Linux uses su to switch User tips authentication failure solution & copy files when reported cp:omitting directory ' XXX '

Linux uses su to switch User tips authentication Failure Solution:
This problem arises because the Ubtun system does not activate the root user by default and requires us to do this manually, either in the command line interface or in the terminal by entering the following command:

sudo passwd

Password: Your current password

Enter New UNIX Password: This is the root password
Retype new UNIX Password: duplicate root password
You will then be prompted for successful information.

In the note, using Su and sudo is different, using the SU Switch user needs to enter the user's password to switch to, while using sudo is the current user's password.

cp:omitting directory ' XXX ' when Linux files are copied
(2012-11-30 16:32:59)
Reproduced
Label:
Zatan
Category: Project summary
Today, with the Linux command for file copying, an error occurred: Linux cp:omitting directory ' BBS ' (at the time I was using "Cp-i bbs/opt/workspace/apache-tomcat-6.0.35/ WebApps "This command, parameters with-i), because I have just used Linux this thing, so also not too familiar with, went to check the next, originally, this error is because I want to copy the BBS folder directory, there are sub-directory files, so Linux does not allow direct replication, But must be the BBS directory in the subdirectory of all the files to be copied in the past only line: "Cp-r bbs/opt/workspace/apache-tomcat-6.0.35/webapps/" here,-I to replace-R only line!!!
Similarly, if you encounter, to delete a directory file, you must also use the-r command option: Rm-r BBS
You can tell from here that the-r option means recursion.

Linux uses su to switch User tips authentication failure solution & copy files when reported cp:omitting directory ' XXX '