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1500 questions
56
votes
4 answers
DIMMs: Single vs. Double vs. Quad Rank
What difference does the 'Rank' of DIMMs make to server memory? For example, when looking at server configurations I see the following being offered for the same server:
2GB (1x2GB) Single Rank PC3-10600 CL9 ECC DDR3-1333 VLP RDIMM
2GB (1x2GB) Dual…
MikeyB
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56
votes
3 answers
How to fix 'logjam' vulnerability in Apache (httpd)
Recently, a new vulnerability in Diffie-Hellman, informally referred to as 'logjam' has been published, for which this page has been put together suggesting how to counter the vulnerability:
We have three recommendations for correctly deploying…
Christophe De Troyer
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56
votes
1 answer
how to access host variable of a different host with Ansible?
Let's say I have a host that collects some data and it's in a group [collectors]. I also have hosts in-group [reporters].
So, I want to set a variable on reporters from groups['collectors'][0] IP address. But the playbook for setting up reporters…
hryamzik
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56
votes
6 answers
Why do we still use power supplies on datacenter servers?
Computers mainly need three voltages to work : +12V, +5V and +3,3V, all of them are DC.
Why can't we just have a few (for redundancy) big power supply providing these three voltages to the entire datacenter, and servers directly using it ?
That…
user186340
56
votes
3 answers
Configure Nginx as reverse proxy with upstream SSL
I try to configure an Nginx server as a reverse proxy so the https requests it receives from clients are forwarded to the upstream server via https as well.
Here's the configuration that I use:
http {
# enable reverse proxy
proxy_redirect …
Alex Flo
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56
votes
12 answers
How do I make Linux recognize a new SATA /dev/sda drive I hot swapped in without rebooting?
Hot swapping out a failed SATA /dev/sda drive worked fine, but when I went to swap in a new drive, it wasn't recognized:
[root@fs-2 ~]# tail -18 /var/log/messages
May 5 16:54:35 fs-2 kernel: ata1: exception Emask 0x10 SAct 0x0 SErr 0x50000 action…
Philip Durbin
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56
votes
5 answers
Which to install: Apache Worker or Prefork? What are the (dis-)advantages of each?
Based on the descriptions for both the Prefork and Worker MPM, it seems the prefork type is somewhat outdated, but I can't really find a proper comparison of the two types.
What i'd like to know:
What are the differences between the two…
Aron Rotteveel
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56
votes
6 answers
How do I force Linux to reacquire a new IP address from the DHCP server?
The environment is Debian, although the answer will apply to all distributions.
GeneQ
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56
votes
4 answers
Assessing equipment damage following a lightning strike - Should I have planned more?
One of my client's sites received a direct lightning hit last week (coincidentally on Friday the 13th!).
I was remote to the site, but working with someone onsite, I discovered a strange pattern of damage. Both internet links were down, most servers…
ewwhite
- 197,159
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56
votes
4 answers
Why is my rsync so slow?
My Laptop and my workstation are both connected to a Gigabit Switch. Both are running Linux. But when I copy files with rsync, it performs badly.
I get about 22 MB/s. Shouldn't I theoretically get about 125 MB/s? What is the limiting factor…
iblue
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56
votes
2 answers
Mysterious visitor to hidden PHP page
On my website, I have a "hidden" page that displays a list of the most recent visitors. There exist no links at all to this single PHP page, and, theoretically, only I know of its existence. I check it many times per day to see what new hits I…
Bill
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56
votes
4 answers
How to specify multiple included domains in SPF record?
Our business email is hosted on Google apps. In addition, our web server may also send email. Currently our SPF record in DNS looks like this:
domain.com. IN TXT "v=spf1 a include:_spf.google.com -all"
This is all fine, however now we've…
Aleks G
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56
votes
14 answers
Is UPS worthwhile for non-production equipment?
Over the years, I've had to throw away a quite a few bits of computing equipment (and the like):
Several ADSL routers with odd symptoms (losing wireless connections, losing wired connections, DHCP failures, DNS symptoms etc)
Two PVRs spontaneously…
Jon Skeet
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56
votes
11 answers
Is there an equivalent to ssh-copy-id for Windows?
Is there any equivalent or port of ssh-copy-id available for Windows? That is, is there an easy way to transfer SSH keys from a local machine to a remote server under Windows?
In case it helps, I'm using Pageant and Kitty (a Putty alternative)…
Matt V.
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56
votes
2 answers
Difference between Xen PV, Xen KVM and HVM?
I know that Xen is usually better than OpenVZ as the provider cannot oversell in Xen.
However, what is the difference between Xen PV, Xen KVM and HVM (I was going through this provider's specs? Which one is better for what purposes and why?…
JP19