1 umask
umask: The
umask command to prevent files with too loose permissions is encapsulated with umask().
Umask can also be used in the code:
NAME
umask - set file mode creation mask
SYNOPSIS
#include <sys/types.h>
#include <sys/stat.h>
mode_t umask(mode_t mask);
2 Change and management of file permissions
NAME
chmod, fchmod, fchmodat - change permissions of a file
SYNOPSIS
#include <sys/stat.h>
int chmod(const char *pathname, mode_t mode);
int fchmod(int fd, mode_t mode);
3 The sticking bit
t bit is now often used to set the t bit for a specific directory, such as the tmp directory
drwxrwxrwt in the root directory. The last bit is the t bit, so that each user's operations on the tmp directory and files in it will be more specialized Up.
mhr@ubuntu:~/work/linux/wenjianxitong/20$
mhr@ubuntu:~/work/linux/wenjianxitong/20$ ls / -l
total 100
drwxr-xr-x 2 root root 4096 Apr 8 22:58 bin
drwxr-xr-x 3 root root 4096 May 1 03:40 boot
drwxrwxr-x 2 root root 4096 Sep 2 2019 cdrom
drwxr-xr-x 18 root root 3980 May 3 08:50 dev
drwxr-xr-x 132 root root 12288 May 3 08:50 etc
drwxr-xr-x 3 root root 4096 Sep 2 2019 home
lrwxrwxrwx 1 root root 33 May 1 03:40 initrd.img -> boot/initrd.img-4.4.0-178-generic
lrwxrwxrwx 1 root root 33 May 1 03:40 initrd.img.old -> boot/initrd.img-4.4.0-177-generic
drwxr-xr-x 22 root root 4096 Sep 2 2019 lib
drwxr-xr-x 2 root root 4096 Apr 8 22:55 lib64
drwx------ 2 root root 16384 Sep 3 2019 lost+found
drwxr-xr-x 4 root root 4096 Sep 2 2019 media
drwxr-xr-x 3 root root 4096 Sep 2 2019 mnt
drwxr-xr-x 2 root root 4096 Sep 2 2019 opt
dr-xr-xr-x 245 root root 0 May 3 08:49 proc
drwx------ 3 root root 4096 Apr 23 05:34 root
drwxr-xr-x 26 root root 820 May 4 19:13 run
drwxr-xr-x 2 root root 12288 Apr 8 22:58 sbin
drwxr-xr-x 2 root root 4096 Apr 8 23:00 snap
drwxr-xr-x 2 root root 4096 Apr 20 2016 srv
dr-xr-xr-x 13 root root 0 May 3 08:49 sys
drwxrwxrwt 12 root root 4096 May 4 19:17 tmp
drwxr-xr-x 11 root root 4096 Apr 20 2016 usr
drwxr-xr-x 14 root root 4096 Apr 20 2016 var
lrwxrwxrwx 1 root root 30 May 1 03:40 vmlinuz -> boot/vmlinuz-4.4.0-178-generic
lrwxrwxrwx 1 root root 30 May 1 03:40 vmlinuz.old -> boot/vmlinuz-4.4.0-177-generic
mhr@ubuntu:~/work/linux/wenjianxitong/20$
4 File system: FAT UFS
file system: storage and management of files or data
To be added...