr/bin 目录下的文件进行操作的时候往往会出现这样的错误

operation not permitted
这是因为一些mac用户在升级系统之后，电脑启用了SIP（System Integrity Protection），增加了rootless机制，导致即使在root权限下依然无法修改文件，在必要时候为了能够修改下面的文件，我们只能关闭该保护机制

1）重启，过程中按住 command+R，进入保护模式

2）打开terminal终端，输入

1
csrutil disable
3）再次重启，即可对 usr/bin 目录下文件进行修改

PS：如果要恢复保护机制，重新进入保护模式，输入

1
csrutil enable