delete file of user X

find -user luudao -delete

find -user luudao -exec rm {} \;

command called 'yes'

There's a really cool command called 'yes' that was made just for this purpose (automating repetitive prompts). It repeatedly outputs the string you give it, so you can pipe it into the command that's prompting you like so:

Code:

yes n | cp -i -r /foo

And every time cp pauses with a prompt it will be fed an 'n' + newline from yes

List 100 first files

List 100 first files in a directory sorted by time.

ls -cr | head -n 100 (???)
ls -t | head -n 100

Finding duplicate lines in a file

uniq -d file | wc -l

How to use RPM Commands

This section contains an overview of principal modes using with RPM for installing, uninstalling, upgrading, querying, listing, and checking RPM packages on your Linux system. You must be familiar with these RPM commands now because we'll use them often in the continuation of this book. To install a RPM package, use the command:

[root@deep] /#rpm -ivh foo-1.0-2.i386.rpm

Take a note that RPM packages have a file of names like foo-1.0-2.i386.rpm, which include the package name (foo), version (1.0), release (2), and architecture (i386).

To uninstall a RPM package, use the command:

[root@deep] /#rpm -e foo

Notice that we used the package name foo, not the name of the original package file foo-1.0-2.i386.rpm.

To upgrade a RPM package, use the command:

[root@deep] /#rpm -Uvh foo-1.0-2.i386.rpm

With this command, RPM automatically uninstall the old version of foo package and install the new one. Always use rpm -Uvh to install packages, since it works fine even when there are no previous versions of the package installed.

To query a RPM package, use the command:

[root@deep] /#rpm -q foo

This command will print the package name, version, and release number of installed package foo. Use this command to verify that a package is or is not installed on your system.

To display package information, use the command:

[root@deep] /#rpm -qi foo

This command display package information; includes name, version, and description of the installed program. Use this command to get information about the installed package.

To list files in package, use the command:

[root@deep] /#rpm -qlfoo

This command will list all files in a installed RPM package. It works only when the package is already installed on your system.

To check a RPM signature package, use the command:

[root@deep] /#rpm --checksig foo

This command checks the PGP signature of specified package to ensure its integrity and origin. Always use this command first before installing new RPM package on your system. Also, GnuPG or Pgp software must be already installed on your system before you can use this command.

Source: http://www.faqs.org/docs/securing/chap3sec20.html