Greatest Hits

16
votes
10answers
138k 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 ...
19
votes
10answers
96k 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: ...
8
votes
6answers
64k 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 ...
5
votes
3answers
80k 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 ...
45
votes
6answers
83k views

How do I verify the speed of my NIC?

I just installed a new gigabit network interface card (NIC) in Linux. How do I tell if it is really set to gigabit speeds? I see ethtool has an option to set the speed, but I can't seem to figure ...
20
votes
7answers
95k 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 ...
15
votes
4answers
69k 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 ...
22
votes
2answers
62k views

How does ServerName and ServerAlias work?

It's the following part of a virtual host config that I need further clarification on: <VirtualHost *:80> # Admin email, Server Name (domain name), and any aliases ServerAdmin ...
23
votes
12answers
78k views

How to recover from “Too many Authentication Failures for user root”

I've done several attempts to establish SSH-connecton for user root@host using putty terminal. While doing so I specified wrong credentials several times and after that I've specified them correctly, ...
98
4
votes
4answers
33k 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. ...
27
votes
6answers
40k 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 ...
40
votes
7answers
149k views

Where to check log of sendmail?

I can't send out emails, need to look into the logs, but where is the log?
29
votes
6answers
77k 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: ...
22
votes
1answer
19k views

What causes the 'Connection Refused' message?

This is a Canonical Question about Connection Refused We see a lot of questions to the effect When I try to connect to a system I get a message Connection refused Why is this ?
4
votes
3answers
54k 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 ...
33
votes
2answers
93k 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?
43
votes
5answers
103k 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 ...
27
votes
6answers
66k 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.
5
votes
7answers
104k 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 ...
8
votes
3answers
50k 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 ...
101
16
votes
4answers
22k views

How do I patch RHEL 4 for the bash vulnerabilities in CVE-2014-6271 and CVE-2014-7169?

A mechanism for remote code execution through Bash has been widely reported yesterday and today (September 24, 2014.) http://seclists.org/oss-sec/2014/q3/650 Reported as CVE-2014-7169 or CVE-2014-6271 ...
4
votes
4answers
71k 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 ...
64
votes
4answers
92k 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 ...
68
votes
1answer
83k 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 ...
54
votes
9answers
130k 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 ...
37
votes
3answers
71k 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 ?
79
votes
8answers
39k views

Heartbleed: how to reliably and portably check the OpenSSL version?

I was looking at a reliable and portable way to check the OpenSSL version on GNU/Linux and other systems, so users can easily discover if they should upgrade their SSL because of the Heartbleed bug. ...
20
votes
7answers
44k 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 ...
16
votes
7answers
57k 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 ...
26
votes
5answers
78k 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 ...
7
votes
1answer
16k views

Default browser opens to msn.com when logging into Windows Server

I installed a fresh Windows Server 2012 R2 Standard with GUI instance on a VMware VM. The first time I logged in as Administrator, I noticed an Internet Explorer window automatically opened to ...
31
votes
6answers
69k 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 ...
52
votes
6answers
84k 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 ...
101
votes
7answers
85k 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 ...
87
30
votes
14answers
76k views

Why does “Loading your personal settings” take forever?

I have come across dozens of user installations of Windows (XP) where, after logging in, the system stays stuck on this screen for a very long time. What are the possible causes? How can I diagnose ...
93
53
votes
12answers
29k 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 ...
38
votes
3answers
38k 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. ...
66
votes
8answers
139k 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 ...
11
votes
5answers
122k views

How do I increase the maximum number of concurrent remote connections in Windows Server 2003?

I am trying to allow more than the default of 2 concurrent remote connections to a server running Windows Server 2003. Background: I went to "Start" => "Administration Tools" => "Terminal Services ...
14
votes
1answer
41k views

Managing CBS.log files on Windows 2008R2?

Whilst auditing disk space on our Windows 2008R2 farm we noticed that some servers had quite large C:\Windows\Logs\CBS\CBS.log files (~1.5GB). I was under the impression that this particular log file ...
6
votes
6answers
90k 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 ...
23
votes
5answers
89k 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
118k 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 ...
126
votes
2answers
56k views

How can I see which flags Nginx was compiled with?

How can I check what modules have been added to an nginx installation?
93
30
votes
6answers
22k 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 ...
13
votes
11answers
76k 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 ...
86
72
votes
2answers
109k views

How to Configure Windows Machine to Allow File Sharing with DNS Alias

What process is necessary to configure a Windows environement to allow me to use DNS CNAME to reference servers? I want to do this so that I can name my servers something like SRV001, but still have ...
41
votes
6answers
53k 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?
39
votes
8answers
75k views

How do I check the postfix queue size?

What's the postfix equivalent to sendmail -bp?
88
31
votes
6answers
43k 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?