I have an HP ML350 Gen 8 server with 8 SAS HDDs of 600 GB each. Since the drives are a little bit old now, I would like to replace them with SSDs.
I would like to know if I can do this, and if I should continue the existing RAID setup.
I was wondering if anyone had any knowledge on how this idea can be done. It's not a requirement but more of an idea I came up with that I don't know how to word my google searches to find out if it's been done.
Basically the idea is this. I have an Ubuntu Postfix/Dovecot mail server with Amavis, Postgrey, and Spamassassin. Now I've heard of using Sieve for dovecots spam folders and such. But I'm wondering if there's a way to enable users to forward an email to a spam address, such as spam@example.com, that will basically act as a robot user and file the email away in a kind of universal junk folder and automatically add that address to spamassassin or postgrey. Eventually I would like to have it also clean out the folder ever X amount of days (probably with cron).
So the work flow I'm hoping would go as such:
Ideas? If I can get this working I might write up a tutorial on it for others if one doesn't allready exist.
Answer
Forwarding spam often isn't really that helpful, users usually do "inline forwards" instead of redirects / forward as attachment. it's almost impossible to get any usable information out of inline forwards (no headers, which means no envelope sender etc).
Fortunately, dovecot has a much cooler feature: you can search through a folder in all user accounts at once, so instead of forwarding they can simply move the false negative to their own Spamreport folder.
You can then do funny things with doveadm, for example:
doveadm search -A mailbox Spamreport 2>/dev/null | while read user guid uid; do doveadm fetch -u $user text mailbox-guid $guid uid $uid | your_blacklist_script_here.sh ; doveadm expunge -u $user mailbox-guid $guid uid $uid ; done
this would get all messages that are in a folder called Spamreport in any user account, pass them to your_blacklist_script_here.sh and expunge them afterwards.
Note, your idea of blacklisting sender adresses might work in some cases, but usually they change very fast, so it probably wont be very effective.
Consider training the spamassassin bayes database instead. Assuming you have bayes set up, simply replace your_blacklist_script_here.sh with sa-learn --spam
I've found most website attacked by mass DDoS has spike increase in alexa rank.
But how about the position in search engine?
I want to know is there a way to make a snapshot-like backup of a linux system into a single file and restore it in another system ?
You know in windows there are programs which makes a copy of a drive (like C:\ ) into a single image file. So you can restore this file later incase you are infected or something happens.
Every time I want to migrate my vps into another host, I have to setup the new server from scratch and move the files manually. Can I just make a snapshot backup of the whole system and restore it somewhere else (or on the same server) ?
I am not familiar with linux and I have no idea if this is technically possible or not ? Does the paritions, configs, system files,etc... are individual for each system ?
I heard about rsync, but that's not what I am looking for.
Answer
While snapshot style backups are possible in some situations, they will not be useful in this situation. The main reason for this is that VPS providers rarely give you low enough level access to their system for you to be able to restore data in this fashion.
The real answer here is to use a config management system to manage your servers. Puppet and Chef are two of the most popular configuration management systems at the moment. With systems line these, you specify in a set of text files how you'd like your server to be configured, what packages you want installed, etc. These configurations then can be applied to any server, regardless of its location.
I am trying to understand how massive sites like Facebook or Wikipedia work, for my intellectual curiosity. I read about various techniques for building scalable sites, but I am still puzzled about one particular detail.
The part that confuses me is that ultimately, the DNS will map the entire domain to a single IP address, or a handful of IP addresses in the case of round-robin DNS.
For example, wikipedia.org has only one type-A DNS record. So, people from all over the world visiting Wikipedia have to send a request to the one IP address specified in DNS.
What is the piece of hardware that listens on the IP address for a massive site, and how can it possibly handle all the load coming from the requests for users all over the world?
Edit 1: Thanks for all the responses! Anycast seems like a feasible answer... Does anyone know of a way to check whether a particular IP address is anycast-routed, so that I could verify that this really is the trick used in practice by large sites?
Edit 2: After more reading on the topic, it appears that anycast is not typically used for dynamic web content. Anycast is usually used for UDP (e.g., DNS lookups), or sometimes for static content.
One interesting thing to note is that Facebook uses profile.ak.fbcdn.net to host static content like style sheets and javascript libraries. Each time I ping this name, I get a response from a different IP address. However, I can't tell whether this is anycast in action, or a completely different technique.
Back to my original question: as far as I can tell, even a large site will have a single expensive piece of load-balancing hardware listening on its handful of public IP addresses.
Answer
It isn't necessarily a piece of hardware doing this but a complete system that has been designed to scale. This not only encompasses the hardware but more importantly the application design, database design (relational or otherwise), networking, storage and how they all fit together.
A good starting point for your curiosity on finding out how some of the large sites scale is High Scalability - Start Here and High Scalability on Wikimedia architecture, Facebook and Twitter as examples.
Regarding your question about DNS and single IP addresses and round-robin these types of sites will often use load balancing as a method of presenting a single IP address. This can be done either by specialised hardware load balancers or through software running on general purpose servers. The incoming requests to the IP managed by the load balancer is then distributed across a series of servers transparently to the end user.
For a good explanation on this topic, including a comparison of hardware and software load balancers/proxies and how they compare to DNS round robin, have a read of Load Balancing Web Applications.
I need to rewrite URLs like
http://www.domain.com/blog/wp-content/uploads/this-is-a-static-file.jpg
to
http://www.domain.com/wp-content/uploads/this-is-a-static-file.jpg
I am using this rule:
location /blog/wp-content$ {
rewrite ^/blog/wp-content/(.*)$ /wp-content$1 last;
}
The weird thing is that only URLs directly behind wp-content and without static files are rewritten correctly:
http://www.domain.com/blog/wp-content/uploads/ => http://www.migayopruebas.com/wp-content/uploads/
However, it there are more than one sub level OR a static file is involved, it doesn't work:
http://www.domain.com/blog/wp-content/uploads/migayo-trangulacion-laton.jpg => doesn't change
http://www.domain.com/blog/wp-content/migayo-trangulacion-laton.jpg => doesn't change
Could anyone point me out to the right way to do this? I've been read Nginx doc and several examples and still can't make it work.
Thanks a lot, regards.
Answer
Your solution doesn't work, because you don't have a regex location (the ~ character is missing), and you end the location with the $, which is a regex character.
You can do it in a bit simpler way:
location ~ /blog/wp-content/(?.+)$ {
rewrite ^ /wp-content/$filename last;
}
So, here you do the regex capture in the location directive, and use the captured part of the path with the rewrite destination.
If you want to make a client side 301 redirect, use the following:
location ~ /blog/wp-content/(?.+)$ {
rewrite ^ http://www.domain.com/wp-content/$filename permanent;
}
We have IIS7 on windows 2008 and we installed verisign certificate and bound it to https. Certificate seems fine.
Chain:
mysite.com - not expired
VeriSign international server CA class 3 - not expired
Verisign Class 3 Public primary certification Authority - not expired
Yet when I use verisign online validation, I get that second certificate is expired.
https://knowledge.verisign.com/support/ssl-certificates-support/index?page=content&id=AR1130#
This is what it reports, mysite is reported to be ok:
--Issued To--
Organization: VeriSign Trust Network
Organizational Unit: www.verisign.com/CPS Incorp.by Ref. LIABILITY LTD.(c)97 VeriSign
Organizational Unit 2: VeriSign International Server CA - Class 3
Organizational Unit 3: VeriSign,, Inc.
--Issued By--
Organization: VeriSign,, Inc.
Organizational Unit: Class 3 Public Primary Certification Authority
Country: US
Validity Start: Wed Apr 16 17:00:00 PDT 1997
Validity End: Wed Jan 07 15:59:59 PST 2004
Any ideas?
Answer
Did you use the right intermediate and is it chained properly? VeriSign certificates are extremely picky.
I'd suggest trying the following:
1) Use VeriSign's site to lookup the common name for the cert: https://securitycenter.verisign.com/celp/enroll/outsideSearch?application_locale=VRSN_US&originator=VeriSign:CELP
2) Cross-reference the name in the search with the required intermediate here: https://knowledge.verisign.com/support/ssl-certificates-support/index?page=content&id=SO11501&actp=search&viewlocale=en_US&searchid=1275755447299
3) Examine the certificate bundle you received and ensure that the certs match up. You can use OpenSSL, keytool, Windows etc... whatever tools you have available.
4) Ensure that the root certificate exists on the server Windows will usually already have them updated.
Cheers,
-M