Linux Tutorial

Scheduling in Linux…

Linux comes equipped with scheduling tools. Tools that will let you get a full night’s rest and still have that backup program automatically run at 3am on the dot, and even send us an email letting us know about any appointments.

1. Using the at utility

The at command is used for jobs that need to be run only once. at is an interactive program and it takes in an argument, which is the time and date that you want the job to be run. All outputs of at are sent by email. So let’s say it’s 1pm, and we have a meeting at 3pm. In order to be reminded of this meeting at 2:30pm, we can type:

How do you know if someone is probing your network?  Logs are a great place to start, especially your FW-1 logs.  Unfortunately, those logs can be difficult and time consuming to sift through (especially if you are logging 400+ B every day). Wouldn’t it be great if there was an automated method of alerting you?

There are a variety of different probes and attacks black-hats will attempt. he types we will be focusing on is port scans. Port scans are where an individual attempt to connect to a variety of ports to identify what services a system is running.  The scans can be used on a specific target or used to scan entire IP ranges, often chosen at random.  This is one of the most popular information gathering methods used by black-hats today as it identifies what ports and services are open.

There are two types of filesystems you will need to learn how to make in order to get your Linux multi-partition system up and running are swap and ext2.

–Creating a swap filesystem–

The command for this is mkswap. You have to be root to run this, of course. If you get a “command not found” error, then you need to enter the full path, which is: /sbin/mkswap

The options for mkswapare (ripped from the man page):

We will use only anonymous ftp and will not allow any non-anonymous user any access. Here we describe the anonymous ftp server setup that allows anonymous uploads. Any self-respecting guide on the subject will tell you that “this is a bad thing”. But how is it worse than allowing users to FTP from untrusted location and transfer their passwords in clear text? Not everybody (especially, using Windows) can easily setup an FTP tunnel via ssh.

If you want to have your website have user/password restrictions, you must have Apache installed and running. There are only 2 steps to this:

1. create a file with user names and passwords
2. tell the server what you want to be protected and which users are allowed

For the first step, you will use the program htpasswd. It creates a user file and can add or modify users. For security reasons, you should not create the file under the root directory. For example, made it under /usr/local/etc/httpd/ and will use this to show examples. To create a new user file and add the username “xyz” with  the password “abc123” to the file /usr/local/etc/httpd/users: