centos 的/etc/profile配置文件的开头那段英文什么意思？
主要是加粗那句话，是什么意思？在/etc/profile.d里重新建立一个custom.sh作用是什么？
#It's NOT a good idea to change this file unless you know what you
# are doing. It's much better to create a custom.sh shell script in
# /etc/profile.d/ to make custom changes to your environment, as this
# will prevent the need for merging in future updates.
