7
votes
6answers
2k views

Loopback to forwarded Public IP address from local network - Hairpin NAT

This is a Canonical Question about Hairpin NAT (Loopback NAT). The generic form of this question is: We have a network with clients, a server, and a NAT Router. There is port forwarding on the ...
2
votes
3answers
6k views

FTP and Apache permission issues

Im having issues as to which user should own my www directory - ftp or apache? When set to the ftp user, the user can add, remoe and easily modify files but php file system actions generate permission ...
38
votes
15answers
3k views

What's your favorite ticketing system? [closed]

I'm in the market for a ticketing system and I'm curious what everyone else is using. I'd like to welcome everyone to post their favorite ticketing system and the reason they like it so much. My ...
11
votes
4answers
885 views

What am I looking for in a Monitoring Solution?

This is a Canonical Question about Monitoring Software. Also Related: What tool do you use to monitor your servers? I need to monitor my servers; what do I need to consider when deciding on ...
13
votes
3answers
1k views

Why not use a WAMP stack?

I recently had a talk with some experienced people and they suggested to me not to use a WAMP stack, and instead install apache, mysql and php separately. I don't understand why they have suggested ...
16
votes
4answers
16k views

How do I tell if my Windows server is swapping?

I'm using Process Explorer to monitor my windows server while it reconstructs some data. It's primarily a CPU intensive process, but I want to make sure it's not swapping. How can I tell if it is ...
30
votes
5answers
4k views

Are VMware ESXi 5 patches cumulative?

This seems basic, but I'm confused about the patching strategy involved with manually updating standalone VMware ESXi hosts. The VMware vSphere blog attempts to explain this, but the actual process is ...
15
votes
6answers
4k views

Avoid linux out-of-memory application teardown

I'm finding that on occasion my Linux box runs out of memory and it starts tearing down random processes to deal with it. I'm curious what administrators do to avoid this? Is the only real ...
158
votes
11answers
47k views

Can I nohup/screen an already-started process?

I'm doing some test-runs of long-running data migration scripts, over SSH. Let's say I start running a script around 4 PM; now, 6 PM rolls around, and I'm cursing myself for not doing this all in ...
47
votes
14answers
27k views

Top level domain for private networks?

On our office network we have an internal DNS and all the hostnames are whatever.lan. On my VMware VMs, on their host-only network I call them whatever.vm. We now have a private IP space network in ...
18
votes
23answers
26k views

Finding the Public IP address in a shell script

I can find my IP address using ifconfig or hostname -i command. But how do I find my Public IP? (I have a static public IP but I want to find it out using unix command)
18
votes
3answers
64k views

How to run VMWare ESX or ESXi in a virtual machine?

Can VMWare ESX or ESXi be installed and used inside a virtual machine? It can be installed inside VMWare Workstation or Server, but then it doesn't work; the main symptoms are: It runs REALLY ...
14
votes
17answers
8k views

Who is your favorite VPS Provider? [closed]

Who is your favorite virtual hosting provider? I'm looking for your thoughts on SliceHost, Dreamhost VPS, Linode, 1and1 VPS, etc and why you like the particular provider you named. Thanks!
15
votes
7answers
6k views

du vs. df difference

I have a fileserver where df reports 94% of / full. But according to du, much less is used: # df -h / Filesystem Size Used Avail Use% Mounted on /dev/sda3 270G 240G 17G ...
9
votes
2answers
2k views

Sharing Domain name between domain controller and webserver

In our network the name of the network domain is also the domain of the organisation's website (say, example.com). Externally people can enter example.com to visit our website but internally this ...
6
votes
2answers
1k views

Installing a third party application package on CentOS 6.4 fails due to missing dependencies libcrypto.so.10 and libssl.so.10

This is a Canonical Question about OpenSSL binary compatibility issues between Red Hat Enterprise Linux (and its derivatives) 6.4 and 6.5. This issue applies to a wide variety of third party ...
2
votes
4answers
4k views

How can I stop a currently active DDoS attack? [duplicate]

My VPS is under a DDoS attack. I cannot access RDP, and I cannot take it offline, or access it in any way at all. What can I do? They are not trying to bruteforce, just trying to stop access to the ...
50
votes
9answers
11k views

Company Password Management [closed]

The topic of personal password management has been covered in great detail time after time. This question is aimed at the business or organization that needs to keep track of many unique passwords for ...
103
votes
5answers
9k views

Are SSD drives as reliable as mechanical drives (2013)?

SSD drives have been around for several years now. But the issue of reliability still comes up. I guess this is a follow up from this question posted 4 years ago, and last updated in 2011. It's now ...
19
votes
3answers
13k views

Linux - How can I see what's waiting for disk IO

I have a server that has a really high load. Nothing is jumping out at me in terms of CPU usage, and it's not swapping. I think it's cause some processes are waiting for disk IO, and I want to see ...
62
votes
14answers
3k 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 ...
7
votes
13answers
21k views

HP Proliant DL380 G4 - Can this server still perform in 2011?

Can the HP Proliant DL380 G4 series server still perform at high a quality in the 2011 IT world? This may sound like a weird question but we are a very small company whose primary business is NOT IT ...
3
votes
1answer
2k views

Openfiler iSCSI performance

Hoping someone can point me in the right direction with some iSCSI performance issues I'm having. I'm running Openfiler 2.99 on an older ProLiant DL360 G5. Dual Xeon processor, 6GB ECC RAM, Intel ...
3
votes
3answers
2k views

Permission denied in vhost document root

I'm having a problem setting up a vhost on Apache 2.4, using CentOS 6.3. This question seems to have been answered several times on this forum, but none of the solutions work for me. Basically, I ...
7
votes
1answer
3k views

In DNS can an IN NS point to a CNAME?

Is it allowed to have an NS record be a CNAME? E.g.: subdomain.example.com. IN NS ns1.example.com. ns1.example.com. CNAME foo.example.com. foo.example.com. IN A ...
2
votes
2answers
2k views

Non-volatile cache RAID controllers: what kind of protection is there against NVCACHE failure?

The battery back-up (BBU) model: admin enables write-back cache with BBU writes are cached to the RAID controller's RAM (major performance benefit) the battery saves uncommitted and cached data in ...
45
votes
2answers
24k 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 ...
41
votes
17answers
18k views

Switching to IPv6 implies dropping NAT. Is that a good thing?

This is a Canonical Question about IPv6 and NAT Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How can I 'dip my toes' into dynamic IPv6 ...
30
votes
4answers
2k views

Why does DNS work the way it does?

This is a Canonical Question about DNS (Domain Name Service). If my understanding of the DNS system is correct, the .com registry holds a table that maps domains (www.example.com) to DNS servers. ...
49
votes
20answers
18k views

Hosting your own DNS

I currently have my ISP providing DNS for my domain, but they impose limitations on adding records. Therefore, I am thinking about running my own DNS. Do you prefer to host your own DNS, or is it ...
28
votes
2answers
15k views

How can I connect to a Windows server using a Command Line Interface? (CLI)

Especially with the option to install Server Core in Server 2008 and above, connecting to Windows servers over a CLI is increasingly useful ability, if not one that's very widespread amongst Windows ...
34
votes
4answers
85k views

How can I port forward with iptables?

I want connections coming in on ppp0 on port 8001 to route 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 ...
27
votes
7answers
13k views

What is “anycast” and how is it helpful?

I'd never heard of anycast until a few seconds ago when I read this SF post. The wikipedia entry on it is quite formal and doesn't really evoke a mental picture of how it would be used. Can someone ...
52
votes
13answers
22k 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 whats the difference between redundancy and a ...
21
votes
6answers
8k views

CIDR for Dummies

I understand what CIDR is, and what it is used for, but I still can't figure out how to calculate it in my head. Can someone give a "for dummies" type explanation with examples?
38
votes
12answers
1k views

Sell partitioning to me

I have often wondered why there is such a passion for partitioning drives, especially on Unixy OSes (/usr, /var, et al). This does not seem to be a common theme with Windows installations. It seems ...
18
votes
5answers
56k views

Finding why a user is locked out in Active Directory

A user's account keeps getting locked out in Active Directory. It's probably caused by an app that's using Windows authentication to connect to SQL Server. Is there a way to find out which app is ...
20
votes
6answers
26k views

Choosing local versus public domain name for Active Directory [duplicate]

What are the pros and cons of choosing a local domain name such as mycompany.local versus a publicly registered domain name such as mycompany.com (assuming that your org has registered the public ...
19
votes
5answers
14k views

How do I differentiate “fake RAID” from real RAID?

The Ubuntu wiki page on FakeRaid says the following: [A] number of hardware products ... claim to be IDE or SATA RAID controllers... Virtually none of these are true hardware RAID ...
17
votes
5answers
11k views

How can I chroot ssh connections?

I would like to setup a chroot jail for most (not all) users logging in though SSH. I've heard it's possible with the latest versions of openssh, but I've not been able to find out how to do it. The ...
16
votes
9answers
11k views

Multiple domains with SSL on same IP

I know that a dedicated IP is needed for setting up SSL. What happens if we add SSL for domains sharing an IP ? (Namevirtualhost)
14
votes
4answers
1k views

SSL certificate selection based on host-header: is it possible?

Is it possible for a web server to select an SSL certificate to use based on the host-header of the incoming connection, or is that information that is only available after the SSL connection is ...
255
votes
21answers
47k views

How do you search for backdoors from the previous IT person?

We all know it happens. A bitter old IT guy leaves a backdoor into the system and network in order to have fun with the new guys and show the company how bad things are without him. I've never ...
101
votes
12answers
95k views

How to set up Nginx as a caching reverse proxy?

I heard recently that Nginx has added caching to its reverse proxy feature. I looked around but couldn't find much info about it. I want to set up Nginx as a caching reverse proxy in front of ...
102
votes
25answers
179k views

Using DD for disk cloning

There's been a number of questions regarding disk cloning tools and dd has been suggested at least once. I've already considered using dd myself, mainly because ease of use, and that it's readily ...
126
votes
4answers
85k views

In Nginx, how can I rewrite all http requests to https while maintaining sub-domain?

I want to rewrite all http requests on my web server to be https requests, I started with the following: server { listen 80; location / { rewrite ^(.*) https://mysite.com$1 ...
73
votes
2answers
21k 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 ...
103
votes
9answers
85k views

What is a good SSH server to use on Windows? [closed]

In my spare time I remotely support my wife's office via VPN into a Windows Server. I am about to purchase a wireless broadband service which doesn't support VPN. I don't want to open up the remote ...
68
votes
19answers
13k 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 ...
43
votes
40answers
4k views

How do you manage your passwords?

Obviously seeing as how many of us here are system administrator type people, we have a lot of passwords strung out across numerous systems and accounts. Some of them are low priority, others could ...

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