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Top 15 vps interview questions

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Linode Distro (How to Choose?) 64bit? [closed]

I have made the leap to Linode (360MB) and wanted to get some feedback on which distribution to choose. I'm going to be running LAMP (with P being PHP).

I am mainly curious about security, performance, stability and future patching.
Should I go with a 64bit version of the OS or are there drawbacks with that?

Choices ...

Arch Linux 2009.02
Arch Linux 2009.02 64bit
CentOS 5.3
CentOS 5.3 64bit
Debian 5.0
Debian 5.0 64bit
Fedora 11
Gentoo 2008.0
Gentoo 2008.0 64bit
OpenSUSE 11.0
Slackware 12.2
Ubuntu 8.04 LTS
Ubuntu 8.04 LTS 64bit
Ubuntu 9.10
Ubuntu 9.10 64bit


Source: (StackOverflow)

Optimizing Apache and MySQL on Linux Xen VPS

I have a Xen virtual private server (VPS) running Ubuntu 8.10, with 128M RAM.

I've found several "how to optimize Apache and MySQL for low-memory VPS" pages via Google, but they provide contradictory information. So I'm asking Server Fault: how does one optimize Apache and MySQL for a low-memory VPS configuration?

A couple of people have suggested using nginx instead of Apache. I'll look into that, but I'd prefer to stick with Apache if possible, just to avoid having to learn all about configuring application stacks on top of an unfamiliar (to me) web server.

Source: (StackOverflow)

Automating server deployment

I find i am constantly settings up pretty much nearly identical servers and VPSs for a number of my clients and it can be very time consuming. Often the only thing that changes between each deployment is the different website that is to be served. Is there an easy way to automate all this and take the boring monotony of setting up 56 identical servers?

The servers i have deployed so far have only been Ubuntu, but it may be possible that i start to use other linux OSs or even Windows. So far i have looked at Capistrano, but it seems to be focused on writing little ruby programs to do the job with, and i have no knowledge at all

Source: (StackOverflow)

Why is my bare-metal 16x 2.93GHz cores computer performing poorer than a VPS with 4x 2.5GHz cores?

I have a written a piece of multi-threaded software that does a bunch of simulations a day. This is a very CPU-intensive task, and I have been running this program on cloud services, usually on configurations like 1GB per core.

I am running CentOS 6.7, and /proc/cpuinfo gives me that my four VPS cores are 2.5GHz.

processor       : 3
vendor_id       : GenuineIntel
cpu family      : 6
model           : 63
model name      : Intel(R) Xeon(R) CPU E5-2680 v3 @ 2.50GHz
stepping        : 2
microcode       : 1
cpu MHz         : 2499.992
cache size      : 30720 KB
physical id     : 3
siblings        : 1
core id         : 0
cpu cores       : 1
apicid          : 3
initial apicid  : 3
fpu             : yes
fpu_exception   : yes
cpuid level     : 13
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon rep_good unfair_spinlock pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm arat xsaveopt fsgsbase bmi1 avx2 smep bmi2 erms invpcid
bogomips        : 4999.98
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

With a rise of exchange rates, my VPS started to be more expensive, and I have came to a "great deal" on used bare-metal servers.

I purchased four HP DL580 G5, with four Intel Xeon X7350s each. Basically, each machine has 16x 2.93GHz cores and 16GB, to keep things like my VPS cloud.

processor       : 15
vendor_id       : GenuineIntel
cpu family      : 6
model           : 15
model name      : Intel(R) Xeon(R) CPU           X7350 @ 2.93GHz
stepping        : 11
microcode       : 187
cpu MHz         : 1600.002
cache size      : 4096 KB
physical id     : 6
siblings        : 4
core id         : 3
cpu cores       : 4
apicid          : 27
initial apicid  : 27
fpu             : yes
fpu_exception   : yes
cpuid level     : 10
wp              : yes
flags           : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall lm constant_tsc arch_perfmon pebs bts rep_good aperfmperf pni dtes64 monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca lahf_lm dts tpr_shadow vnmi flexpriority
bogomips        : 5866.96
clflush size    : 64
cache_alignment : 64
address sizes   : 40 bits physical, 48 bits virtual
power management:

Essentially it seemed a great deal, as I could stop using VPS's to perform these batch works. Now it is the weird stuff...

  1. On the VPS's I have been running 1.25 thread per core, just like I have been doing on the bare metal. (The extra 0.25 thread is to compensate idle time caused by network use.)
  2. On my VPS, using in total 44x 2.5GHz cores, I get nearly 900 simulations per minute.
  3. On my DL580, using in total 64x 2.93GHz cores, I am only getting 300 simulations per minute.

I understand the DL580 has an older processor. But if I am running one thread per core, and the bare metal server has a faster core, why is it performing poorer than my VPS?

I have no memory swap happening in any of the servers.

TOP says my processors are running at 100%. I get an average load of 18 (5 on VPS).

Is this going to be this way, or am I missing something?

Running lscpu gives me 1.6GHz on my bare metal server. This was seen on the /proc/cpuinfo as well.

Is this information correct, or is it linked to some incorrect power management?

[BARE METAL] $ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                16
On-line CPU(s) list:   0-15
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             4
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 15
Stepping:              11
**CPU MHz:               1600.002**
BogoMIPS:              5984.30
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              4096K
NUMA node0 CPU(s):     0-15

[VPS] $ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    1
Socket(s):             4
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 63
Stepping:              2
**CPU MHz:               2499.992**
BogoMIPS:              4999.98
Hypervisor vendor:     KVM
Virtualization type:   full
L1d cache:             32K
L1i cache:             32K
L2 cache:              256K
L3 cache:              30720K
NUMA node0 CPU(s):     0-3

Source: (StackOverflow)

Uses for a small Virtual Private Server?

I rented a small VPS (~130MB of RAM) to run an IRC bot. The bot is no longer needed so I have a VPS until the billing period ends.

I also have shared web hosting but can anyone think of what a VPS might be useful for that can't be done on shared hosting?

I'm a developer for both web and desktop apps.

Suggestions for larger VPS's also welcome.

Source: (StackOverflow)

Are vCPU the same as 1 Socket, or a single Core?

Currently I have a Hyper-v VPS with 2 (vCPU) processor. I would like to install SQL Server Express 2012 that has a limitation of 1 Socket or 4 Cores, whichever the lesser.

My Question: Are vCPU's counted as a single core, or as sockets? or something completely different?

Source: (StackOverflow)

How do I install CoreOS on Linode? [closed]

I'm trying to install CoreOS on my linode server, I followed the guide for installing custom linux distributions here: https://library.linode.com/custom-instances/custom-distro-howto#sph_creating-the-virtual-machine

However in step 16 it says to select the image of linux distribution. I can't seem to find a CoreOS image for the same.

I then tried to connect to my node using LISH in rescue mode and then install directly to the /dev/xvda path using the coreos install script mentioned here: https://coreos.com/docs/running-coreos/bare-metal/installing-to-disk/

It showed successfully installed but then when I tried to reboot my linode it din't boot up.

Have I done it right ? or is there something more I must do to make it work on Linode ?

Source: (StackOverflow)

Removing Apache from Debian 5

I had Debian 5 installed on my VPS but I found that it came with apache2 already up and running. I tried

apt-get remove apache2

but it said that apache2 wasn't running. I checked top and yep, there it was. So then I turned it off.

/etc/init.d/apache2 stop

which worked fine and shut the daemon down. However, I still can't remove it. I tried aptitude remove but it says that it isn't installed.

What is going on?

Source: (StackOverflow)

Is there tool that will monitor or log speed of web server responses [closed]

I have GNU/linux Box (linode VPS running Debian) with PHP, Apache, MySQL and Varnish (and app/site that use those) is there a tool that will save or monitor load times of web server responses?

Source: (StackOverflow)

VPS Administration for the Absolute Beginner

I have a new site that I want to build, something that I as a programmer wish existed. While there is no way this site would ever reach StackOverflow levels of success, I do hope that it will have a broad appeal and become decently successful - I'm optimistic, anyway.

I'm going to start with a shared host, possibly sticking with the company which hosts my blog since I know them well enough, but I don't think shared hosting is a good long term solution.

As such, I've been checking out various VPS providers, mainly Slicehost and Linode so far, for their potential as a "next-stage" provider. The problem is that I feel I would be completely out of my element with a VPS. I only have limited experience with Linux (I've tried it a few times on my laptop, but always ran into issues that made me give up on it - usually wireless issues), and while I'm pretty sure I could get the basics setup, I worry that I'd leave things horribly insecure or that I just couldn't handle maintenance issues.

Obviously, my idea may flop entirely, but I'd rather not get caught with my pants down if I ever got to the stage where a VPS becomes a necessity.

So, are there any good tutorials / (e-)books / articles describing how to get to know your VPS, or any other issues I should be concerned with. The site would most likely be a "classic" LAMP stack, though I may decide to swap things out later on as the need (or want, really) arises.

My absolute top priority in this is security, hence this post. I have very little doubt, given the resources online - most notably Slicehost and Linodes tutorials sections, that I could hack together a workable solution, but I need to know that I'm not leaving critical vulnerabilities open by doing this.

An ounce of prevention, etc.



I've also asked this question at Hacker News and Reddit over the past couple of days, so perhaps the links to those discussions might be useful:

Source: (StackOverflow)

My server Admin wants me to set public write permissions on a directory

I'm relatively new to web development, so please be patient.

I'm primarily an iPhone developer, but have recently done a site for someone else using shared hosting. I could write to files in PHP on that site fine, without having to think about permissions.

I'm in the process of deploying a web service for a new app I'm making, but it's not really going smoothly. The most important difference here is I'm using someone else's server, and just have FTP/DB access.

Basically, I have a load of PHP files which make up my CMS, like so:


Those scripts then either edit the database, or files. They can interact with the DB fine, however, my scripts cannot write to the filesystem. They might, for example, attempt to write to the following files:


This worked fine on my MAMP install (locally), but once deployed to the server, PHP spewed out errors everytime a write was attempted... something like this:

Could not open file "../data/img/someimage.png" for writing.

So I emailed the guy who's running the server, and he came back saying:

Does it work with public permission? (777)

And, it did - but I was very cautious with using public permissions, so disabled it straight away again. I emailed him saying "how can I make my PHP scripts write using standard user permissions", and he said:

Leave it as public, it'll be fine

I reckon it's an ip conflict somewhere in the domain resolution, but I'm not worried about it.

I then emailed him saying "surely this is insecure" or something along those lines, and he replied with the following:

the reality is that there are millions of website, including several that I manage that have 777 on various folders, it's just a way of life.

Could anyone give me some idea of a solution I could give him? Or what I can do to avoid having to use 777? I really don't like the idea of any folders on my site/service to be publicly writeable.

I would very much appreciate your advice as I know very little about web servers.

Source: (StackOverflow)

Which virtualization platforms should I choose, Xen or OpenVZ? [closed]

I am upgrading my shared hosting to VPS hosting, mainly to just add server administration skills to my development skills, so I'm facing a lot of new choices just signing up.

I need to choose a virtualization platform, either Xen or OpenVZ.

From what I can tell, OpenVZ is more "user-friendly", but other than that I can't really tell a difference.

I'm going to choose Ubuntu Linux, just because I believe it is the most user friendly and very popular, and I assume both Xen and OpenVZ work equally well with it.

For my purposes of "learning how to administrate a server" which do you think would be more appropriate, Xen or OpenVZ?

Source: (StackOverflow)

Renting a dedicated, but getting a VPS. How to detect? [duplicate]

This question already has an answer here:

When renting a dedicated server, how can one be certain than he/she is not getting a VPS or some other virtual machine variant instead of a true dedicated hardware box?

Which checks can be run (assuming it is a linux box) to detect such case?

Source: (StackOverflow)

Why does `df` indicate no available space when used is much less than total size, on my VPS? [duplicate]

This question already has an answer here:

My VPS display this with df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/simfs      100G   46G     0 100% /

Does anyone have a idea to fix this ?

Source: (StackOverflow)

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.


Source: (StackOverflow)