16 Administration Tasks in .NET Writer USS Code 128 in .NET 16 Administration Tasks

How to generate, print barcode using .NET, Java sdk library control with example project source code free download:
576 16 Administration Tasks generate, create barcode 128 none in .net projects QR Code Spevcification lsof: Finds Open Files The lsof (ls open files) utility locates open files. Its options display only certain processes, only certain file descriptors of a process, or only certain network connections (network connections use file descriptors just as normal files do and lsof can show these as well). Once you have identified a suspect process using ps ef, give the following command:.

# lsof -s -p pid Replace pid with t he process ID of the suspect process; lsof displays a list of file descriptors that process pid has open. The s option displays the sizes of all open files. Because the s option accepts an argument, you cannot combine it with p ( sp does not work).

This size information is helpful in determining whether the process has a very large file open. If it does, contact the owner of the process or, if necessary, kill the process. The rn option redisplays the output of lsof every n seconds.

. Keeping a Machine Log A machine log that includes the information shown in Table 16-4 can help you find and fix system problems. Include the time and date for each entry in the log. Avoid the temptation to keep the log only on the computer it will be most useful to you when the system is down.

Another good idea is to keep a record of all email about user problems. One strategy is to save this mail to a separate file or folder as you read it. Another approach is to set up a mail alias that users can send mail to when they have problems.

This alias can then forward mail to you and also store a copy in an archive file. Following is an example of an entry in the /etc/aliases file (page 675) that sets up this type of alias:. trouble: admin,/var/spool/mail/admin.archive Email sent to the trouble alias will be forwarded to the admin user and also stored in the file /var/mail/admin.archive..

Table 16-4. Entry Hardware modifications Machine log Function Keep track of the barcode 128 for .NET system hardware configuration: which devices hold which partitions, the model of the new NIC you added, and so on. Keep track of the options used when building Linux.

Print such files as /usr/src/linux/.config (Linux kernel configuration) and the X11 configuration file /etc/X11/xorg.conf.

The file hierarchy under /etc/sysconfig contains valuable information about network configuration, among other things. Keep as accurate a list as possible of any problems with the system. Make note of any error messages or numbers that the system displays on the system console and identify what users were doing when the problem occurred.

Make a list of all reasonable complaints made by knowledgeable users (for example, machine is abnormally slow ).. System software modifications Hardware malfunctions User complaints Solving Problems 577 Keeping the System Secure No system with dia l-in lines or public access to terminals is absolutely secure. You can make a system as secure as possible by changing the Superuser password frequently and choosing passwords that are difficult to guess. Do not tell anyone who does not absolutely need to know the Superuser password.

You can also encourage system users to choose difficult passwords and to change them periodically. By default, passwords on Fedora/RHEL use MD5 (page 1093) hashing, which makes them more difficult to break than passwords encrypted with DES (page 1046). It makes little difference how well encrypted your password is if you make it easy for someone to find out or guess what it is.

A password that is difficult to guess is one that someone else would not be likely to think you would have chosen. Do not use words from the dictionary (spelled forward or backward); names of relatives, pets, or friends; or words from a foreign language. A good strategy is to choose a couple of short words, include some punctuation (for example, put a ^ between them), mix the case, and replace some of the letters in the words with numbers.

If it were not printed in this book, an example of a good password would be C&yGram5 (candygrams). Ideally you would use a random combination of ASCII characters, but that would be difficult to remember. You can use one of several excellent password-cracking programs to find users who have chosen poor passwords.

These programs work by repeatedly encrypting words from dictionaries, phrases, names, and other sources. If the encrypted password matches the output of the program, then the program has found the password of the user. A program that cracks passwords is crack.

It and many other programs and security tips are available from CERT (, which was originally called the Computer Emergency Response Team.

Specifically look at

Make sure that no one except Superuser can write to files containing programs that are owned by root and run in setuid mode (for example, mail and su). Also make sure that users do not transfer programs that run in setuid mode and are owned by root onto the system by means of mounting tapes or disks. These programs can be used to circumvent system security.

One technique that prevents users from having setuid files is to use the nosuid flag to mount, which you can set in the flags section in the fstab file. Refer to fstab: Keeps Track of Filesystems on page 490. The BIOS in many machines gives you some degree of protection from an unauthorized person modifying the BIOS or rebooting the system.

When you set up the BIOS, look for a section named Security. You can probably add a BIOS password. If you depend on the BIOS password, lock the computer case.

It is usually a simple matter to reset the BIOS password by using a jumper on the motherboard..
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