87
votes
8answers
101k views

Dump Microsoft SQL Server database to an SQL script

Is there any way to export a Microsoft SQL Server database to an sql script? I'm looking for something which behaves similarly to mysqldump, taking a database name, and producing a single script ...
86
votes
5answers
174k 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 ...
86
votes
21answers
17k views

Why should I firewall servers?

PLEASE NOTE: I'm not interested in making this into a flame war! I understand that many people have strongly-held beliefs about this subject, in no small part because they've put a lot of effort into ...
85
votes
11answers
106k views

Finding out what user Apache is running as?

I want to secure a file upload directory on my server as described beautifully here, but I have one problem before I can follow these instructions. I don't know what user Apache is running as. I've ...
85
votes
3answers
74k views

how to disable SSH login with password for some users?

On Linux (Debian Squeeze) I would like to disable SSH login using password to some users (selected group or all users except root). But I do not want to disable login using certificate for them. ...
85
votes
2answers
15k views

Can you help me with my capacity planning?

This is a Canonical Question about Capacity Planning Related: How do you do Load Testing and Capacity Planning for Web Sites? How do you do Load Testing and Capacity Planning for ...
84
votes
9answers
93k 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 ...
84
votes
13answers
101k 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 ...
84
votes
15answers
77k 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 ...
84
votes
8answers
91k views

how to set global PATH on OS X?

I'd like to append to the global PATH variable on OS X so that all user shells and GUI applications get the same PATH environment. I know I can append to the path in shell startup scripts, but those ...
83
votes
12answers
10k views

Transfer 10TB of files from USA -> UK datacenter

I am migrating my server from the USA to the UK from one data center to another, my host said I should be able to achieve 11 megabytes per second. Operating system is Windows Server 2008 at both ...
83
votes
5answers
31k views

How do I rename a task in Task Scheduled on Windows Server 2008 R2

I have some tasks in the Task Scheduler on Windows 2008 R2. I created them as the admin and I'm logged in as the admin. I have no easy way to rename the tasks. The only way I can is to export the task ...
82
votes
11answers
89k views

How to know from which yum repository a package has been installed?

After I have installed a package by yum (with multiple repositories configured), how can I find from which repository it has been installed? If I run yum info package-name (or yum list package-name), ...
82
votes
5answers
51k views

How to change an EC2 instance's security group

I have created a new EC2 instance. It got assigned the default security group. I want to change that security group. How?
81
votes
8answers
11k views

How can a single disk in a hardware SATA RAID-10 array bring the entire array to a screeching halt?

Prelude: I'm a code-monkey that's increasingly taken on SysAdmin duties for my small company. My code is our product, and increasingly we provide the same app as SaaS. About 18 months ago I moved ...
80
votes
3answers
42k views

ssh hostname returns “Bad owner or permissions on ~/.ssh/config”

When I try to ssh to another box, I get this strange error $ ssh hostname Bad owner or permissions on ~/.ssh/config But I made sure that I own and have rw permissions on the file: ls -la ~/.ssh/ ...
80
votes
6answers
152k views

Boot and Install Windows from a USB thumb drive

Installing Windows from a thumb drive is vastly superior to burning a copy to a DVD which will fill some landfill somewhere with toxic stuff. Not to mention it's about 50x faster to install Windows ...
79
votes
7answers
115k views

How to forcibly close a socket in TIME_WAIT?

I run a particular program on linux which sometimes crashes. If you open it quickly after that, it listens on socket 49201 instead of 49200 as it did the first time. netstat reveals that 49200 is in ...
79
votes
11answers
16k views

How bad is it really to install Linux on one big partition?

We will be running CentOS 7 on our new server. We have 6 x 300GB drives in raid6 internal to the server. (Storage is largely external in the form of a 40TB raid box.) The internal volume comes to ...
79
votes
13answers
21k views

Are networks now faster than disks?

This is a software design question I used to work on the following rule for speed cache memory > memory > disk > network With each step being 5-10 times the previous step (e.g. cache ...
79
votes
4answers
14k views

Why is TCP accept() performance so bad under Xen?

The rate at which my server can accept() new incoming TCP connections is really bad under Xen. The same test on bare metal hardware shows 3-5x speed ups. How come this is so bad under Xen? Can you ...
78
votes
13answers
32k views

Why is RAID not a backup?

When someone mentions RAID in a conversation about backups, invariably someone declares that "RAID is not a backup." Sure, for striping, that's true. But what's the difference between redundancy and ...
78
votes
17answers
45k views

Should network hardware be set to “autonegotiate” speeds or fixed speeds?

We recently had a little problem with networking where multiple servers would intermittently lose network connectivity in a fairly painful-to-resolve way (required hard reboot). This has been going on ...
78
votes
9answers
464k 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 ...
78
votes
4answers
26k views

How do you do load testing and capacity planning for web sites?

This is a canonical question about capacity planning for web sites. Related: Can you help me with my capacity planning? How do you do Load Testing and Capacity Planning for ...
78
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. ...
77
votes
13answers
28k views

Is Ping a reliable way to check if a server is available?

In my application I am pinging a server and waiting for a response. I am using this to determine whether the server is available and responsive or not. Is this a reliable way of determining ...
76
votes
9answers
55k views

How to stop people from using my domain to send spam? [duplicate]

I receive Mailer Daemon messages saying certain emails fail. My domain is itaccess.org which is administered by Google apps. Is there any way I can identify who is sending emails from my domain, and ...
76
votes
8answers
73k views

How much network latency is “typical” for east - west coast USA?

At the moment we're trying to decide whether to move our datacenter from the west coast to the east coast. However, I am seeing some disturbing latency numbers from my west coast location to the east ...
76
votes
6answers
146k views

List all DNS records in a domain using dig?

My company runs an internal DNS for mycompany.com There is a machine on the network that I need to find, but I’ve forgotten its name. If I could see a list, it would probably jog my memory. How ...
74
votes
1answer
17k views

Why do I need Nginx and something like Gunicorn?

Im looking for a overly simplified answer for the following question. Im trying to build a foundational understanding of how Nginx works along side something like GUnicorn. Do I need both Nginx and ...
74
votes
4answers
33k views

What is a glue record?

This is a Canonical Question about DNS glue records. What exactly (but briefly) is a DNS glue record? Why are they needed and how do they work?
73
votes
5answers
49k views

Top level domain/domain suffix for private network?

At our office, we have a local area network with a purely internal DNS setup, on which clients all named as whatever.lan. I also have a VMware environment, and on the virtual-machine-only network, I ...
73
votes
2answers
69k views

How do VLANs work?

What are VLANs? What problems do they solve? I'm helping a friend learn basic networking, as he's just become the sole sysadmin at a small company. I've been pointing him at various questions/answers ...
73
votes
5answers
80k views

How to setup passwordless `sudo` on Linux?

How can passwordless sudo access be setup on either RHEL (Fedora, CentOS, etc) or Ubuntu distributions? (If it's the same across distros, that's even better!) Setting: personal and/or lab/training ...
73
votes
14answers
5k views

What's wrong with always being root?

I have a feeling this is a stupid question, but this is something I've wondered for awhile. I have a VPS and this is my first big linux venture. I am the only person who has access to it. My question ...
73
votes
8answers
11k views

How to backup 20+TB of data?

We have a NAS server at the company I work for that is being used for storing photography sessions. Each session is approximately 100gb. Over the last couple of years this server has accumulated 10+ ...
72
votes
4answers
160k 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
72
votes
6answers
33k views

Fighting Spam - What can I do as an: Email Administrator, Domain Owner, or User?

This is a Canonical Question about Fighting Spam. Also related: How to stop people from using my domain to send spam? What are SPF records, and how do I configure them? There are ...
72
votes
5answers
12k views

Tips for Securing a LAMP Server

This is a Canonical Question about Securing a LAMP stack What are the absolute guidelines for securing a LAMP server?
72
votes
3answers
46k views

What is archive mode in rsync?

I know you can use -a or --archive to activate archive mode when using rsync. Unfortunately, I have no idea what archive mode is supposed to do, and the man page is not at all explicit about what this ...
72
votes
2answers
22k views

Amazon EC2 terminology - AMI vs. EBS vs. Snapshot vs. Volume

I have been poking around Amazon EC2, and am a little confused on some of the terminology. Specifically with regard to AMI, snapshots and volumes, and an EBS Please correct me if I am wrong, or fill ...
71
votes
9answers
14k views

Linux - Is there a way to prevent/protect a file from being deleted even by root?

I have a very important file which an application in my workplace uses, i need to make sure it is not delete whatsoever, how can I do that?
71
votes
7answers
95k 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. ...
71
votes
3answers
90k 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 ...
71
votes
9answers
55k views

Is it possible to detach a process from its terminal? (Or, “I should have used screen!”) [duplicate]

Possible Duplicate: Can I nohup/screen an already-started process? On Unix (specifically, Linux), I've started a job in a regular ssh->bash session. I'd like to leave work soon, but I now ...
71
votes
6answers
54k 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?
71
votes
1answer
41k views

How do I change my private key passphrase?

I have an existing public/private key pair, the private key is password protected, the encryption may be either RSA or DSA. These keys are the kind you generate with ssh-keygen and generally store ...
71
votes
1answer
15k views

What happens when you plug two sides of a cable to a single networking device?

What is likely to happen when you plug two ends of a network cable to a single switch/router? Will this create problems on the network, or just be ignored?
71
votes
2answers
106k 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 ...

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