Greatest Hits

671
votes
3answers
582k 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 ...
324
votes
18answers
819k 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.
704
160
votes
7answers
359k 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 id@...
300
votes
23answers
428k 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 ...
408
votes
12answers
507k 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 ...
81
votes
9answers
513k 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 ...
256
votes
8answers
294k views

Can scp copy directories?

Now I can only copy a single tar file,how can I copy directories recursively with scp?
633
215
votes
6answers
387k 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?
99
votes
6answers
690k views

What port does SFTP use?

Does SFTP use port 21 or port 22?
385
346
votes
7answers
279k 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 ...
22
votes
4answers
155k 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 ...
13
votes
1answer
108k 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 C:\Windows\...
64
votes
6answers
497k 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
374k 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 ...
115
votes
10answers
115k 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 ...
1369
votes
28answers
321k 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 ...
444
votes
34answers
214k 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 -...
604
21
votes
3answers
150k 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 ...
167
votes
15answers
450k 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
579k 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 ...
106
votes
2answers
195k 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 Domain, ...
17
votes
13answers
291k 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 ...
149
votes
10answers
411k 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 ...
333
votes
15answers
296k 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 ...
349
403
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
179k 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 ...
137
votes
8answers
135k views

How to force or redirect to SSL in nginx?

I have a signup page on a subdomain like: https://signup.example.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 html/...
59
votes
4answers
263k 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 http://myserver.com/~user=...
72
votes
6answers
315k 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 ...
152
votes
26answers
298k 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 ...
61
votes
3answers
424k 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?
186
votes
5answers
175k 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/. /var/...
134
votes
6answers
180k 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?
118
votes
20answers
114k 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 ...
76
votes
4answers
172k 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
58
votes
6answers
270k 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?
49
votes
6answers
291k 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?
58
votes
12answers
273k 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
259k 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 ...
9
votes
3answers
158k 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?
62
votes
11answers
110k 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 ...
107
votes
11answers
198k 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 ...
62
votes
11answers
160k 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! @ @@@@@...
232
38
votes
4answers
65k 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 ...
77
votes
3answers
163k 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?
94
votes
6answers
197k 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 ...
15
votes
6answers
143k 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
12
votes
3answers
73k 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 ...
216
votes
12answers
74k 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 ...
21
votes
6answers
63k views

how to fix “send-mail: Authorization failed 534 5.7.14 ”

I am trying to create e-mail alert on ssh root login so I had to install ssmtp and mail utility. Then I configured ssmtp.conf file as follows : # Config file for sSMTP sendmail # The person who gets ...