How to Force YUM to Exclude Certain Packages

YUM is a package management system for Red Hat Enterprise Linux (RHEL), CentOS, Fedora, and other Red Hat-based Linux operating systems. It is command-line driven and is an easy tool you can use to keep your server updated and install any new software you need.

Normally, when you perform updates, YUM will search the distribution’s online repository and select any newly updated packages for download and installation. These may include everything from Apache web server to the Linux kernel itself.

Most of the time, it is a general good practice to update all of the available packages, but there are times when this may not be ideal. For example, if you know for certain that a new version of a particular package that you have installed will not work with a version of one of your web applications, you may want to delay updating until you have patched your application. Another possible scenario is that you may want to update most of your other packages now but wait until later to update the kernel, which will require a reboot.

YUM has a built-in feature that allows you to exclude a package or group of packages of your choosing. You can either use the exclude function on a long-term basis or for one particular update. To make a long-term change, you should edit your repository file (usually yum.conf). Find the [main] section and add the following line:
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How to Schedule a Reboot on a Windows Server

In a previous post, I explained how to use the “at” command to schedule a reboot on a Linux server. On a Windows server, you can accomplish the same thing. Scheduling a reboot is helpful for those rare occasions when you make changes to your server that require a reboot. A major system security update is a perfect example.

In those instances, it is not wise to reboot your server in the middle of the day, at the height of website traffic. By scheduling your reboot, you can minimize the number of website visitors affected by any downtime. Also, if something goes wrong, any extended downtime will be during off hours.

To schedule a reboot, enter the Windows command prompt and run the following command:

c:> at 4:00am c:\admutils\psshutdown.exe -r -f -c -t 10

In this example, the server will reboot at 4:00AM. As with any server, make sure that your system time is correct. Otherwise, you might end up performing the reboot at an inopportune time.

Source: nixCraft
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What to do when your server goes down

First of all: do not panic. What may appear to be an outage, may actually be an issue with your network connection or Internet congestion. Once you have eliminated the usual suspects, there are a few steps you can take to resolve the issue quickly and get your dedicated server back up and running.

1. Test an SSH connection. If you can still SSH into your server, you most likely just have a software issue. If your web server application (such as Apache) has crashed, a simple restart may fix the problem. If you notice it starting to crash routinely every day or every week, you may have a security exploit.

2. If you cannot SSH into your server, try to ping and traceroute the server. If you get network connections all the way up the traceroute but cannot connect to your server, that means the network is fine, but the physical server may have crashed or been shutdown. Follow the normal procedure for rebooting. If your server is remote, you can ask your web host to reboot it. Some hosts also have automatic reboot switches that you can activate remotely. If something is wrong with the network, check with your host. They may already be diligently trying to fix the problem.

3. If rebooting does not fix the problem, and you cannot access your server, your host may offer you a KVM connection so that you can troubleshoot your server’s network settings.

4. If your host cannot even get the server to start in order to use KVM, they will probably have to re-image your box. This will erase everything, and you will be thankful at this point that you have kept backups of all websites on your server.

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99% Uptime Guarantee

It seems as though nearly all web hosting providers promise 99% uptime. Therefore, the promise alone does not make the choice any easier. While there are sites that provide monitoring services that rate the actual uptime of hosts, the real question you should ask a web host is what the guarantee entails.

There is no question that even the best web host will have some down time. That is why no host promises 100% uptime. When your server does go down, what are the consequences? Will the web host say nothing and just eventually turn it back on, pretending like nothing happened? Will they apologize after a reboot? Will they assure you that it will never happen again?

The truth is, when a website is critical to an organization or business, a web host, which is also a business, should compensate the customer for downtime. That guarantee should include a clause about compensation. It may take the form of pro-rating a monthly fee or some other form, but the ultimate outcome should satisfy the customer.

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How to schedule a reboot on a Linux server

Automating tasks in Linux is a pretty straightforward process, mainly because the tool used to do it comes with all Linux distributions. It is called Cron, as we mentioned in an earlier post. Cron allows you to automate all sorts of tasks, including reboots. But if you just need to reboot once at a certain time, “at” might suit you well.

Why would you want to schedule a reboot? Usually, you only need to reboot a Linux server after installing a kernel update. Since you can plan such an update ahead of time, the ideal time to reboot would be when most users are not accessing the server. That time, however, might be when you are asleep.

To use “at”, become root and type “at” followed by the time you want the server to reboot:

# at 4am tuesday

This will start the “at” prompt, where you need to type “reboot”.

at> reboot

Press CTRL+D to save your settings. Now your server will reboot at the specified time.