If your server is unavailable, this can mean several things:
- Server operating system failure – error in basic configuration, network settings
- Exhaustion of system resources – insufficient RAM, CPU overload, insufficient disk space
- Server app/service problem
- Technical failure – e.g. a network problem, hardware failure, virtualization error (i.e. problems on our part)
- An attack on the server by an attacker
- Other causes – e.g. an unpaid service, planned outage, etc.
The general troubleshooting procedure (Linux):
- connect to the server using SSH
- check if the RAM is full, the CPU load, I / O load, whether all necessary services are running, etc. (ps, top and iotop tools)
- view system logs and logs of individual applications (usually in the /var/log directory)
- if the server is not available via ping or SSH, check the status of the service in the customer administration
- if you cannot reach the server and the service is active, use KVM to access the server
- if the server does not respond, you can forcibly restart it via the customer administration
- if you are unable to start the server and you have a backup of your data, you can restore it from a backup or reinstall it and then reload the data
Server OS Failure
The VPS operating system itself may have a problem.
- A non-starting server, for example, after an update– an error may have occurred while updating the kernel version – can be detected and resolved via KVM
- Network setup error – the server is working but not available over IP – can be detected and resolved via KVM
- Kernel panic – i.e. the crashing of the operating system in a non-standard situation – you can find out via KVM, solve it by hard reset, or by running another (older) kernel
Some error messages can indicate a site failure, which can be caused by an infection, a setup error, or an incomplete update. Otherwise, the server may be running fine.
System Resource Exhaustion
Dedicated and virtual servers do not have unlimited performance – running your operating system and all other applications and services consumes certain resources – RAM, CPU performance and hard disk space.
As a result of these resources being exhausted, the following may happen:
- the operating system crashes (“freezes”)
- the system is overloaded – it works, but it is generally slowed down – it does not have time to process requests
- some of the applications or services crash
You can check the status of memory, CPU and disk space using the Linux tools ps, top and df.
- Insufficient RAM – when the sum of the memory requirements of all applications, services, other processes and the operating system itself exceeds the amount of RAM you rented (for more information, access the VPS – Insufficient Memory (Out of Memory) article).
- Insufficient processor performance – The processor (or processors) cannot handle requests as they come. Find out which processes are using the system the most, try optimizing them, or shut down some services.
- Insufficient disk space – the df program will check if there is no disk space. Also note that there may be enough space, but you have reached the maximum number of files (i.e. lack of inodes – you can find out whether this is the case with the df -i command). This can often be caused by the “overgrowing” of temporary files, overgrown log files, etc.
- reduce the demands of your server – run fewer services, reduce traffic, etc.
- increase server parameters – choose a more powerful dedicated server or switch to a higher VPS variant
A Problem of the Applications or Services on the Server
The problem is not with the server as a whole, the operating system works without problems, but one specific application or service does not work.
A common problem is that one application crashes – such as a web server or database. As a result, sites running on this server do not work, and users mistakenly consider this to be the overall unavailability of the entire server.
If something like this happens, log in to the server via SSH, find out which service is not running and try to start it again, look at the logs and look for the reason why this happened.
One of the possible causes may again be a lack of system resources – for example, if memory is running low, the operating system will forcibly terminate some services.
The issue can, of course, also be a technical problem on our part.
If all your attempts to connect to your server fail (via SSH and VNC) and a server reset does not solve the problem, contact our customer support, the technicians will check the situation.
An Attack on the Server by an Attacker
Another possibility is that your server has been compromised by an attacker. The goal of such an attack is usually not the misuse of data on the server or their damage, but the use of this server for other attacks (so-called botnet).
If the server behaves abnormally, see the list of running processes. An application could also be attacked, the typical target of attackers are content management systems that have various security holes (typically WordPress).
Infected servers are then misused mainly for DoS attacks or spam. If something like this happens, we are usually informed and we pass this message on to the VPS owner, who must arrange a remedy as soon as possible. In serious cases, we are entitled to shut down the server immediately to minimize any damage.
When looking for the cause of a VPS malfunction, also be sure to check that:
- you didn’t forget to pay for the service’s renewal – in which case you would see the status of this service as ‘suspended’
- there is no planned shutdown of our services – we will either inform you in advance on our website or by e-mail directly to the customer (to the contact address provided with the specific service)