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1500 questions
143
votes
4 answers

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 databases? I have a question regarding capacity planning. Can the…
voretaq7
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143
votes
8 answers

Wildcard SSL certificate for second-level subdomain

I'd like to know if any certificates support a double wildcard like *.*.example.com? I've just been on the phone with my current SSL provider (register.com) and the girl there said they don't offer anything like that and that she didn't think it was…
Rob Long
142
votes
4 answers

Is my password compromised because I forgot to hit Enter after ssh username?

I've just tried logging into a Fedora (release 13 Goddard) server using SSH (PuTTY, Windows). For some reason the Enter after typing my username didn't go through and I typed in my password and hit Enter again. I only realized my mistake when the…
Jonas Heidelberg
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142
votes
6 answers

Why do consoles sometimes hang forever when SSH connection breaks?

I've seen this with so many consoles (on Linux, Mac, ...), and with lots of different machines in many different networks. I can never pinpoint the exact reason, why this happens: All you have to do is log in to a machine via SSH. If the connection…
Chris Lercher
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142
votes
69 answers

The Joel Test for system administrator jobs

Based on “Organizational issues” — sore spots of IT? I think it would be fair to say that system administrators need to determine if a place is worth working at. There is a similar well known test by Joel for programmers. What are the 12 questions…
Nick Kavadias
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141
votes
3 answers

How to remove the "installed manually" flag and revert to "automatically installed" with apt-get?

To compile something, I needed the zlib1g-dev package to be installed so I launched an apt-get install zlib1g-dev. apt-get informed me nicely that the package was already auto-installed because of an other package, and that it understands that I…
Steve Schnepp
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141
votes
2 answers

How can I verify if TLS 1.2 is supported on a remote web server from the RHEL/CentOS shell?

I'm on CentOS 5.9. I'd like to determine from the linux shell if a remote web server specifically supports TLS 1.2 (as opposed to TLS 1.0). Is there an easy way to check for that? I'm not seeing a related option on openssl but perhaps I'm…
Mike B
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141
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7 answers

Where to check log of sendmail?

I can't send out emails, need to look into the logs, but where is the log?
Shore
141
votes
39 answers

What useful things can one add to one's .bashrc?

Is there anything that you can't live without and will make my life SO much easier? Here are some that I use ('diskspace' & 'folders' are particularly handy). # some more ls aliases alias ll='ls -alh' alias la='ls -A' alias l='ls -CFlh' alias…
Gareth
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140
votes
2 answers

What's the difference between include_tasks and import_tasks?

In Ansible 2.4, the include module is deprecated. In its place, it ships with two replacement modules, import_tasks and include_tasks. But they have very similar descriptions: include_tasks: Includes a file with a list of tasks to be executed in…
Ben S
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140
votes
11 answers

Run Oracle SQL script and exit from sqlplus.exe via command prompt

I would like to run an Oracle script through SQL Plus via a Windows command prompt. The script does not contain an "exit" command, but I would still like SQL Plus to exit, returning control to the command prompt on completion of the script. My goal…
JoshL
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140
votes
35 answers

SSH Suddenly returning Invalid format

So a while ago I set up a server on AWS, and used their generated SSH key. I saved the key to Lastpass, and have successfully retrieved it from there before, and got it working. However, after trying that again today, I can't get it to…
Gregor Menih
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140
votes
4 answers

How to handle security updates within Docker containers?

When deploying applications onto servers, there is typically a separation between what the application bundles with itself and what it expects from the platform (operating system and installed packages) to provide. One point of this is that the…
Markus Miller
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140
votes
8 answers

connect() failed (111: Connection refused) while connecting to upstream

I'm experiencing 502 Gateway errors when accessing a PHP file in a directory (http://example.com/dev/index.php). The logs simply says this: 2011/09/30 23:47:54 [error] 31160#0: *35 connect() failed (111: Connection refused) while connecting to…
MacMac
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139
votes
8 answers

In Windows, using the command line, how do you check if a remote port is open?

What is a simple way in Windows to test if traffic gets through to a specific port on a remote machine?
Matt
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