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This is a Canonical Question about Server Security - Responding to Breach Events (Hacking) See Also: Tips for Securing a LAMP Server Reinstall after a Root Compromise? Canonical ...

This is a Canonical Question about Licensing. Questions on licensing are off-topic on Server Fault. If your question has been closed as a duplicate of this question, then this is because we want to ...

This is a canonical question about capacity planning Related: How do you do load testing and capacity planning for web sites? How do you do load testing and capacity planning for databases? I have a ...

This is a Canonical Question about Apache's mod_rewrite. Changing a request URL or redirecting users to a different URL than the one they originally requested is done using mod_rewrite. This includes ...

This is a Canonical Question about using cron & crontab. You have been directed here because the community is fairly sure that the answer to your question can be found below. If your question is ...

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it by ...

This is a canonical question about capacity planning for web sites. Related: Can you help me with my capacity planning? How do you do load testing and capacity planning for databases? What are some ...

This is a canonical question about how to handle email sent from your server being misclassified as spam. For additional information you may find these similar questions helpful: Best ...

This is a Canonical Question about DoS and DDoS mitigation. I found a massive traffic spike on a website that I host today; I am getting thousands of connections a second and I see I'm using all ...

This is a Canonical Question about Connection Refused We see a lot of questions to the effect When I try to connect to a system I get a message Connection refused Why is this ?

For a more comprehensive list of monitoring tools and their features, check out this Wikipedia page. As the question states, what are the most commonly used tools used for this task and what are ...

This is a Canonical Question about RAID levels. What are: the RAID levels typically used (including the RAID-Z family)? deployments are they commonly found in? benefits and pitfalls of each?

This is a canonical question about setting up SPF records. I have an office with many computers that share a single external ip (I'm unsure if the address is static or dynamic). Each computer ...

This is a Canonical Question about Fighting Spam. Also related: How to stop people from using my domain to send spam? What are SPF records, and how do I configure them? There are so ...

This is a Canonical Question about File Permissions on a Linux web server. I have a Linux web server running Apache2 that hosts several websites. Each website has its own folder in /var/www/. /var/...

This is a Canonical Question about Active Directory domain naming. After experimenting with Windows domains and domain controllers in a virtual environment, I've realized that having an active ...

This is a Canonical Question about Hairpin NAT (Loopback NAT). The generic form of this question is: We have a network with clients, a server, and a NAT Router. There is port forwarding on the ...

This is a Canonical Question about DNS glue records. What exactly (but briefly) is a DNS glue record? Why are they needed and how do they work?

This is a canonical question about how Unix operating systems report memory usage. Similar Questions: Server refuses to use swap partition Memory Usage in LINUX I have production ...

This is a Canonical Question about DNS/Hostnames resolution to IPs/Ports Example 1 I'm running a web server on port 80 and another on port 87. I would like to use DNS so that www.example.com goes to ...

This is a Canonical Question about CNAMEs at the apices (or roots) of zones It's relatively common knowledge that CNAME records at the apex of a domain are a taboo practice. Example: example.com. IN ...

This is a Canonical Question about Hosting multiple SSL websites on the same IP. I was under the impression that each SSL Certificate required it's own unique IP Address/Port combination. But the ...

This is a canonical question about avoiding outgoing mail being classified as spam. Also related: Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User? What ...

This is a canonical question about the use of a *AMPP's stack. I recently had a talk with some experienced people and they suggested to me not to use a WAMP stack, and instead install apache, mysql ...

This is a Canonical Question about Active Directory Domain Services (AD DS). What is Active Directory? What does it do and how does it work? How is Active Directory organized: Forest, Child Domain, ...

I have a SCSI disk in a server (hardware Raid 1), 32G, ext3 filesytem. df tells me that the disk is 100% full. If I delete 1G this is correctly shown. However, if I run a du -h -x / then du tells me ...

This is a Canonical Question about Securing a LAMP stack What are the absolute guidelines for securing a LAMP server?

I've been working with OpenSolaris and ZFS for 6 months, primarily on a Sun Fire x4540 and standard Dell and HP hardware. One downside to standard Perc and HP Smart Array controllers is that they do ...

This is a Canonical Question about File Permission and Why 777 is "destructive". I'm not asking how to fix this problem, as there are a ton of references of that already on Server Fault (reinstall OS)...

This is a Canonical Question about whether to outsource DNS resolution for ones own domains I currently have my ISP providing DNS for my domain, but they impose limitations on adding records. ...

I have a a large number of sleeping processes, about 600, the majority of which are Apache processes. Should I kill all these sleeping processes, or will that make Apache fail completely? Why are ...

This is a Canonical Question about System Administration Careers When I start my job as System Administrator, what basics skills should I know/learn? Are there any key differences for Network, ...

I've noticed that the "preferred" method of setting the system hostname is fundamentally different between Red Hat/CentOS and Debian/Ubuntu systems. CentOS documentation and the RHEL deployment guide ...

This is a canonical question about capacity planning for databases. Related: Can you help me with my capacity planning? How do you do load testing and capacity planning for web sites? I'm looking to ...

This is a Canonical Question about DNS geo-redundancy. It's extremely common knowledge that geo-redundant DNS servers located at separate physical locations are highly desirable when providing ...

I am using a linux server which has 128GB of memory and 24 cores. I use top to see how much it is used. Its output is pasted at the end of the post. Here are two questions: (1) I see that each of the ...

Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved our ...

I was wondering if anyone had any specific experience using Intel DC3700 SSDs (or similar) in the HP (DL380p) Gen8 servers? I'm upgrading a set of database servers that use direct-attached storage. ...

Has anyone got a nice solution for handling files in /var/www? We're running Name Based Virtual Hosts and the Apache 2 user is www-data. We've got two regular users & root. So when messing with ...

I know that the ip tool lets you bind multiple addresses to an interface (eg, http://www.linuxplanet.com/linuxplanet/tutorials/6553/1/). Right now, though, I'm trying to build something on top of IPv6,...

I've grown quite fond of HTTP reverse proxies in our development environment and found the DNS based virtual host reverse proxy quite useful. Having only one port (and the standard one) open on the ...

SSD drives have been around for several years now. But the issue of reliability still comes up. I guess this is a follow up from this question posted 4 years ago, and last updated in 2011. It's now ...

As a test of the Opteron processor family, I bought a HP DL385 G7 6128 with HP Smart Array P410i Controller - no memory. The machine has 20GB ram 2x146GB 15k rpm SAS + 2x250GB SATA2, both in Raid 1 ...

I want to rewrite all http requests on my web server to be https requests, I started with the following: server { listen 80; location / { rewrite ^(.*) https://mysite.com$1 ...

Why does my server show total used free shared buffers cached Mem: 12286456 11715372 571084 0 81912 6545228 -/+ buffers/cache: 5088232 7198224 Swap:...

An SD (SDHC) card installed in an HP ProLiant DL380p Gen8 server running VMware ESXi just failed :( I encountered some ominous looking messages on the vCenter console and in the HP ProLiant ILO event ...

This is a Canonical Question about understanding and remediating the Heartbleed security issue. What exactly is CVE-2014-0160 AKA "Heartbleed"? What is the cause, what OSs and versions of OpenSSL are ...

I have a fileserver where df reports 94% of / full. But according to du, much less is used: # df -h / Filesystem Size Used Avail Use% Mounted on /dev/sda3 270G 240G 17G 94%...

It's the following part of a virtual host config that I need further clarification on: <VirtualHost *:80> # Admin email, Server Name (domain name), and any aliases ServerAdmin example@...

Every night I get hundreds, sometimes thousands, of failed ssh logins on my RedHat 4 server. For firewall reasons from remote sites, I need to run on the standard port. Is there anything I should be ...