Greatest Hits

50
votes
3answers
118k views

DNS - NSLOOKUP what is the meaning of the non-authoritative answer?

When I do a NS Lookup, for some domains I get the reply saying Non-authorative answer:. I want to know what it means? Got answer: HEADER: opcode = QUERY, id = 3, rcode = NXDOMAIN ...
31
votes
5answers
180k views

Resolve host name from IP address

I'm looking for a command line tool which gets an IP address and returns the host name, for Windows.
33
votes
5answers
239k views

How to correct Postfix' 'Relay Access Denied'?

This morning, in order to correct a problem with a name mismatch in the security certificate, I followed the recommended steps from How to fix mail server SSL?, but now, when attempting to send an ...
58
votes
3answers
96k views

What is the difference between unicast, anycast, broadcast and multicast traffic?

I have never had the privilege of working in an environment that required complicated routing or if it did require it, it was handled upstream of me. I've always used very simple static routing ...
92
votes
5answers
255k views

Does Windows have a built-in ZIP command for the command line?

Since Windows Explorer (since at least Windows XP) has some basic support for ZIP files, it seems like there should be a command-line equivalent, but I can't seem to find any sign of one. Does ...
92
votes
9answers
104k views

Shell command to monitor changes in a file - What's it called again?

I know there was a command on Unix that I could use to monitor a file and see changes that are getting written to it. This was quite useful especially for checking log files. Do you know what it is ...
209
97
votes
11answers
108k views

How to zip/unzip files in Powershell?

Is there a one-liner that will zip/unzip files (*.zip) in PowerShell?
71
votes
6answers
55k views

How to test if my server is vulnerable to the ShellShock bug?

How can I ensure my Bash installation is not vulnerable to the ShellShock bug anymore after the updates?
15
votes
1answer
66k views

How to stop ping output?

I run ping <hostname> command in console and it now outputs hundreds of those rows now (icmp_seq=526 ttl=64 time=0.026 ms), icmp_seq is like 500 or more now. How to stop it? (linux debian) ...
151
votes
2answers
68k views

How do I select which Apache MPM to use?

I'm a little confused between the different MPMs offered by Apache - 'worker', 'event', 'prefork', etc. What are the major differences between them, and how can I decide which one will be best for a ...
18
votes
11answers
220k views

How can I find out if a port is opened or not?

I have installed Apache server on my Windows 7 computer. I was able to display the default index.php by typing http://localhost/ in the address line of my browser. However, I am still unable to see ...
122
votes
22answers
89k views

How can I get the size of an Amazon S3 bucket?

I'd like to graph the size (in bytes, and # of items) of an Amazon S3 bucket and am looking for an efficient way to get the data. The s3cmd tools provide a way to get the total file size using s3cmd ...
72
votes
5answers
200k views

How can I port forward with iptables?

I want connections coming in on ppp0 on port 8001 to be routed to 192.168.1.200 on eth0 on port 8080. I've got these two rules -A PREROUTING -p tcp -m tcp --dport 8001 -j DNAT --to-destination ...
26
votes
12answers
144k views

How to find out details about hardware on the Linux machine?

-i.e - how to get a full list of hardware components in command line (on a machine with no window system) Thank you.
96
votes
16answers
86k views

Showing total progress in rsync: is it possible?

I have searched for this option already, but have only found solutions that involve custom patching. The fact that it does not show in --help and no more info can be found probably indicates the ...
187
18
votes
2answers
88k views

What's the best way to see logged in users on Windows Server 2012?

Right now I use a powershell script to see the currently logged in users. But I don't see if there session is idle, active or inactive. I can see when the session was started but that's it. Is there a ...
23
votes
4answers
216k views

How to find time server in a domain?

In a Windows domain PDC isn't necessarily the domain time server. How could I identify the authoritative time server?
45
votes
3answers
91k views

How do I upgrade from PHP 5.3 to PHP 5.4.6 in Ubuntu?

Is there an easy way out to get the latest PHP? I have tried updating my package but none of it has 5.4.6 yet... if anyone knows on how to do it quickly, can it be shared here? I've tried compiling ...
149
16
votes
3answers
89k views

CentOS 7 Firewall Configuration

In CentOS 6 I could type setup from the command line and I would be presented with a set of tools, one of them being Firewall configuration. I can still do this in CentOS 7, except the list no longer ...
93
votes
14answers
111k views

How to reconnect to a disconnected ssh session

Is there a way to connect to an ssh session that was disconnected? We are having problems with our network connection to a remote site that we are working on separately; however, in the mean time we ...
13
votes
7answers
138k views

How to resolve a “driver failure” error in the Cisco VPN client connecting from a Windows 7 client

I have recently upgraded my laptop from Windows Vista SP1 to Windows 7 Professional. After the upgrade, if I try to use the Cisco VPN client to connect to a network, I get this message: Secure VPN ...
43
votes
6answers
105k views

How do I sleep for a millisecond in bash or ksh

sleep is a very popular command and we can start sleep from 1 second: # wait one second please sleep 1 but what the alternative if I need to wait only 0.1 second or between 0.1 to 1 second ? ...
74
votes
7answers
101k views

How to determine JAVA_HOME on Debian/Ubuntu?

On Ubuntu it is possible to have multiple JVMs at the same time. The default one is selected with update-alternatives. But this does not set the JAVA_HOME environment variable, due to a debian policy. ...
24
votes
5answers
161k views

Which ports do I need to open in the firewall to use NFS?

I'm running Ubuntu 11.10 - setting up NFS to share a directory among many other servers. Which ports are required to be opened on the firewall?
76
votes
3answers
113k views

Is there a way to view the members of an Active Directory group if you aren't a domain admin and can't log into to a domain controller?

Is there a way to view the members of an Active Directory group if you aren't a domain admin and can't log into to a domain controller?
34
votes
7answers
163k views

Disable password complexity rule in Active Directory

Where do I go to disable the password complexity policy for the domain? I've logged onto the domain controller (Windows Server 2008) and found the option in local policies which is of course locked ...
43
votes
6answers
135k views

Proxy Error 502 “Reason: Error reading from remote server” with Apache 2.2.3 (Debian) mod_proxy and Jetty 6.1.18

Apache is receiving requests at port :80 and proxying them to Jetty at port :8080 The proxy server received an invalid response from an upstream server The proxy server could not handle the request ...
34
votes
7answers
47k views

How do I disable TLS 1.0 without breaking RDP?

Our credit card processor recently notified us that as of June 30, 2016 we will need to disable TLS 1.0 to remain PCI compliant. I tried to be proactive by disabling TLS 1.0 on our Windows Server 2008 ...
29
votes
12answers
83k views

Unable to install .net 3.5 on Windows server 2012

I am trying to install .Net 3.5 on Windows Server 2012 and it constantly keeps failing. I am using "Add or Remove Features" and my Internet is already there. I've read that if alternate source ...
15
votes
10answers
107k views

Windows File and Folder “Attributes” A or C

In Windows Server 2003, in the "Attributes" column of windows explorer, some files have "A" or "C" or "AC" or others. What do these mean?
108
votes
9answers
117k views

When does `cron.daily` run?

When do entries in cron.daily (and .weekly and .hourly) run, and is it configurable? I haven't found a definitive answer to this, and am hoping there is one. I'm running RHEL5 and CentOS 4, but for ...
123
votes
14answers
74k views

How do diff over ssh?

How do I diff files/folders across machines provided that the only connectivity available is ssh?
186
33
votes
14answers
86k views

What is a patch panel?

What is a patch panel? How it is different from (layer 2) switch? EDIT: I think my primary question (and confusion) is this: Why don't network connections go straight to the switch? Don't we still ...
49
votes
2answers
184k views

How to check sshd log?

I have Ubuntu 9.10 installed with sshd and i can successfully connect to it using login and password. I have configured an RSA key login and now have "Server refused our key" as expected. Ok, now i ...
100
39
votes
11answers
98k views

create home directories after create users

I created some users with: $ useradd john and I forgot to specify the parameter -m to create the home directory and to have the skeleton files copied to each user. now I want to do that, and I ...
121
votes
8answers
100k views

How can I run Debian stable but install some packages from testing?

Say you're running a server and you don't want to upgrade to Testing (Squeeze) from Stable (Lenny) to just install a required package or two. What's the best way of installing only certain packages ...
52
votes
14answers
160k views

What is the correct temperature for a server room?

When I was working in our server room, I noticed that it was very cold. I know that the server room has to be cold to offset the heat of the servers, but perhaps it is TOO cold. What is an ...
36
votes
5answers
68k views

What is the difference between SAN, NAS and DAS?

What is the difference between SAN, NAS and DAS?
75
votes
3answers
98k views

How to add dependency on a Windows Service AFTER the service is installed

I have a Windows Service that makes use of a SQL Server database. I don't have control over the installation of the service, but would like to add a dependency on the service to ensure that it starts ...
30
votes
6answers
62k views

Apache2 config variable is not defined

I installed apache2 on ubuntu 13.10. If I try to restart it using sudo /etc/init.d/apache2 restart I get this message: AH00558: apache2: Could not reliably determine the server's fully ...
58
votes
6answers
72k views

What does “Warning: untrusted X11 forwarding setup failed: xauth key data not generated” mean when ssh'ing with -X?

When I use ssh -X on my Mac (running OS X 10.6.7) to connect to my Ubuntu (11.04) box, I get the following warning: Warning: untrusted X11 forwarding setup failed: xauth key data not generated ...
26
votes
12answers
92k views

How do I know if I'm working on a Virtual Machine or not?

Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).
34
votes
10answers
137k views

Windows server last reboot time

How can I find a Windows server's last reboot time, apart from 'net statistics server/workstation'?
123
46
votes
8answers
91k views

df in linux not showing correct free space after file removal

I have file servers which are used to store files. Files might reside there for a week, or for a year. Unfortunately, when I remove files from the server, df command doesn't reflect the freed up ...
40
votes
9answers
141k views

How can I get a list of shared directories on local Windows server?

If I have a Windows server (typically 2000, 2003 or 2008), is there a simple way to list all local directories shared on that server? I can find the shares themselves easily enough, but I would love ...
30
votes
10answers
121k views

Group Policy installation failed error 1274

I'm trying to deploy an MSI via the Group Policy in Active Directory. But these are the errors I'm getting in the System event log after logging in: The assignment of application XStandard from ...
110
votes
14answers
97k views

In my /etc/hosts/ file on Linux/OSX, how do I do a wildcard subdomain?

I need to test sub-domains on my localhost. How can I effectively have this result of adding *.localhost.com to my /etc/hosts/ file? If it's not possible, how do I work around this problem? I need ...
44
votes
2answers
121k views

What are windows 7 N/KN/VL editions?

We're subscribed to MSDN at work and I've noticed that among the various windows "editions" there are downloads such as "Windows 7 Ultimate N" and "Windows 7 Ultimate N and KN". What are these ...
20
votes
10answers
120k views

SSL Error - unable to read server certificate from file

I've been setting up SSL for my domain today, and have struck another issue - I was hoping someone could shed some light on.. I keep receiving the following error messages: [error] Init: Unable to ...
7
votes
4answers
78k views

SSH: Permission denied (publickey,gssapi-with-mic,password)

==================================================================== UPDATE: It turned out the configuration of sshd on host2 wont allow password login. Thanks to people answered this. ...