This topic plagues me to death every time I need to do some administrative function MySQL simply because I don’t do it every day.  I have 3 servers that I manage entirely via the command line now and all 3 require me to know at least some MySQL.  Unfortunately, I always end up going to several sources to get all the information I need.  So instead of doing that in the future, I’m writing this blog as a centralized reference for everything I need.  Hopefully you can use this blog as much as I will!

Note: You will need to click the “show code” icon in the top right corner to view the code entirely for some of the blocks that are longer than the code box.

POST UPDATED 6/5/2011 (deleting a user / listing users)

A few side notes:

1. Hosts: Mysql allows access to certain hosts.  % means allow the user to connect from any computer on the internet that can reach the database server, localhost / 127.0.0.1 both will allow the user to connect only from the local database server.
2. means you need need to put in the appropriate information

Basic User Commands:

mysql -u <username> -p

• Login may require -h
• This is done through SSH / the console, not within the MySQL interpreter!

update mysql.user set password=PASSWORD("<new password>") where User='<username>';

• You don’t want to use % or other mysql special characters in the password as they will cause you grief when using other commands.
• This should be done within the MySQL Interpreter

Backup / Restore Commands:

These should be done through SSH / the console!  NOT within MySQL’s interpreter!!!

mysqldump -u root -p'<mysql root's password>' --all-databases > <filename>.sql

mysql -u root -p<Root's Password> < <filename to restore backup with .sql extension>

mysqldump --user=<username> --password=<password> --databases <database> --opt --quote-names --allow-keywords --complete-insert > <filename>.sql

mysql -u <username> -p<User's Password> < <filename>.sql

General Administration Commands:

NOTE: All of these commands should be done within the MySQL interpreter!

create database <database name>;

drop database <database name>;

create user '<username>'@'<allowed hosts>' identified by '<user's password>';

grant all on <database name>.* to '<username>'@'<allowed hosts>';

select host, user, password from mysql.user;

delete from mysql.user where user='<username>';
delete from mysql.db where user='<username>';

flush privileges;

exit;

update mysql.user set host=’<allowed hosts>’ where user=’<username>’;

update mysql.db set Host='<allowed host>' where Db='<database name>';

update mysql.db set Host='<allowed host>' where  Db='<database name>';

use <database name>;

show databases;

show tables;

describe <table name>;

Disclaimer:

I may have got a few of these commands incorrect (typo).  If I did, please let me know so I can fix them asap.  If I missed a command that you’d like, please comment and I will add it.

Over the past week, I got a new server to host Microsoft Exchange which is a powerful email server from Microsoft.  Before you go all crazy on Microsoft (I know I typically do), Exchange is one of the few excellent products they make.  I am actually very hard pressed to find anything that compares to it that is open source and can easily run on Linux which 99% of  my hosting business up until now has ran off from.  Man, I never thought that I would say that

So the first logical question is, why move your email to exchange?  As you know, I’ve had 1and1 mailxchange now for quite some time.  I really wanted a solution that would sync my calendar, contacts, tasks, files, and email to every device I use on a daily basis.  Mailxchange was that solution but there are many problems. First the web client is very slow,  sure its flashy, but it takes 5 minutes to load on my connection (that is fairly fast).  I don’t have the time to wait on this client to load.  The next problem is it needs custom software to connect to Outlook and Mobile Devices, I’m not into installing “connectors” to software when it has functionality built in with other products.  Perhaps one of my biggest problems is the level of support I’ve gotten from 1and1.  My mail has gone down on a few occasions and I’ve been unable to easily send a support ticket in asking what is wrong.  I’m not even sure if 1and1 backs up my email and I have no method of backup, so I’m kind of stuck if they go down or don’t back up the server.  Its kind of scary actually since I save all of my email.

So about 2 weeks ago, I started talking to a few friends.  I know that I get a free msdn copy of Microsoft Exchange 2003 and Server 2003 from my University.  I figured if I could find a few friends who were interested in small mailboxes on exchange, I could cover the cost for the hardware to host my copies of this software.  I figured that I could host 4 people and handle a server that costs $25 a month from 3dgwebhosting which I’ve had in the past and they run excellent hosting on Windows server 2003.  They cover the license cost, so I’d only be covering exchange.  The downfall was I would only have 10GB to work with which isn’t a lot for email and backups.  Because of this, I looked for alternate hosting.  I decided that if I could find xen hosting, xen would support Windows.

About this time when I was looking, I knew that http://fsckvps.com who is a child company of vaserv in England hosted xen vps machines.  I went to that site to look up their support email and found out about the horrible hypervm owner hanging and they were down.  Anxious to get this hosting off the ground, I began looking at alternate places for hosting.  Shortly after, I found good reviews on other blogs of a new hosting company called Elite Data Hosting.  I contacted them about a 10mbps plan to host exchange on and they got an account for me on a xen vps using my server key.  I’m basically paying $15 a month for ~325MB of ram and 30GB of hard disk space.  The server is a high end server and I have had no complaints.  They even took the time to install Windows for me from my disk!

Elite Data Hosting is good news for me because I now can have my 2 guaranteed friends and myself have a guaranteed 5GB of space for files / mailboxes a piece.  It will also be very easy to automate backups of these mailboxes.  We all split the $5 a month cost for the server so I’m basically paying what I would be paying 1and1 but I control my backups and have a better piece of mind.

So now I started the daunting task of setting up the Exchange server. Normally with Microsoft products, it takes about 5 seconds and about 10 clicks of the next button to install software and another 3 minutes to say configure this software to do this.  By that point, everything normally works flawlessly (except for the occasional crashes of Microsoft Windows).  On linux, there is always a lot of configuration, but linux always works without the crashes and instability.  Perhaps this is the way to tell what is good and bad???

To get back to Exchange, I must say, this is the hardest piece of software I have ever had to install on both Linux and Windows.  Part of the reason is the way Exchange relies on existing Server 2003 infustructure to improve itself.  I’m not so sure if I’d rely on a Windows Server operating system, but I really have no choice with Exchange.  Exchange requires Active Directory among other server features to run correctly and the prerequisite list is a nightmare to get through in less than 5 hours if you ask me.  I started with a clean server a week from last Tuesday and didn’t get Exchange running until about Monday and I had 8 hours a day into it at the very least.  I will take part of the blame for not knowing what I was doing past Active Directory configuration, but Exchange was no day at the beach to figure out.  I also had a lot of errors that I spent hours reading about to find simple fixes.  Finally after all of the struggle, I got exchange fully working to the point where I wanted it about 2 days ago. During my struggle, I posted a lot about my solutions on Admin Reference which is my site where I post solutions to all of my problems.  I picture it as another *free* experts exchange but more tutorial based than question based.  Maybe some day it will do a little of both   That is my goal anyways!

One side note that I should add is, when I first loaded Outlook Web Access, I got a crappy looking interface.  I found out quickly that Exchange only supports Internet Explorer in its premium interface (the one that looks nice and loads quick).  Sadly, this is the only reason why I have opened Internet Explorer, and I have found that Firefox can open an IE tab, so I’ve began using that.  I will also likely find a solution when I migrate completely to Linux (my next upcoming project).

So now that Exchange works, what was so difficult? Most of my difficulty was from I never managed an exchange server in the past, and I couldn’t find any decent documentation on how to do it. That is why I posted a lot to Admin Reference unlike I normally would.  My biggest issue was the domain errors which were caused by firewalls and figuring out how to get Outlook Web Access and Outlook Mobile Access working with SSL encryption.  I also was not prepared to spend money on an SSL certificate (required by exchange) and provide antivirus / spam scanning to the server.  I was under the impression that spam/virus protection was built in, but it isn’t, and the freeware gfi version is no longer free.  I figured out how to migrate linux spamassassin to the server and that is adequate for spam protection

One last question that I should cover is why didn’t I go with Exchange 2007?  I will admit that Exchange 2007 is very nice software, but there are a few problems:

• My first issue would be, Exchange 2007 is really bloated.  If you compare the 2003 to 2007 installation disks, the 2003 install disk is about 300MB, the 2007 version is closer to 1.7GB.  That is a huge difference, one that I’m not willing to upgrade for.
• My next issue is due to the bloat, I would need a much powerful server.  I could upgrade to the 600MB RAM server plan with a 50GB hard disk or so for 30 dollars a month, but then I would have to start hosting more mailboxes than I’d want to to cover the costs, and I’m not really into that idea.  I might upgrade for 2003 if people are interested and it won’t take too many server resources or hurt my rigged spam fighting solution, but that is a decision that I’d rather not make now since it works perfectly as is!
• My final issue is, newer software normally sucks.  I always wait for at least Service Pack 1 (2 if possible) until I start using a product mainstream.  Exchange 2003 is at SP2 while Exchange 2007 is at SP1.  With other Microsoft software, I’ve found that when I compare a fresh install of Server 2003 to Server 2008: Microsoft Server 2003 with a GUI (Graphical User Interface or your windows desktop) uses 400MB on a new install, while the Microsoft Server 2008 Core Edition (no desktop, strictly command line to reduce bloat) uses 800MB on a new install with nothing configured.  This is a huge jump and I have a feeling that Exchange 2003-2007 will be very similar (the requirements for 2003 is 256MB of ram, 2007: 2GB of ram).  BIG DIFFERENCE, huh!

All in all, I figure I am paying about $200 bucks total for my new email solution, but my friends really do help cut the cost down to where I can happily afford it.  I still have 1 slot open but have a feeling that will be closed before long.  For a private email server, I consider it an excellent learning experience, and a good way to get some good content on Admin Reference! Hopefully you got some helpful tips out of this.

One final note:  I’d like to put a plug out there to any other system admins.  If you are like me, you are always running into new problems that don’t have easy solutions.  Why not take a few minutes when you find the answer and post it to Admin Reference?  Maybe someday you will look back on it (I know I have) and say thats how to fix it!  Someday when it gets a little more material, I plan on integrating the forum into a wiki that is easily searachable for solutions to problems.

Prior to last October (2008), I have solved a wide array of problems consisting of Apache malfunctions and complete Server Hard Drive failures requiring data recovery, to simply having to unblock a person’s ip address from the firewall because they tried to login to the server incorrectly too many times.  I never really messed a server up so badly that I couldn’t undo what I attempted to fix in the first place.

The biggest problem that I have ever had up until October 2008 was with an email server’s outgoing email queue.  All email that was sent from this server would always be refused by other popular mail servers on the internet due to it not having the correct configuration.  I never did figure out that error, and instead I changed the software that manages the email server from LXAdmin to CPanel.  This fixed the problem, I never did understand why the server wouldn’t send, but CPanel fixed my mail problems and so many other problems that I sort of fixed on LXAdmin but didn’t really have a long term solution for.

Now that I have blabbed on enough about my experience, lets get to this blunder (I’m sure I’ve posted about it elsewhere, but I don’t recall putting it here).  In October, Justin, a good friend who runs AmpHosted came to me (this wasn’t the first time incase you are wondering) asking about some sort of tiny problem that he was somewhat unsure of how to fix, but he had the right idea and I confirmed it.  He also asked me how to free up space on the linux /var directory since his was getting pretty full.  I’m not sure how the conversation went anymore, however I know that there were a few possible solutions.

My first goal was to free up enough space so that the /var partition wouldn’t overflow and risk crashing the server.  Server crashes can be costly, and Justin was in no mood to lose money as a president of a strengthening hosting company.  So I began googling to figure out what log files were safe to delete.  I know that linux has a lot of log files that cannot be deleted safely, and I was finding these so I would know not to delete them.

My second goal was to have this partition expanded from free space on the other partitions so that the problem would have a more permanent solution (which did happen in November).

I then noticed that one of the mysql directories was using most of the space.  I quickly did a google search and read that it was safe to delete a mysql log directory.  Unfortunate for me, I only saw what I wanted to see, and didn’t read the article thoroughly.  Needless to say, I wiped out the /var/lib/mysql directory from his server, effectively freeing up a lot of disk space on the /var partition, and also wiping out the mysql server and all of the database files. On top of this, when I began looking for the backup files to quickly restore the databases within an hour, I found out quickly that some of the backups were corrupt and others non existant.  After restoring most of the server, one client lost a month of data and I felt horrible!

Since then, my admin buddies still push that blunder in my face.  I’m not entirely sure why because I still feel sorry for Justin.  I have also started taking the time to read what is safe to remove and not so I don’t accidently do something that bad again.  A mistake like that could have costed me my job or a pay cut if I was working directly for a big time hosting company, even if I did have 10 to 15 years of experience.

Since then, when it comes to matthouse and my own hosting company, or when I’m helping Justin, I always make sure to double check that I’m right before I proceed.  I know that I’m now slower, but I also have made changes to my procedures to make them more safe, sacraficing speed in my repairs.

I feel that I should write this blog for 2 reasons, 1. to make it known that I DO make mistakes and I’m not perfect, and also, I hope that anyone who reads this blog will make sure to check twice before doing an operation that is not reversable (at least easily).

I will be taking a system administration course next semester which is linux based with a FreeBSD pioneer teaching that course.   The final reason why I wrote this was to say how good of an Admin I consider myself now, so that after that course, I can re-rate myself and hopefully talk about a lot of my experiences in that class.

One final note, I’m still working on adminreference.com, and I will probably start posting more recent knowledge that I’ve acquired in the near future after this final week of college classes and work.

Earlier today, I helped a friend in the hosting business move a massive website (http://clevelandleader.com) from his server to a virtual server that will just host that website.  This website is ranked ~76,000 on the alexa scale which means that it gets an insane amount of traffic.  My best guess would be 300 to 1500 loads per second.  The site itself has a huge mysql database that is over 2GB and the sql move alone almost crashed a dedicated server with a quadcore processor (it did have a lot of other websites on it though).  Regardless, after the move, my friend didn’t realize that a default whm (cpanel, inc) installation doesn’t optimize the server nearly enough for a large website like this.  Heck, I don’t even know if whm was made for such a large website.  I did optimize the server and compile apache correctly just to handle the needs of clevelandleader.com.  I also did a lot to prevent apache from crashing with the high load.

Traditionally, with such a large website such as cleveland leader, the web server hosting the site would only run a web server, no overhead like cpanel.  I feel that cpanel has made the hosting process much easier, but I just don’t think it was made to handle such a large website.   Also, the fact that cpanel uses the root password directly means that if there is a security vulnerability and the user obtains that root password through hacking or whatever, the server could be compromised not only from cpanel’s whm but also from the terminal through ssh (or a rare occasion of console access, meaning sitting in front of the server physically).  This could present a major problem.  Most smart hosting companies use cpanel’s wheel group to give su access to certain cpanel uesrs that can then login to the terminal via ssh and then su root with the root password to gain root.  This provides a 2 password layer and adds an additional layer of security to the server.

Another pitfall that large websites face is the need for a dedicated mysql server, that is if mysql can even handle the load.  Mysql was made for small to medium sites and it was made for maybe 100 to 200 queries per second, but much more than that and it undergoes a massive strain.  Many large websites find themselves moving to more powerful database servers such as Microsoft SQL or Oracle which are much more powerful solutions that were made for high loads.

So why am I even talking about this!  I felt that this would be the best way to introduce a new idea that I’m going to begin working on within the next couple of weeks.  I have purchased the domain (http://adminreference.com) and will begin a forum where users can share their administration experience and knowledge to the world.  I am a seasoned Windows administrator and a somewhat experienced Linux admin.  I find myself knowledgable about both server operating systems and I post tutorials on multiple websites that don’t really aim for administration concepts.  I also hope that some day this can help me when I am stuck on a massive problem.

I encourage you to stay informed as I begin this new journey.  I will likely be ready to release the site sometime in the next couple of weeks.  I am not sure how to market such a website, however I’m sure as people begin coming, someone will have knowledge about that as well.