Greatest Hits

184
votes
20answers
146k views

How can I run a server on Linux on port 80 as a normal user?

I have googled about it for quite some time, but couldn't find it. I am on Ubuntu Linux and want to run a server on port 80, but due to security mechanism of Ubuntu, I get the following error: ...
280
49
votes
5answers
222k views

What's the difference between Windows Server 2008, 2008 SP2 and 2008 R2?

What are the major differences between Windows Server 2008, 2008 SP2 and 2008 R2? Are the code bases for these OSes different? If I'm developing applications for any one of these three, should I be ...
135
votes
16answers
204k views

How to use rsync over FTP

Any unix: I have the following cmd line which works fine. rsync -avr -e ssh /home/dir user@example.com:/home/ But I need to set it up now to rsync to a remote server that only has an FTP server on ...
233
72
votes
11answers
191k views

How do you restart php-fpm?

I need to reload my php.ini and there's nothing in the help dialog about restarting it.
78
votes
2answers
80k 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 ...
209
votes
2answers
76k views

What exactly do the colors in htop status bars mean?

By default, htop shows colored status bars for processors, memory, and swap. From left to right, the bars are colored green, blue, yellow, and red depending on some thresholds. What does it mean when ...
19
votes
10answers
125k views

Get list of AD groups a user is a member of

Suppose I have the user id of a user in Active Directory. I'd like to get a list of all AD groups in which that user is currently a member of. How can I do this from the Windows command line? I've ...
15
votes
4answers
101k views

What's the difference between a Layer 2 & Layer 3 switch

What's the difference between a Layer 2 & Layer 3 switch? I've always wondered and never needed to know until now.
26
votes
13answers
259k views

How to get a list of all IP addresses (and ideally device names) on a LAN?

Our network gave an error that there was an IP address conflict and I'd like to find what all the device IP addresses are. (I've also had need of that before). (update/clarification:I'm looking for a ...
140
votes
4answers
141k views

What's the difference between ip address 0.0.0.0 and 127.0.0.1?

I do know that 127.0.0.1 ~ 127.255.255.254 are the loopback IP addresses for most modern operating systems and we could use these IP addresses to refer to our own computer. But what's 0.0.0.0? It ...
18
votes
6answers
33k views

How to fix corrupted opencl.dll in Windows 10, if SFC and DISM are failing?

It took me several hours to fix the issue because the local component store was corrupted and the computers are accessing a local WSUS server instead of the public update server by Microsoft (and ...
204
votes
6answers
209k views

How to assign permissions to ApplicationPoolIdentity account

In IIS 7 on Windows Server 2008, application pools can be run as the "ApplicationPoolIdentity" account instead of the NetworkService account. How do I assign permissions to this "...
10
votes
8answers
79k views

Can't start CentOS 7 “network” service

I Can't start CentOS 7 "network" service after disabling and removing "NetworkManager" service. When I check the network service status, it comes up with the following error: #systemctl status ...
29
votes
4answers
243k views

How to check who is currently logged on to windows workstation from command line?

Environment is in domain, server is Windows Server 2003, workstations have Vista and XP installed. I need the way to check remotely who is currently logged on workstation, preferably from some simple ...
102
votes
4answers
136k views

Why is my crontab not working, and how can I troubleshoot it?

This is a Canonical Question about using cron & crontab. The answer for 'Why is my crontab not working, and how can I troubleshoot it?' can be seen below. This addresses the cron system with ...
172
61
votes
9answers
115k views

hosts file ignored, how to troubleshoot?

The hosts file on Windows computers is used to bind certain name strings to specific IP addresses to override other name resolution methods. Often, one decides to change the hosts file, and discovers ...
102
votes
11answers
130k 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 ...
164
votes
5answers
259k views

MySQL: Bind to more than one IP address?

Is there a secret way to bind MySQL to more than one IP address? As far as I can see the bind-address parameter in the my.cnf does not support more than one IP and you can't have it more than once.
46
votes
2answers
154k views

Can I have multiple DHCP servers on one network?

This is a Canonical Question about Redundant DHCP Servers. Is it possible to have more than one DHCP server on the same LAN? What are the implications of doing this? What happens if there is more ...
206
votes
10answers
103k views

How to tell which local branch is tracking which remote branch in Git?

I would like to know if there's a way to tell which local branch is tracking which remote branch in Git. I'm using one remote server, which is named "origin".
252
105
votes
10answers
202k views

How to refresh hosts file without rebooting

On Windows, how do you refresh the hosts file without rebooting?
204
73
votes
6answers
157k views

Find name of Active Directory domain controller

How can I find out the name/IP address of the AD domain controller on my network?
109
votes
6answers
159k views

How do you add a Windows environment variable without rebooting?

This is probably an easy answer, but I have never been able to find it by googling. I simply would like to add an Environment variable to a Windows machine (desktop or server) and be able to use it ...
141
votes
8answers
161k views

How do I share a Git repository with multiple users on a machine?

I have a Git repository on a staging server which multiple developers need to be able to pull to. git-init seems to have a flag very close to what I'm looking for: --shared, except I'd like multiple ...
25
votes
7answers
124k views

How do I remove login credentials for a network location in Win7?

I just tried to access a folder like so: \\somecomputeronmynetwork\somelocation$ When going to this location I'm prompted for a user name and password. I put one in, and it let me in fine. Now I ...
102
votes
5answers
132k views

how to download the ssl certificate from a website?

I want to download the ssl certificate from, say https://www.google.com, using wget or any other commands. Any unix command line? wget or openssl?
138
votes
13answers
152k views

Copying a large directory tree locally? cp or rsync?

I have to copy a large directory tree, about 1.8 TB. It's all local. Out of habit I'd use rsync, however I wonder if there's much point, and if I should rather use cp. I'm worried about permissions ...
99
votes
3answers
91k views

Meaning of the buffers/cache line in the output of free

Why does my server show total used free shared buffers cached Mem: 12286456 11715372 571084 0 81912 6545228 -/+ buffers/cache: 5088232 7198224 Swap:...
11
votes
10answers
105k views

How to remotely see what users are logged into Windows 7 or Vista

I need to login to a remote into either a Win7 or Vista computer but when I connect I get a Logon Message "Another user is currently logged on..." but it does not specify who. I have a domain ...
23
votes
4answers
117k views

Best way to gracefully restart CentOS?

I always used the command: shutdown -r now However, sometimes that causes MySQL issues. What's the most graceful way to restart CentOS? I've seen: reboot and halt How can I gently reboot ...
1
vote
5answers
94k views

Windows Server 2012 r2 Standard Activation Issue - MAK license

I am trying to activate MS Server 2012 R2 Standard and I'm having issues. I have installed the software from the ISO file I downloaded from the volume licensing site. I have learned that this file ...
106
votes
7answers
126k views

Can I automatically add a new host to known_hosts?

Here's my situation: I'm setting up a test harness that will, from a central client, launch a number of virtual machine instances and then execute commands on them via ssh. The virtual machines will ...
31
votes
6answers
150k views

How do I access the list of currently logged on users through Terminal Services Manager in Windows Server 2012?

In Windows 2003 and 2008 we had Terminal Services Manager (see screenshot below). However in Windows server 2012 it's gone. Does anyone know how to access the list of currently remotely logged on ...
58
votes
8answers
96k views

How can I kill all stopped jobs?

When I try to exit from my Linux server I get the message: There are stopped jobs. : Is there a single command to kill these?
230
35
votes
5answers
196k 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.
66
votes
10answers
214k views

Run Oracle SQL script and exit from sqlplus.exe via command prompt

I would like to run an Oracle script through SQL Plus via a Windows command prompt. The script does not contain an "exit" command, but I would still like SQL Plus to exit, returning control to the ...
37
votes
8answers
202k views

How to check the physical status of an ethernet port in Linux?

I want to check if a specified ethX is physically up or down. How do I do that with the command line?
42
votes
8answers
111k views

Why is the response on localhost so slow?

I am working on a tiny little PHP project for a friend of mine, and I have a WAMP environment setup for local development. I remember the days when the response from my local Apache 2.2 was immediate. ...
62
votes
8answers
114k views

How to Unban an IP properly with Fail2Ban

I'm using Fail2Ban on a server and I'm wondering how to unban an IP properly. I know I can work with IPTables directly: iptables -D fail2ban-ssh <number> But is there not a way to do it with ...
107
votes
3answers
54k 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/ ...
328
votes
6answers
98k views

How does IPv4 Subnetting Work?

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it by ...
111
votes
10answers
158k views

How do I get current Unix time in milliseconds using bash?

How do I get the current Unix time in milliseconds (i.e number of milliseconds since Unix epoch January 1 1970)?
181
65
votes
13answers
173k views

Using wget to recursively download whole FTP directories

I want to copy all of the files and folders from one host to another. The files on the old host sit at /var/www/html and I only have FTP access to that server, and I can't TAR all the files. Regular ...
81
votes
6answers
164k 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 ...
70
votes
6answers
260k views

How can I read pcap files in a friendly format?

a simple cat on the pcap file looks terrible: $cat tcp_dump.pcap ?ò????YVJ? JJ ?@@.?E<??@@ ?CA??qe?U????иh? .Ceh?YVJ?? JJ ?@@.?E<??@@ CA??qe?U????еz?...
32
votes
7answers
99k views

How can I edit the welcome message when ssh start?

I have a vps for my website hosting. It is running a ubuntu server. Every time I logged in my server by ssh, it displays a lengthy welcome message in my terminal. Linux node61.buyvm.net 2.6.18-...
55
votes
17answers
66k views

`mysql_upgrade` is failing with no real reason given

I'm upgrading from MySQL 5.1 to 5.5, running mysql_upgrade and getting this output: # mysql_upgrade Looking for 'mysql' as: mysql Looking for 'mysqlcheck' as: mysqlcheck FATAL ERROR: Upgrade failed ...
185
votes
3answers
133k 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 ...
73
votes
7answers
129k 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.
23
votes
4answers
143k views

How to delete domain user profile from a computer?

I'm wondering how to safely remove a domain user profile from a computer that is a part of a domain. I don't want to delete the account from the domain itself, I just need to remove the profile from ...