File and directory permissions on Linux systems

File or directory permissions under Linux 1.1 Description of permissions

1, Linux file or directory permissions are controlled by 9 permissions, every three bits for a group, that is, the file is the main (owner= owner = user) R, W, x, user group (group= group = family) R, W, X; others (other= = not in the same group) R, W, X;

2. Permission Group description

3, R=read=4=cat; W=write=2=echo x=exexute=1 '-' = no permission;

Special permissions: T, T, S, s, x, X, +, etc.;

4, which user creates the file its user or the owner is who, the file group is the user or the user group;

5, users, groups, permissions are relative to the file or directory;

1.2 Creating a simulated environment 1.2.1 test preparation

Groupadd incahome = Create a group that is a home for users and files under root;

Useradd oldboy-g incahome = Add users to the Incahome group;

Useradd oldgirl-g Incahome = = Add users to the Incahome group;

Useradd test = Create a user outside the group

If the Oldboy user exists, execute the following command:

Usermod g Incahome Oldboy

ID Oldboy???

uid=500 (Oldboy) gid=500 (Oldboy) group =500 (Oldboy)

ID Oldgirl

uid=509 (Oldgirl) gid=508 (incahome) group =508 (Incahome)

ID Test

uid=504 (test) gid=504 (test) group =504 (test)

1.2.2 File Creation Test preparation

Mkdir/oldboy = = = created under root

echo "Echo oldboylinux." >/oldboy/test.sh Create a file under root, the user and group of the file are root

Ls-l/oldboy/test.sh

chmod +x/oldboy/test.sh = Give script file permission to execute;

Test One:

Open root, Oldboy, Oldgirl, test user-clone tag--su-user or logout re-login

Ls-l/oldboy/test.sh ===send to four session boxes logout

-rwxr-xr-x

Conclusion One:

Oldboy, Oldgirl, and test are other outsiders for the root user or root group (home), so three users see the third permission, R and X, that cannot be written

Test Two:

Chown oldboy.incahome/oldboy/test.sh = = = Let Oldboy become the owner of the file, incahome become the home or group of the file

Ls-l/oldboy/test.shtxt = = = under Oldboy user

-rwxr-xr-x 1 Oldboy incahome .../oldboy/test.sh

Conclusion: The user = owner of the Oldboy has R, W, X

Ls-l/oldboy/test.sh = = under Oldgirl user

-rwxr-xr-x 1 Oldboy incahome .../oldboy/test.sh

Conclusion: Oldgirl users have R and X, can not W, with the owner of the file Oldboy the same group, is the user group = family

Ls-l/oldboy.txt = = = under test user

-rwxr-xr-x 1 Oldboy incahome .../oldboy/test.sh

Conclusion: Test=other, same as user group Oldgirl permissions, R and X, cannot w

File and directory permissions on Linux systems