雷霆山崖

摘要： directory permission(目录权限) same bits, but different semantics from those of files r: can list directory contents w: can add or remove files from a directory x: can enter a directory especially, when the "w" bit is set, anyone can remove anyone's files, how can we prevent this? the &quo 阅读全文

摘要： when a file is newly created, what's this file's default permission? depend on the environment variable "umask" what does it mean? where is it located? (check the file: /etc/profile) check your umask, run $ umask on my system, this will print: 022 what does it mean? what's the 阅读全文

摘要： 在Linux系统中每个普通用户都可以更改自己的密码，这是合理的设置。问题是：用户的信息保存在文件/etc/passwd中，用户的密码保存在文件/etc/shadow中，也就是说用户更改自己密码时是修改了/etc/shadow文件中的加密密码，但是，LOOK——-rw-r--r-- 1 root root 1787 Oct 27 2009 /etc/passwd-r-------- 1 root root 1187 Oct 27 2009 /etc/shadow/etc/passwd文件每个用户都有读权限但是只有root有写权限，/etc/shadow文件只有超级用户root有读写权限，也就是说 阅读全文