Greatest Hits

74
votes
7answers
133k views

how to check if a library is installed?

In linux, how do I check if a library is installed or not? (from the command line of course). In my specific case now, I want to check whether libjpeg is installed.
185
votes
3answers
134k views

What's the best way of handling permissions for apache2's user www-data in /var/www?

Has anyone got a nice solution for handling files in /var/www? We're running Name Based Virtual Hosts and the apache2 user is www-data. We've got two regular users & root. So when messing with ...
61
votes
3answers
102k 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 ...
33
votes
5answers
247k 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 ...
16
votes
1answer
72k 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) ...
96
votes
10answers
110k 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 ...
220
44
votes
8answers
80k views

On IIS, how do I patch the SSL 3.0 POODLE vulnerability (CVE­-2014­-3566)?

How do I patch CVE­-2014­-3566 on a Windows Server 2012 system running IIS? Is there a patch in Windows Update, or do I have to do a registry change to disable SSL 3.0?
159
votes
2answers
72k 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 ...
19
votes
2answers
99k 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 ...
93
votes
5answers
262k 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 ...
98
votes
11answers
111k views

How to zip/unzip files in Powershell?

Is there a one-liner that will zip/unzip files (*.zip) in PowerShell?
24
votes
2answers
46k 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 ?
101
votes
16answers
92k 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 ...
196
18
votes
11answers
228k 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 ...
75
votes
5answers
207k 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 192....
27
votes
12answers
149k 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.
29
votes
12answers
92k 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 couldn'...
96
votes
14answers
117k 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 ...
49
votes
6answers
114k 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 ? ...
71
votes
6answers
56k 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?
27
votes
5answers
170k 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?
37
votes
7answers
55k 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 ...
25
votes
4answers
221k 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
6answers
146k 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 ...
79
votes
3answers
118k 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?
45
votes
3answers
93k 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 ...
150
74
votes
7answers
103k 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. ...
16
votes
3answers
93k 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 ...
14
votes
7answers
141k 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 ...
35
votes
7answers
169k 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 ...
114
votes
9answers
122k 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 ...
15
votes
10answers
110k 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?
39
votes
5answers
72k views

What is the difference between SAN, NAS and DAS?

What is the difference between SAN, NAS and DAS?
50
votes
2answers
196k 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 ...
104
27
votes
12answers
99k 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).
36
votes
10answers
151k views

Windows server last reboot time

How can I find a Windows server's last reboot time, apart from 'net statistics server/workstation'?
131
34
votes
8answers
67k 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 ...
34
votes
14answers
88k 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 ...
53
votes
14answers
166k 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 ...
129
votes
14answers
77k views

How do diff over ssh?

How do I diff files/folders across machines provided that the only connectivity available is ssh?
190
125
votes
8answers
105k 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 ...
39
votes
11answers
101k 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 ...
47
votes
8answers
98k 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 space....
88
votes
3answers
13k views

Smell of rotten eggs in the server room

A week ago I got the following error on my APC Smart-UPS 1000 which I muted. Warning State: Connect battery Load: 55% Batt: 100% Today, I could smell a sort of sulfur/sulphur/rotten egg smell when ...
41
votes
9answers
150k 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 ...
77
votes
3answers
103k 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 ...
20
votes
10answers
129k 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 ...
39
votes
4answers
111k views

VirtualBox: How to set up networking so both host and guest can access internet and talk to each other

I was wondering if someone could give me a simple guide on how to set up virtual networking in VirtualBox (4.0.2) so that the following scenarios work: Both Host and Guest can access Internet Host ...
18
votes
2answers
25k views

How can I upgrade to Java 1.8 on an Amazon Linux Server?

I tried sudo yum update but it just keeps java "1.7.0_75". I need 1.8 for it to work with another application but can't figure out how to upgrade it. Do I need to manually install it somehow? There's ...
110
votes
14answers
100k 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 ...