Greatest Hits

29
votes
6answers
42k views

Send ctrl-alt-del to nested RDP session

Is there a way to send the ctrl-alt-del command to an RDP session (W2K8 R2) inside another RDP session (W2K8 R2) without the fist session catching it? ctrl+alt+end and ctrl+alt+shift+end do not reach ...
5
votes
3answers
86k views

Email bounce back 550 5.1.1 recipient rejected

A client recently switched to Exchange Server / Outlook for their email. Since then emails from my company to any email address at their company bounce back from the System Administrator with this ...
19
votes
10answers
101k views

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: ...
13
votes
5answers
87k views

How do I configure proxy settings for LOCAL SYSTEM?

If I edit Proxy Settings through the Control Panel, the settings are stored in HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\ProxyEnable and ...\ProxyServer. These ...
67
votes
11answers
71k views

apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName

I keep getting this warning when I (re)start Apache. * Restarting web server apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ...
16
votes
10answers
144k views

Best way to find the computer a user last logged on from?

I am hoping that somewhere in Active Directory the "last logged on from [computer]" is written/stored, or there is a log I can parse out? The purpose of wanting to know the last PC logged on from is ...
9
votes
6answers
69k views

SQL - an error occurred during the pre-login handshake

Until yesterday evening, I was able to connect to my server from my local machine. Now, I get the following error: A connection was successfully established with the server, but then an error ...
6
votes
8answers
113k views

Enforcing lock screen after idle time via GPO

I run a network of computers and I would like enforce a GPO which locks the screen after a predefined idle time. I can't find this setting, I can only find a screen saver idle time setting, how can I ...
35
votes
2answers
99k views

How do I view the details of a digital certificate .cer file?

I am using Windows and have been given a .cer file. How can I view the details of it?
29
votes
6answers
83k views

High load average, low CPU usage - why?

We're seeing huge performance problems on a web application and we're trying to find the bottleneck. I am not a sysadmin so there is some stuff I don't quite get. Some basic investigation shows the ...
13
votes
2answers
25k views

What is ADFS (Active Directory Federation Services)?

So I've been told that our PHP application may need to support authentication using ADFS. For a non-Microsoft person, what is ADFS? How does it differ to things like LDAP? How does it work? What ...
22
votes
7answers
47k views

df says disk is full, but it is not

On a virtualized server running Ubuntu 10.04, df reports the following: # df -h Filesystem Size Used Avail Use% Mounted on /dev/sda1 7.4G 7.0G 0 100% / none ...
15
votes
4answers
74k views

Best Practice: vCPUs per physical core

I am trying to find some documentation or best practice guides for virtualization with respect to provisioning vCPUs per physical core (of a CPU). If it matters, I am looking at vmWare for the ...
31
votes
6answers
71k views

How can I list my open ports on Debian?

What is the command to display a list of open ports on a Debian server? I tried netstat -a | egrep 'Proto|LISTEN' but I would like something more specific that actually lists the port number.
30
votes
6answers
80k views

How to remove strict RSA key checking in SSH and what's the problem here?

I have a Linux server that whenever I connect it shows me the message that changed the SSH host key: $ ssh root@host1 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: ...
39
votes
3answers
79k views

How do I extract login history?

I need to know the login history for specific user (i.e. login and logout time), How do I extract this history for a specific date range in Linux ?
124
votes
12answers
128k views

How to set up Nginx as a caching reverse proxy?

I heard recently that Nginx has added caching to its reverse proxy feature. I looked around but couldn't find much info about it. I want to set up Nginx as a caching reverse proxy in front of Apache/...
20
votes
13answers
72k views

How to get a list of drive letters on a system through a windows shell (bat, cmd)?

How do I get a list of drive letters and their associated labels on a windows system through a bat file?
189
votes
9answers
29k views

Heartbleed: What is it and what are options to mitigate it?

This is a Canonical Question about understanding and remediating the Heartbleed security issue. What exactly is CVE-2014-0160 AKA "Heartbleed"? What is the cause, what OSs and versions of OpenSSL ...
18
votes
7answers
62k views

ssh tunnel refusing connections with “channel 2: open failed”

All of a sudden (read: without changing any parameters) my netbsd virtualmachine started acting oddly. The symptoms concern ssh tunneling. From my laptop I launch: $ ssh -L 7000:localhost:7000 user@...
24
votes
3answers
82k views

How to stream live video from a linux server?

Here is what I want to do. Looked around but didnt find any straight answer. I have a Linux box running websites using Ubuntu/MySQL/Apache. I have my own static IP as well, i.e. not using web hosting. ...
45
votes
5answers
106k views

How do I grant start/stop/restart permissions on a service to an arbitrary user or group on a non-domain-member server?

We have a suite of Windows Services running on our servers which perform a bunch of automated tasks independently of one another, with the exception of one service which looks after the other services....
23
votes
7answers
100k views

What is the value of JAVA_HOME for CentOS?

I have install java through yum on CentOS, however another java programme needs to know what the JAVA_HOME environmental variable is. I know all about setting environmental variables, but what do I ...
8
votes
3answers
53k views

Difference between 2Rx4 vs 2Rx8 RAM

My IT provider is convincing me there is no difference between a 2Rx4 and a 2Rx8 RAM. A little digging around informed me that x4 means 4 bits on a chip vs x8 means 8 bits. Which is good, but what ...
105
33
votes
6answers
27k views

Software vs hardware RAID performance and cache usage

I've been reading a lot on RAID controllers/setups and one thing that comes up a lot is how hardware controllers without cache offer the same performance as software RAID. Is this really the case? I ...
67
votes
4answers
97k views

How can I see Time-To-Live (TTL) for a DNS record?

I would like to see the Time-To-Live (TTL) value for a CNAME record. I have access to dig (on Apple Mac OS X), which gives me an answer like this: % dig host.example.gov <*SNIP*> ;; ANSWER ...
4
votes
4answers
36k views

How to export a detailed list of Active Directory users' “Member of” tab?

I am currently in the process of restructuring the Active Directory user list of the company I'm working for, and the person who did it did an awful job, and is of course, not working here anymore. ...
41
votes
3answers
43k views

How do I auto-start docker containers at system boot?

What is a good way to automatically start docker containers when the system boots up? Is there a preferred way to do this on Ubuntu 14.04? I've used supervisord in the past to auto start web apps. ...
106
votes
7answers
91k views

Can anyone explain precisely what IOWait is?

As much as I have read about iowait, it is still mystery to me. I know it's the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also ...
93
33
votes
6answers
75k views

Is there a global, persistent CMD history?

Sometimes I forget how the exact syntax of a CMD command looks and then I would like to search my own CMD history. Clearly, within the same session, you can browse it with the up and down arrow keys ...
70
votes
1answer
87k views

InnoDB: Error: log file ./ib_logfile0 is of different size

I just added the following lines in /etc/mysql/my.cnf after I converted one database to use InnoDB engine. innodb_buffer_pool_size = 2560M innodb_log_file_size = 256M innodb_log_buffer_size = 8M ...
4
votes
3answers
57k views

What is a Cisco BVI interface? What is it used for?

I have been Google'd and searched for the answer to these questions, but I cannot find a simple answer. So my questions are about BVI interfaces. What are they? Why do you use them? In what scenario ...
4
votes
4answers
72k views

How do I get SonicWALL Global VPN to work with Windows 8.1?

I have been running SonicWALL Global VPN v4.7.3.0403 on Windows 8 without trouble for more than a year. Today I upgraded to Windows 8.1 RTM and noticed that it disabled my Global VPN connection. I ...
45
votes
5answers
16k views

On a dual CPU server, is it normal for one CPU to run hotter than the other?

I have a dual Opteron server running Linux with libvirt to host several VMs. The VMs work fine and the server processes OK, but I notice one CPU always runs about 69C (throttles at 70C) and the other ...
54
votes
9answers
133k views

Creating a virtual machine in VirtualBox from a physical one

Is there any way to create a virtual machine that you can use in VirtualBox from a physical installation that you have? For instance, if I have Windows XP installed on a physical computer and want to ...
130
votes
2answers
59k views

How can I see which flags Nginx was compiled with?

How can I check what modules have been added to an nginx installation?
98
14
votes
11answers
82k views

IIS/SMTP - emails are stuck in mailroot/Queue

I'm trying to send e-mails via SMTP within the IIS pickup directory. Unfortunately the e-mails are just going into the mailroot/queue folder and stay there. They never actually get sent. Does ...
90
52
votes
6answers
88k views

How to send emails and avoid them being classified as spam?

This is a canonical question about how to handle email sent from your server being misclassified as spam. For additional information you may find these similar questions helpful: Best ...
24
votes
5answers
94k views

How do I list all users with root?

On a linux box, how do I list all users that have root priveleges (and even better, all users in general along with if they have root or not)?
14
votes
5answers
125k views

Where are my Tomcat Logs?

I installed Tomcat6 on a Ubuntu 9.04 server using apt-get install tomcat6. I uploaded a WAR using the manager interface and tried to start the application but get a pretty generic error on the Web ...
30
votes
8answers
43k views

How to fix PuTTY showing garbled characters?

Connecting from a Windows 7 PC via SSH to an Ubuntu server using PuTTY, I get some screen errors: I.e. it: "Double-draws" the selection inside Midnight Commander (MC). Other characters like line ...
56
votes
12answers
31k views

How can I run arbitrarily complex command using sudo over ssh?

I have a system that I can only log in to under my username (myuser), but I need to run commands as other user (scriptuser). So far, I have come up with the following to run the commands I need: ssh -...
31
votes
7answers
47k views

Is it possible for two hostnames share the same IP address?

Can anyone explain whether it is possible for two hostnames to share the same IP address? And what about if one hostname represents more than one IP address, is that possible too? Why?
38
votes
8answers
68k views

How to add a timestamp to bash script log?

I have a constantly running script that I output to a log file: script.sh >> /var/log/logfile I'd like to add a timestamp before each line that is appended to the log. Like: Sat Sep 10 21:...
17
votes
4answers
74k views

How to save and exit crontab -e?

How to save and exit crontab -e? i tried every method listed here and none works, i have a centos 5, vi comes by default with yum and i installed nano Solved just changed the default editor export ...
6
votes
6answers
93k views

How do I completely remove MySQL from a linux installation?

I was surprised to find that one of my privileged users installed MySQL on a linux box. The server (mysqld) is running and doing nothing. My skills are all in Oracle, so I am unfamiliar with how to ...
66
votes
8answers
143k views

What limits the maximum number of connections on a Linux server?

What kernel parameter or other settings control the maximum number of TCP sockets that can be open on a Linux server? What are the tradeoffs of allowing more connections? I noticed while load testing ...
39
votes
8answers
78k views

How do I check the postfix queue size?

What's the postfix equivalent to sendmail -bp?
93
41
votes
6answers
56k views

Why do ethernet cables have 8 wires?

This might seem a stupid question but why do Ethernet cables have 8 wires? Cat5 cables were just using 4 of the 8 wires, so only 4 are actualy 'needed'. Why not 12 or 16 wires?
27
votes
4answers
53k views

IIS complains about a locked section - how can I find out where it's locked?

I have this section in my web.config: <system.webServer> <modules runAllManagedModulesForAllRequests="true" /> <security> <authentication> <...