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Linux for dummies 6th edition - Leblanc D.A

Leblanc D.A Linux for dummies 6th edition - Wiley publishing , 2005 . - 459 p.
ISBN: 0-7645-7937-1
Download (direct link): linuxfordummies6thed2005.pdf
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1. Choose SessionOConnection Profiles.
The Connection Profiles dialog box opens, as shown in Figure 13-4.
Figure 13-4:
The PenguiNet Connection Profiles dialog box.
272 Part III: Getting Up to Speed with Linux
Figure 13-5:
Your Linux command line in Windows!
2. Click Add to open a new profile.
3. Enter the name for this profile in the Profile Name text box.
4. Enter your Linux box’s IP address in the Host text box.
5. Enter your Linux login name in the Username text box.
You cannot use the root account here. Doing so is terribly bad for security.
6. Enter your Linux login password in the Password text box.
7. Click Connect to make the connection to your Linux machine.
The Host Key Not Found dialog box opens the first time you connect this way. Click Connect and save the host key. You don’t have to do this step again from this Windows machine. Check out Figure 13-5 to see a Linux command-line interface window on a Windows box! (I’m not sure why this default font is so “freehand”; you can change it for all your sessions by choosing FormatOChange Font or per Connection Profile in the Preferences menu by selecting the profile and clicking the Appearance tab.)
0 192.1G8.0.G:22(SSH2t - PencjiiiNel
$ Session Edit View Fonnat Tools Window Help
» • * M ˙ * r r* t ŕ č Ô
The prolans included with the Debian GNU/Linux system are free software; the exact distribution terms for each program are described in the individual files in /usr/share/doc/"/copyright.
Deb i an GNU/L inux comes with ABSOLUTELY NO WARRANTY, to tte extent permitted by appl icable law. deedXAM4LRVNI41 :~$
When you’re finished, type logout at the command line, and your connection closes.
Chapter 13: A Secure Linux Box Is a Happy Linux Box 273
Connecting to your Linux box from another Linux box with SSH
Yes, you can connect from another Linux box, too. This task is a bit less complicated. Open a terminal window (see Chapter 14) and follow these steps:
1. Type ssh username@ipaddress to open the connection.
For example, type ssh dee@ After you do this step, the following text appears:
The auth enticity of host '192 CO 00 CO ('
can't be es tabli shed.
RSA key fingerpri nt is
ed:68:0f :e3 :78:56:c9: : b3:d6:6e :25:86:77:52:a7:66.
Are you sure you wan t to cont inue conn ecting (yes/no)?
2. Type yes and press Enter.
You now see these lines:
Warning: Permanently added '' (RSA) to the list of known hosts. dee@'s password:
3. Enter your login password and press Enter. Now you’re in!
Close the connection by logging out of the account (type logout).
Connecting to your Linux box from a Macintosh running OS X with SSH
The process from a Macintosh is similar to that under Linux. Go to, which opens a command line window for you. Then type
ssh IPaddress
to access the same user account on the remote machine, or type
ssh login@IPaddress
if you want to access the account login instead of the same account you’re using on the Mac.
Software holes
When someone is already in your system — whether or not they’re allowed to be there — you have additional security concerns to keep in mind. One of these involves what software you have on the machine. Believe it or not, each piece of software is a potential security hole. If someone can get a program to crash in just the right way, they can get greater access to your system than they should. That’s a very bad thing!
274 Part III: Getting Up to Speed with Linux
One way to close software holes is to remove all programs you don’t need. You can always add them later, if necessary. How exactly you do this task depends on the package-management scheme your distribution runs:
^ Fedora: You can use yum at the command line or gyum’s Remove tab (see Chapter 12).
^ Knoppix: You run it off CD, so it’s hard to remove anything!
^ Linspire: Open the CLICK and Run client (Chapter 12), click the My Products tab, select the program you want to remove from the list, and then click Uninstall Selected.
^ Mandrake: From the main menu, choose SystemOConfigurationO
PackagingORemove Software. In the dialog box, check the boxes for the programs you want to remove. When you’re ready to proceed, click Remove.
^ SuSE: Choose SystemOYaSTOSoftwareOlnstall And Remove Software. Locate the program you want to remove (see Chapter 12). Installed software has a checkmark next to it. Click the mark until it becomes a trash can and then click Accept.
^ Xandros: Open the Xandros Networks client as discussed in Chapter 12. Choose Installed Applications, browse to the program you want to remove, and click the Remove link.
If it turns out that, as a result of dependencies, you lose other software that you want to keep, make sure to cancel the removal.
Introducing SELinux
SELinux, or Security-Enhanced Linux ( was developed by the National Security Agency (NSA) in the United States to add a new level of security on top of what’s already available in Linux. To use SELinux in your distribution:
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