setuid 和setgid
linux permissions
ls -l results in the second column -rw xr-x rx time users in the group file name
r read读
w write 写
x execution
For files in terms of:
r read the contents of the file
w modify the contents of the file, delete the file has nothing to do w
x execute permission. File itself must be performed, with the need to r
For directory terms:
r browse the contents of the directory permissions required x coordinate
W Create a directory permissions to delete files, and file
x directory access rights
umask: a command control linux system default permissions
file 644
you 755
How to calculate the default permissions for the new umask, files and directories
Contents: 777-umask =
file:
Each bit of both even umask case, 666-umask