Question

What chmod command would you use to impose the following permissions?

1. on a directory(called dir1) and all its subdirectories such that: the owner would have read, write, and execute; the group would have read and execute; and others would have read(write the command in two ways: using rwx and using numeric value)

2. on file (called file1)such that: the owner would have read and write; the group would have no permissions; and others would have write

(write the command in two ways: using rwx and using numeric value)

3. set the special permission SGID and sticky bit for dir1.(you don't need to change the defined permission in 1)

Starting from the Linux default permissions for file and directories, what umask command would you use to ensure that for all new:

4. directories, the owner would have read, write, and execute; members of the group would have read and execute; and others would have read

5. files, the owner would have read and execute; the group would have read, write, and execute; and others would have execute

Answer 1

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1)

what you really want to do is set the directories to 755 and either leave the files alone or set them to 644. For this, you can use the find command. For example:

To change all the directories to 755 (drwxr-xr-x):

find /opt/lampp/htdocs -type d -exec chmod 755 {} \;

To change all the files to 644 (-rw-r--r--):

find /opt/lampp/htdocs -type f -exec chmod 644 {} \;

2) chmod 640 file1, which means that the owner has read and write permissions, the group has read permissions, and all other user have no rights to the file.

to set a file to permissions on file1 to read _rwxr_____, you would enter chmod 740 file1.

3)

When the SGID bit is set on an executable file, the effective group is set to the group of the file. The process runs with the permissions of the members of the file’s group, rather than the permissions of the person who launched it.

sudo chown root:mary /usr/local/bin/htg

sudo chmod u-s,g+s /usr/local/bin/htg

ls -lh /usr/local/bin/htg

You can see the SGID bit denoted by the “s” in the group permissions.

The Sticky Bit

When you set the sticky bit on a directory, people can only delete files that belong to them within that directory. They can’t delete files that belong to someone else, no matter which combination of file permissions are set on the files.

mkdir shared

sudo chmod o+t shared

ls -lh -d shared

ls -lh -d /tmp

ls -lh -d /var/tmp