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1500 questions
60
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5 answers
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 running processes occupies a very small…
Tim
- 1,517
60
votes
10 answers
How to determine AWS security group dependencies?
Amazon EC2 won't let me delete a security group, complaining that the group still has dependencies. How Can I find what those dependencies are?
aws ec2 describe-security-groups doesn't say.
user14645
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- 2
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60
votes
7 answers
adding password to .ssh/config
I'm using ubuntu 12.04. I'm using ssh for connecting to many servers daily, so I put their parameters in .ssh/config file; like this :
Host server1
User tux
Port 2202
HostName xxx.x.xx.x
I know we should use key-pair ensure security, however…
Ajo Augustine
- 1,262
60
votes
10 answers
how to use xauth to run graphical application via other user on linux
My regular user account is, let's say, user1. I created separate user2 for some x application that i would like to run while being logged into x as user1 but in a way that will prevent it from read/write access to user1 data. I thought that i could…
Phil
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60
votes
4 answers
Multiple EC2 security groups - permissive or restrictive?
What happens when I assign multiple security groups to an instance? Is it permissive in the sense that the traffic is allowed in if any one of the security groups allows it. OR is it restrictive in the sense that every security group must allow…
Suraj
- 855
60
votes
18 answers
Favorite rsync tips and tricks
The more I use rsync the more I realise that it's a swiss army knife of file transfer. There are so many options. I recently found out that you can go --remove-source-files and it'll delete a file from the source when it's been copied, which makes…
Amandasaurus
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- 69
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- 263
60
votes
8 answers
What does "TTL expired in transit" mean on a ping attempt?
We get the message “TTL expired in transit” when we try to ping to a server in a different network segment. When we run tracert, 4 ip addresses repeat themselves indefinitely:
14 60 ms 59 ms 60 ms xxx.xxx.xxx.2
15 83 ms 81 ms 82…
Leonardo
- 705
60
votes
6 answers
Ending company IT Admin relationship
We have been using a company to administer our (small office) IT infrastructure. We don't have complete records of what has been done or hasn't been done and don't know what we need to ask for in order to pick this up ourselves. Is there a good…
albiglan
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votes
7 answers
How do I know I'm running inside a linux "screen" or not?
The "screen" refers to a program mentioned in How to reconnect to a disconnected ssh session . That is a good facility.
But there is a question I'd really like to know. How do I know whether I'm running inside a "screen"? The difference is:
If…
Jimm Chen
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60
votes
2 answers
What are SPF records, and how do I configure them?
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 connects to our mail server via IMAP using outlook.…
vulgarbulgar
- 759
60
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
- 986
60
votes
4 answers
nginx without server_name and using only static ip address?
this is my first web app deployment and am running into all sorts of issues.
I am currently going for a nginx + gunicorn implementation for the Django app, but mostly this question relates to nginx configurations. For some context - nginx would…
bash-
- 847
60
votes
3 answers
Do Apache config files support block commenting?
You can use # to comment out individual lines.
Is there a syntax for commenting out entire blocks?
I've tired surrounding the block (specifically a block) with ... , but that didn't work.
ripper234
- 6,040
60
votes
3 answers
Soft limit vs Hard limit?
Can anyone explain in layman's terms what the difference between soft and hard limit is?
Should I set my soft and hard limit to be the same? Or should soft be significantly lower? Does the system benefit either way?
kidcapital
- 857
60
votes
5 answers
iptables port redirect not working for localhost
I want to redirect all traffic from port 443 to the internal port 8080. I'm using this config for iptables:
iptables -t nat -I PREROUTING --source 0/0 --destination 0/0 -p tcp \
--dport 443 -j REDIRECT --to-ports 8080
This works for all…
Chris
- 601