Greatest Hits

647
votes
3answers
564k views

What is a Pem file and how does it differ from other OpenSSL Generated Key File Formats?

I am responsible for maintaining two Debian servers. Every time I have to do anything with security certificates, I Google for tutorials and beat away until it finally works. However, in my searches ...
315
votes
18answers
789k views

Ping a Specific Port

Just a quick sanity check here. Can you ping a specific port of a machine, and if so, can you provide an example? I'm looking for something like ping ip address portNum.
681
148
votes
7answers
345k views

How to automate SSH login with password?

How to automate SSH login with password? I'm configuring my test VM, so heavy security is not considered. SSH chosen for acceptable security with minimal configuration. ex) echo password | ssh ...
298
votes
22answers
415k views

How do I tell Git for Windows where to find my private RSA key?

My GIT setup runs fine in Linux, but when I try to set things up under Windows (using Git for Windows and TortoiseGit), I don't know where to put my private ssh key (or, better still, how to tell ssh ...
81
votes
9answers
501k views

Command line to list users in a Windows Active Directory group?

Is there a command line way to list all the users in a particular Active Directory group? I can see who is in the group by going to Manage Computer --> Local User / Groups --> Groups and double ...
395
votes
12answers
490k views

How to determine if a bash variable is empty?

What is the best way to determine if a variable in bash is empty ("")? I have heard that it is recommended that I do if [ "x$variable" = "x" ] Is that the correct way? (there must be something more ...
252
votes
8answers
284k views

Can scp copy directories?

Now I can only copy a single tar file,how can I copy directories recursively with scp?
617
210
votes
6answers
374k views

What's the default superuser username/password for postgres after a new install?

I have just installed postgres 8.4 on Ubuntu 9.10 and it has never asked me to create a superuser. Is there a default superuser and its password? If not, how do I create a new one?
97
votes
6answers
679k views

What port does SFTP use?

Does SFTP use port 21 or port 22?
380
22
votes
4answers
151k views

Outlook 2013: how to reset to “first run” status?

TL;DR Is there a way via script, powershell, reg delete, via telekinesis, whatever to reset Outlook 2013 as if no profiles ever existed and it was running for the first time ever? Still working ...
335
votes
7answers
272k views

In Nginx, how can I rewrite all http requests to https while maintaining sub-domain?

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 ...
13
votes
1answer
107k views

What is a S-X-X-XX-XXXXXXXXXX-XXXXXXXXXX-XXXXXXXXX-XXXX called in Windows security?

I copied two trees, a source and a destination, that I copied with robocopy like this: robocopy /MIR C:\Windows\System32\tasks\ C:\temp\robocopyTasks\out\ robocopy /E /Copy:S /IS /IT ...
64
votes
6answers
495k views

How to determine the hostname from an IP address in a Windows network?

My LAN has 50 Windows hosts. At the Windows command line I try ping to get the IP address of a running Windows machine. The question is how to get hostname of a specific IP address in the same ...
45
votes
8answers
369k views

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 ...
112
votes
10answers
112k views

Monday morning mistake: sudo rm -rf --no-preserve-root /

Please note: The answers and comments to this question contains content from another, similar question that has received a lot of attention from outside media but turned out to be hoax question in ...
1360
votes
28answers
320k views

Our security auditor is an idiot. How do I give him the information he wants?

A security auditor for our servers has demanded the following within two weeks: A list of current usernames and plain-text passwords for all user accounts on all servers A list of all password ...
431
votes
34answers
206k views

How can I sort du -h output by size

I need to get a list of human readable du output. However, du does not have a "sort by size" option, and piping to sort doesn't work with the human readable flag. For example, running: du | sort ...
584
21
votes
3answers
139k views

Registry key / GPO to disable and block Windows 10 upgrade?

One of our remote Windows 7 Professional users just reported that he received an Upgrade Reservation Offer for Windows 10. It appears the Get Windows 10 "App" running in his system tray is legit. So ...
163
votes
15answers
441k views

Why do I get “Permission denied (publickey)” when trying to SSH from local Ubuntu to a Amazon EC2 server?

I have an instance of an application running in the cloud on Amazon EC2 instance, and I need to connect it from my local Ubuntu. It works fine on one of local ubuntu and also laptop. I got message ...
21
votes
8answers
577k views

How to format as FAT32 from Windows 7/Vista

What is the best way to format a USB drive with FAT32 (for Mac compatibility) from within Windows 7/Vista? I ask because the Disk Management only lets you pick exFAT (because the disk is over 32GB I ...
105
votes
2answers
192k views

What is Active Directory Domain Services and how does it work?

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 ...
17
votes
13answers
288k views

Error 0x80070570: How to delete corrupted and unreadable file?

On my system partition I have a folder which cannot be deleted. This folder has been created by restoring files from an Acronis TrueImage backup. The error message says: Error 0x80070570: The ...
145
votes
10answers
401k views

What's the command-line utility in Windows to do a reverse DNS look-up?

Is there a built-in command line tool that will do reverse DNS look-ups in Windows? I.e., something like <toolname> w.x.y.z => mycomputername I've tried: nslookup: seems to be forward ...
324
votes
15answers
288k views

How do you find what process is holding a file open in Windows?

One thing that annoys me no end about Windows is the old sharing violation error. Often you can't identify what's holding it open. Usually it's just an editor or explorer just pointing to a relevant ...
339
402
votes
7answers
65k views

Something is burning in the server room; how can I quickly identify what it is?

The other day, we notice a terrible burning smell coming out of the server room. Long story short, it ended up being one of the battery modules that was burning up in the UPS unit, but it took a good ...
416
69
votes
9answers
178k views

Can't seem to disable Java Automatic Update

I'm just tweaking out my new Windows 7 laptop and wanted to disable the automatic Java updating (and thus kill the silly jusched.exe background process), but I can't seem to get it to actually turn it ...
133
votes
8answers
131k views

How to force or redirect to SSL in nginx?

I have a signup page on a subdomain like: https://signup.mysite.com It should only be accessible via HTTPS but I'm worried people might somehow stumble upon it via HTTP and get a 404. My ...
58
votes
4answers
251k views

Can you pass user/pass for HTTP Basic Authentication in URL parameters?

I believe this is not possible, but someone I know insisted that it works. I don't even know what parameters to try, and I haven't found this documented anywhere. I tried ...
70
votes
6answers
307k views

How can I figure out my LDAP connection string?

We're on a corporate network thats running active directory and we'd like to test out some LDAP stuff (active directory membership provider, actually) and so far, none of us can figure out what our ...
149
votes
26answers
293k views

Using DD for disk cloning

There's been a number of questions regarding disk cloning tools and dd has been suggested at least once. I've already considered using dd myself, mainly because ease of use, and that it's readily ...
60
votes
3answers
416k views

How to check if a port is blocked on a Windows machine?

On the Windows platform, what native options to I have to check if a port (3306, for example) on my local machine (as in localhost), is being blocked?
118
votes
20answers
113k views

How do you install Node.JS on CentOS?

I've found numerous installation instructions for Node.js but they all seem so complicated -- I'm not a super sys admin but I can get around. I have yum on the system, but I didn't find any node.js ...
179
votes
5answers
168k views

What permissions should my website files/folders have on a Linux webserver?

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/. ...
131
votes
6answers
175k views

How can I find out what AD groups I'm a member of?

I'm running a Windows XP desktop in a corporate environment. How can I find out what AD groups I belong to?
76
votes
4answers
170k views

How to make Windows 7 USB flash install media from Linux?

I have: ISO image of Windows 7 install media 4 GB USB flash drive no DVD drive Linux installed
48
votes
6answers
286k views

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?
54
votes
6answers
260k views

Check if port is open or closed on a Linux server?

How can I check if a port is listening on a Linux server?
57
votes
12answers
269k views

How to start/stop iptables on Ubuntu?

How can I start/stop the iptables service on Ubuntu? I have tried service iptables stop but it is giving "unrecognized service". Why is it doing so? Is there any other method?
24
votes
10answers
254k views

How do I get this SQL Server ODBC Connection working?

Note: I've obviously changed the server names and IPs to fictitious ones. Here's what's going on. I've got a server, which I'm calling MYSERVER, running Microsoft SQL Server Express 2005. Right on ...
8
votes
3answers
151k views

How to set the Internet Explorer Home Page via GPO?

I need to set the default home page for the entire domain via GPO. Where is the IE Home Page Policy located?
61
votes
11answers
108k views

IIS 7.5 (Windows 7) - HTTP Error 401.3 - Unauthorized

I'm trying to test my ASP.Net website on localhost and I'm getting this error: HTTP Error 401.3 - Unauthorized You do not have permission to view this directory or page because of the access control ...
104
votes
11answers
195k views

Run a .bat file in a scheduled task without a window

I have a scheduled task that starts a batch script that runs robocopy every hour. Every time it runs a window pops up on the desktop with robocopy's output, which I don't really want to see. I ...
36
votes
4answers
62k views

EPEL Repo for CentOS 6 causing error

I've got a VM running CentOS 6 (64bit) and I'm attempting to add the EPEL repo like usual to install various packages as I do quite regularly. Today, I'm experiencing some strange errors yet I'm ...
61
votes
9answers
154k views

“Add correct host key in known_hosts” / multiple ssh host keys per hostname?

Trying to ssh into a computer I control, I'm getting the familiar message: @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ ...
223
93
votes
6answers
192k views

What version of RHEL am I using?

From the shell and without root privileges, how can I determine what Red Hat Enterprise Linux version I'm running? Ideally, I'd like to get both the major and minor release version, for example RHEL ...
12
votes
3answers
72k views

How do I cleanly remove apache2 server on ubuntu server and then reinstall?

I am having some wierd issues with Apache2 server on my ubuntu server. I believe some configuration files may have been tampered with. What is the easiest way to remove apache2 completely from my ...
215
votes
12answers
73k views

Is it bad to redirect http to https?

I just installed an SSL Certificate on my server. It then set up a redirect for all traffic on my domain on Port 80 to redirect it to Port 443. In other words, all my http://example.com traffic is ...
75
votes
3answers
159k views

How to sleep in a batch file?

How to pause execution for a while in a Windows batch file between a command and the next one?
15
votes
6answers
140k views

Get IP addresses and Computer Names in the Same Network

What is the command that can be used to get the IP address and the names of the computers that are located in the same network? I am running Windows
49
votes
5answers
220k views

What's the difference between Windows Server 2008, 2008 SP2 and 2008 R2?

What are the major differences between Windows Server 2008, 2008 SP2 and 2008 R2? Are the code bases for these OSes different? If I'm developing applications for any one of these three, should I be ...