All Questions
40
votes
5answers
5k views
Can you help me with my software licensing issue?
This is a Canonical Question about Licensing.
I have a question regarding software licensing. Can the Server Fault community please help with the following.
How many licenses do I need
Is this ...
240
votes
10answers
39k views
How do I deal with a compromised server?
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 ...
31
votes
2answers
2k views
Can you help me with my capacity planning?
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 ...
200
votes
5answers
33k views
How does IPv4 Subnetting Work?
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 ...
29
votes
3answers
3k views
How do you do Load Testing and Capacity Planning for Web Sites
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 ...
102
votes
5answers
8k views
Everything You Ever Wanted to Know about Mod_Rewrite Rules but Were Afraid to Ask?
How can I become an expert at writing mod_rewrite rules?
What is the fundamental format and structure of mod_rewrite rules?
What form/flavor of regular expressions do I need to have a solid grasp ...
64
votes
2answers
6k views
What are the different widely used RAID levels and when should I consider them?
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?
...
56
votes
5answers
34k views
Multiple SSL domains on the same IP address and same port?
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 ...
40
votes
2answers
4k views
Tips for Securing a LAMP Server
This is a Canonical Question about Securing a LAMP stack
What are the absolute guidelines for securing a LAMP server?
9
votes
6answers
5k views
How to use DNS/Hostnames or Other ways to resolve to a specific IP:Port
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 ...
28
votes
2answers
11k views
What are the best linux permissions to use for my website?
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/.
...
15
votes
2answers
1k views
Why is Linux reporting “free” memory strangely?
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 ...
29
votes
5answers
3k views
Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User?
This is a Canonical Question about Fighting Spam.
Also related: How to stop people from using my domain to send spam?
There are so many techniques and so much to know about fighting SPAM. ...
46
votes
1answer
26k views
What is Active Directory and how does it work?
This is a Canonical Question about Active Directory.
What is Active Directory? What does it do and how does it work?
I find myself explaining some of what I assume is common knowledge about it ...
16
votes
5answers
23k views
How to send emails and avoid them being classified as spam
Sometimes I want to send newsletters to my customers. The problem is, that some of the emails get caught as spam messages. Mostly by Outlook at the client (even in my own Outlook 2007).
Now I want to ...
91
votes
5answers
62k views
What's the best way of handling permissions for apache2's user www-data in /var/www?
Has anyone got a nice solution for handling files in /var/www/ ?
We're running Name Based Virtual Hosts and the apache2 user is 'www-data'
We've got two regular users & root. So when messing ...
0
votes
1answer
698 views
Outgoing mail from linux not being delivered
I can't seem to send mail through my php scripts or through the linux console on my Centos 5.5 LAMP server, when the email is addressed to go to a domain that is hosted by my box.
I think it is ...
8
votes
3answers
9k views
Incredible low disk performance on HP DL385 G7
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 ...
19
votes
5answers
8k views
How to understand the memory usage and load average in linux server
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 ...
48
votes
2answers
51k views
How to Configure Windows Machine to Allow File Sharing with DNS Alias
What process is necessary to configure a Windows environement to allow me to use DNS CNAME to reference servers?
I want to do this so that I can name my servers something like SRV001, but still have ...
36
votes
6answers
3k views
Reinstall after a Root Compromise?
After reading this question on a server compromise, I started to wonder why people continue to seem to believe that they can recover a compromised system using detection/cleanup tools, or by just ...
208
votes
45answers
32k views
Why is Internet access and Wi-Fi always so terrible at large tech conferences? [closed]
Every tech conference I've ever been to, and I've been to a lot, has had absolutely abysmal Wi-Fi and Internet access.
Sometimes it's the DHCP server running out of addresses. Sometimes the backhaul ...
84
votes
4answers
20k views
LVM dangers and caveats
I have recently started using LVM on some servers for hard drives larger than 1 TB. They're useful, expandable and quite easy to install. However, I could not find any data about the dangers and ...
48
votes
14answers
6k views
Hundreds of failed ssh logins
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 ...
29
votes
3answers
25k views
Meaning of the buffers/cache line in the output of free
Why does my server show
total used free shared buffers cached
Mem: 12286456 11715372 571084 0 81912 6545228
-/+ buffers/cache: 5088232 7198224
...
19
votes
1answer
1k views
Why is my crontab not working, and how can I troubleshoot it?
This is a Canonical Question about using crontab.
The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below. This addresses the cron system with the ...
4
votes
2answers
2k views
How to reset or recover admin account password for MySql?
I have a MySql database that I "inherited" and I was not given the admin credentials. I do however have access to the box that it runs on. Is there a way to either recover the admin credentials or ...
367
votes
5answers
118k views
Anyone else experiencing high rates of Linux server crashes during a leap second day?
*NOTE: if your server still has issues due to confused kernels, and you can't reboot - the simplest solution proposed with gnu date installed on your system is: date -s now. This will reset the ...
73
votes
15answers
58k views
Why is DNS failover not recommended?
From reading, it seems like DNS failover is not recommended just because DNS wasn't designed for it. But if you have two webservers on different subnets hosting redundant content, what other methods ...
89
votes
6answers
4k views
What’s the point in having “www” in a URL?
Other than for historical reasons, is there is reason to have “www” in a URL.
Should I do a permanent redirect from www.xyz.com to xyz.com or xyz.com to www.xyz.com? Which one would you suggest and ...
16
votes
3answers
4k views
Linux - real-world hardware RAID controller tuning (scsi and cciss)
Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS.
I'm looking for real-world tunables to help optimize performance for ...
9
votes
1answer
746 views
How do you do Load Testing and Capacity Planning for Databases
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 ...
20
votes
3answers
3k views
1
vote
3answers
5k views
FTP and Apache permission issues
Im having issues as to which user should own my www directory - ftp or apache?
When set to the ftp user, the user can add, remoe and easily modify files but php file system actions generate permission ...
77
votes
12answers
9k views
Using revision control for server configuration files?
In an environment with multiple system administrators, I see a few advantages to adding the server config files into a revision control system. Most notable are the ability to track changes, who made ...
37
votes
15answers
3k views
What's your favorite ticketing system? [closed]
I'm in the market for a ticketing system and I'm curious what everyone else is using. I'd like to welcome everyone to post their favorite ticketing system and the reason they like it so much.
My ...
45
votes
5answers
19k views
Setting the hostname: FQDN or short name?
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 ...
38
votes
20answers
10k views
rm on a directory with millions of files
Background: physical server, about two years old, 7200-RPM SATA drives connected to a 3Ware RAID card, ext3 FS mounted noatime and data=ordered, not under crazy load, kernel 2.6.18-92.1.22.el5, uptime ...
15
votes
4answers
1k views
Best Practices for preventing you from looking like a spammer
I'd like to feel more confident setting up mail for my clients with regards to false positives. Here's what I know:
SPF records are good, but not every spam filter service/software (SFSS) uses ...
46
votes
8answers
3k views
How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?
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 ...
9
votes
5answers
10k views
Cygwin SSHd Autoblock Failed Logins
I'm running Cygwin with an SSH deamon on a Windows Server 2008 machine. I was looking at the Event Viewer and noticed as much as 5 to 6 failed login attempts per second (brute force) for the last week ...
65
votes
6answers
7k views
Why is business-class storage so expensive?
This is a Canonical Question about the Cost of Enterprise Storage.
See also the following question:
What's the best way to explain storage issues to developers and other users
...
57
votes
9answers
12k views
How to stop people from using my domain to send spam?
This is a Canonical Question about Fighting Spam. Other relevant questions include
* Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User?
I receive Mailer Daemon ...
10
votes
4answers
10k views
How do I tell if my Windows server is swapping?
I'm using Process Explorer to monitor my windows server while it reconstructs some data. It's primarily a CPU intensive process, but I want to make sure it's not swapping. How can I tell if it is ...
14
votes
2answers
826 views
Find out which process is changing a file
I'm trying to find a reliable way of finding which process on my machine is changing a configuration file (/etc/hosts to be specific).
I know I can use lsof /etc/hosts to find out what processes ...
12
votes
17answers
6k views
Who is your favorite VPS Provider? [closed]
Who is your favorite virtual hosting provider? I'm looking for your thoughts on SliceHost, Dreamhost VPS, Linode, 1and1 VPS, etc and why you like the particular provider you named.
Thanks!
128
votes
11answers
38k views
Can I nohup/screen an already-started process?
I'm doing some test-runs of long-running data migration scripts, over SSH. Let's say I start running a script around 4 PM; now, 6 PM rolls around, and I'm cursing myself for not doing this all in ...
122
votes
2answers
6k views
Why is “chmod -R 777 /” destructive?
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 ...
9
votes
1answer
3k views
Hosting a ZFS server as a virtual guest
I'm still new to ZFS. I've been using Nexenta but I'm thinking of switching to OpenIndiana or Solaris 11 Express. Right now, I'm at a point of considering virtualizing the ZFS server as a guest within ...
61
votes
14answers
3k views
What's wrong with always being root?
I have a feeling this is a stupid question, but this is something I've wondered for awhile.
I have a VPS and this is my first big linux venture. I am the only person who has access to it. My question ...
