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Special Topics
460
18.35
IPV4 settings (
)
• ICMP settings:
♦
and
Turn on (1) or off (0). First ignores of
your host. Second ignores of your
network. Can help tackle denial of service
packet flooding attacks
♦
Set limits for sending ICMP packets to specific
targets, depending on icmp type, i.e. can stop
packet flooding from your host
• There are dozens of other IP and TCP settings
. . . too many to discuss here
• See
for details
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GBdirect Ltd, 2000
www.linuxtraining.co.uk
Special Topics
461
18.36
Special Topics Exercises
1. Configuring LILO
(a) Put a copy of your existing Linux kernel on a floppy, then configure to boot your machine from it. N.B. Do NOT do the next question until you are sure your boot disk works!
(b) Configure to boot your machine from a new Linux kernel on your hard drive.
Ideally you should do this with a distinctively new kernel, such as the one made for the Kernel Internals module, but you could simply copy your current kernel with a new name.
2. Using RPMs
(a) Use from the command line to:
i. Install a package
ii. Update a package
iii. Uninstall a package
(b) If you have a distribution CD available:
i. Find the main directory containing RPMs.
ii. Work out and use the command string to put a complete list of all the packages’ summary information and filenames into a file called
(c) Verify your RPM.
(d) With a colleague, draw up a list of other RPM packages containing files which have probably changed since installation. Verify them.
(e) Imagine you suspect a system break-in has occurred. Use to check: i. Whether such a break-in has occurred
ii. How your files have been affected
(f) Depending on what you have on your system, find out which packages are required to run
or another window manager
3. Building And Installing Applications From Sources (a) Install an application from sources provided, or indicated, by your tutor 4. Using the filesystem
(a) Print (to screen) simple info from on: i. memory usage
ii. cpu usage
(b) Use to get status info on the following processes: i. The shell you are currently working in
ii.
iii.
(c) Use to enable/disable:
i. IP forwarding
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GBdirect Ltd, 2000
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ii. ICMP packet flooding from your host
iii. ICMP packet flooding of your network
(d) Pass parameters to the running kernel to:
i. Increase the maximum number of file handles available ii. Change your hostname
N.B. Change back to your original hostname as soon as you have succeeded. Many other exercises on your course may depend on it.
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GBdirect Ltd, 2000
www.linuxtraining.co.uk
Special Topics
463
18.37
Special Topics Solutions
1. Configuring LILO
(a) Put a boot image on the floppy, then add something like the following to
, before running and rebooting:
(b) Put a boot image in the directory of your hard disk, then add something like the following to
, before running and rebooting:
2. Using RPMs
(a) Use something like the following commands:
i.
ii.
iii.
(b) If you have a distribution CD available:
i. On Red Hat distributions it will usually be
ii.
(c)
(d) Potentially hundreds of correct answers to this one. Dependent on host setup.
On any system, the following files should really have changed:
•
•
•
•
Find out which package these belong to using:
(e)
(f)
3. Building And Installing Applications From Sources There are several possible methods, but the most popular procedure does the following in the source directory:
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4. Using the filesystem
(a)
i.
ii.
(b) Use or to get the appropriate process IDs, then:
(c)
i.
• On:
• Off
ii. See tutor
iii. See tutor
(d) E.g.
i.
!
ii.
• Change:
• Undo:
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GBdirect Ltd, 2000
www.linuxtraining.co.uk