问题2：本地文件系统挂载默认是共享的？ 问题3：文件系统访问控制是在哪一层实现的？ 二、文件系统权限管理 文件类型 文件权限 特殊权限(SUID, SGID, STICKY) 文件默认权限umask 用户&用户组 文件系统用户权限管理 对mode的管理 对ACL（Access Control Lists）的管理 ACL Access Entry保存在哪？ ACL的表示 内存中的ACL 是如何与具体的 permitted 文件默认权限umask 为什么默认创建的目录权限为755，文件为644？ 在linux系统中， ，这些新的文件或目录都会有默认的访问权限 创建一个新的文件或者目录时 umask命令与文件和目录的默认访问权限有关，umask值则表明了需要从默认权限中去掉哪些权限来成 为最终的默认权限值。 root@pubbeta2-curve5:~# umask 0022 权限为777，文件 权限为777，文件为666，经过与umask作用，最终权限为755、644 默认目录 Windows Linux umask /etc/login.defs # UMASK is the default umask value for pam_umask and is used by # useradd and newusers to set the mode of the new home directories

ln gzip gunzip tar alias cat less tail wc grep sort 2 uniq diff echo chown chmod umask du df basename dirname ps top kill killall jobs bg fg type which nohup xargs vim filename 67 umask When you create a file, you don't have to decide permissions up front. Permissions have defaults. Those defaults can be controlled and modified using the umask command. Typing Typing umask with no arguments will show you the current umask, in this case 0022 : What does 0022 mean? That's an octal value that represent the permissions. Another common value is 0002 . Use

less 20. tail 21. wc 22. grep 23. sort 24. uniq 25. diff 26. echo 27. chown 28. chmod 29. umask 30. du 31. df 4 32. basename 33. dirname 34. ps 35. top 36. kill 37. killall 38. jobs 39 filename 29. umask 54 When you create a file, you don't have to decide permissions up front. Permissions have defaults. Those defaults can be controlled and modified using the umask command. Typing Typing umask with no arguments will show you the current umask, in this case 0022 : What does 0022 mean? That's an octal value that represent the permissions. Another common value is 0002 . Use

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: –umask\n\n Effective :manpage:‘umask(1)‘ (in octal) of the process after detaching.\n Inherits the :manpage:‘umask(1)‘ of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: --umask\n\n Effective :manpage:`umask(1)` (in octal) of the process after detaching.\n Inherits the :manpage:`umask(1)` of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: --umask\n\n Effective :manpage:`umask(1)` (in octal) of the process after detaching.\n Inherits the :manpage:`umask(1)` of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: –umask\n\n Effective :manpage:‘umask(1)‘ (in octal) of the process after detaching.\n Inherits the :manpage:‘umask(1)‘ of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: –umask\n\n Effective :manpage:‘umask(1)‘ (in octal) of the process after detaching.\n Inherits the :manpage:‘umask(1)‘ of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: --umask\n\n Effective :manpage:`umask(1)` (in octal) of the process after detaching.\n Inherits the :manpage:`umask(1)` of the parent process by default.\n\n..

group name of the main group to change to after detaching. --umask Effective umask (in octal) of the process after detaching. Inherits the umask of the parent process by default. --workdir Optional directory name of the main group to change to after detaching. --umask Effective umask(1) (in octal) of the process after detaching. Inherits the umask(1) of the parent process by default. --workdir Optional change to after\n detaching.\n\n.. cmdoption:: –umask\n\n Effective :manpage:‘umask(1)‘ (in octal) of the process after detaching.\n Inherits the :manpage:‘umask(1)‘ of the parent process by default.\n\n..