Last week I learned a valuable lesson about backing up MySQL, it was this:

• It is not enough to copy the files out of /var/lib/mysql or wherever if you want to backup your databases.

The thing with copying files is that if the mysql daemon is still running, there’s no guarantee that the physical files are up to date or even consistent. MySQL can do its own housekeeping whenever it would like to which means file write operations. It also keeps information in memory and will write it to disk at a later time to suit itself. The recommended backup method for MySQL is to use the mysqldump tool – more on that later.

The Scenario

Having had a server failure and discovered that file backups taken while the mysql server was running was all we had, I was unsure if we were going to get everything back. I did manage to recover the databases, by doing the following:

1. Find a server with a similar version of mysql. Happily my “lost” server was 5.0.21 and our development box runs 5.0.24 so I wasn’t too worried about changes in file formats.
2. Stop the mysqld on that box
3. Copy the files into /var/lib/mysql (this is on ubuntu but I think its a pretty similar setup on other distros). I didn’t have any data on this machine to start with which made things simpler. MyISAM stores its data in directories called the name of the database.
4. Check the file permissions – the files need to be owned by the user that mysql runs as. This caught me out the first time around.
5. Bring up mysqld and hold your breath.

In the event we seem to have most things and to be honest that’s more than I dared hope. There are some corrupt tables but nobody can swear that they weren’t like that before so with a bit of luck we won’t make any nasty discoveries further down the line [1].

MySQL Backup Strategy

I’ve been doing some setup on the new servers and backing up what was salvaged from the old one. I’ve devised a simple loop which dumps and zips each database in turn, using a shell script. The code for the script is below:

#!/bin/sh
for i in `mysql -B -u root -e “show databases” | tail -n +2`; do
echo $i
mysqldump -u root $i | gzip -9 > mysql/$i.`date —iso-8601`.gz
done

Its nothing that isn’t used by sysadmins everywhere but its simple and it works for me so its here (for when I forget what I did!). This example writes a .gz file for each database into a folder called mysql in the same location as where you call the script from. You probably also need to add -p switches to both the mysql and the mysqldump calls unless you are running with no root password which is rarely a good idea.

I hope this is all helpful to someone; I know I learned some useful lessons this week!

¹ I’d also like to point out that this was an internal server with little critical information on it and a backup routine that’s been running so long nobody can remember setting it up. Which isn’t great but its less bad that it might be.

I’ve been having fun over the last few weeks, writing about the fun things that you can do with Unix (see earlier articles about cowsay, fortune, mesg and go fish). This is the last in the mini series unless anyone has any other good suggestions for things that should belong here, and its MOTD or “Message of the Day”.

When you log into a unix box (or linux box, I’m using the term fairly indiscriminately in this instance) you will get a standard greeting message, usually telling you what kind of a system it is and adding a bit of a disclaimer. They aren’t very interesting messages but they are easy to change. Look at the contents of /etc/motd and you will see the text that gets displayed to a user on log in.

Traditionally this file is used by sysadmins to let users know of any changes that have happened or perhaps to warn of scheduled down time. However its also pretty usual to find something a bit more light-hearted there. My particular favourite is to add some ascii art as a welcoming banner to the user … what’s yours?

I’ve come across lorelle’s blog challenges before but this one caught my eye. The challenge is to come us with a search phrase that you are the top hit for in google. Here’s mine:

cowsay house

I think that pretty much sums up this whole site in fact! Can you rise to the same challenge? Let me know what your number-one-in-google phrase is.

Following on from the other articles in the fun with unix miniseries, today its go-fish. This is a game, from the package bsdgames and its addictive :) There are a bunch of other games in the package too but this has been a personal favourite for some years. Basically its a game of happy families, but with an ordinary pack of cards and text-only.

I installed the package on my ubuntu system with the command:

sudo aptitude install bsdgames

Run the game by typing

go-fish

Firstly you will be prompted to say whether you want instructions, then the game starts. You get a list of the cards you have, and you have to start asking for cards to make up “books” of four. Here’s a transcript of the beginning of a game:

Would you like instructions (y or n)? n
I get to start.
I ask you for: 5.
You say "GO FISH!"
Your hand is: 4 7 9 J J J K
You ask me for: j
I say "GO FISH!"
You drew Q.
I ask you for: 6.
You say "GO FISH!"
Your hand is: 4 7 9 J J J Q K
You ask me for: 9
I have 2 9's.
You get another guess!
Your hand is: 4 7 9 9 9 J J J Q K

When you make a set of four cards, it appears at the end of the list:

Your hand is: A A 6 7 7 10 10 10 Q K + Book of 3

The game ends when the cards run out and the winner is the one with the most complete “books”. Have fun!

Mantis is a rather good open source bugtracker. Recently I’ve been using it across a small team working on a number of projects at once, and its going pretty well so far. It is especially useful when someone is testing something and someone else is bug-fixing. Today I’ve been looking at some changes to the user setup and thought I’d jot some notes here in case someone else finds it useful.

Altering who is allowed to do what

By clicking on the “Manage” and then “Manage Configuration” and then “Workflow Thresholds” links in Mantis, it is possible to alter which roles have access to which features. The roles available are:

• viewer
• reporter
• updater
• developer
• manager
• administrator

Unfortunately, these role names can’t be changed – What I need is one for IT people, one for management and designers, one for contract IT staff and one for project management people. I’ve ended up writing an accompanying document saying which people should have which level of access.

From this page you can turn on and off most functionality for the various levels of user. You can set who can resolve or delete issues, change statuses, assign issues and so on – and also which levels can see the notes or a list of who is monitoring the issue. This probably makes more sense in a large organisation, or where different people might be doing different roles for different projects. As we’re quite a small outfit then quite a lot of people have administrator access and almost all other users have at least the role “developer”.

Changing what triggers email notifications

Mantis sends out WAY too much email for our liking – so under “Manage” and then “Manage Configuration”, look for the “Email Notifications” tab. Here you can alter the settings and if you have the defaults set, you’ll see that nearly everyone has them ticked to start with! Its a neat interface with options for people reporting bugs, people with bugs assigned to them, and people monitoring bugs too. There is also functionality to include people who have added notes to the bug or people of a certain threshhold who have been assigned to that project, but I’m not using those right now.

How the status flows

Also at this level of configuration is a screen called “Workflow Transitions”, which allows you to set default status for new issues, and then dictate which statuses can follow on from which other statuses and what the default next status is for each. I’ve seen this before in other applications and its very useful to give a hint to the user as to what should be happening next in the project process. I thoroughly recommend that if you are setting up mantis, or even doing some housekeeping on an existing installation, you spend some time thinking about how this screen could be set up to make things faster for users.

Am I making sense?

I hope this is useful to someone – if nothing else it will be an excellent aide memoire for me next time I want to fiddle with the settings! Let me know if this was helpful or if there’s anything I’ve missed.

The old ones are the best, so they say, and this is definitely the case with fortune. At the command line, type “fortune” and see what you get. Mine read

“Next Friday will not be your lucky day. As a matter of fact, you don’t
have a lucky day this year.”

This and other random nuggets of information, quotes or entire randomness will be output by this program. You can combine this with cowsay to great effect, for example:

fortune | cowsay
 ________________________________________
/ Q: Why is Christmas just like a day at \
| the office? A: You do all of the work  |
| and the fat guy in the suit            |
\ gets all the credit.                   /
 ————————————————————
        \   __
         \  (oo)\_______
            (__)\       )\/\
                ||——w |
                ||     ||

Paste that line into your .bashrc or equivalent and ensure a little chuckle, or maybe complete bewilderment, every time you log in!

Another in the “Fun with Unix” series (see the one other post so far on mesg), today’s episode covers a little trick that goes alongside messages.

Here it is:

 _______
< hello >
 -------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

The code to output the above is:

echo "hello" | cowsay

You can tell cowsay to use a different picture, how about this one:

 echo “hello” | cowsay -f elephant
 _______
< hello >
 ———-
 \     /\  ___  /\
  \   // \/   \/ \\
     ((    O O    ))
      \\ /     \ //
       \/  | |  \/
        |  | |  |
        |  | |  |
        |   o   |
        | |   | |
        |m|   |m|

	

Or even:

	
echo “hello” | cowsay -f daemon
 _______

< hello >
 ———-
   \         ,        ,
    \       /(        )`
     \      \ \___   / |
            /- _  `-/  ‘
           (/\/ \ \   /\
           / /   | `    \
           O O   ) /    |
           `-^—’`<     ‘
          (_.)  _  )   /
           `.___/`    /
             `——-’ /

<——.     __ / __   \

<——|====O)))==) \) /====

<——’    `—’ `.__,’ \
             |        |
              \       /
        ______( (_  / \______
      ,’  ,——-’   |        \
      `—{__________)        \/
	

My files are in /usr/share/cowsay/cows so have a look what you have.

Of course you can use these in conjunction with write that I mentioned last time, by using something like:

echo "hello there" | cowsay -f hellokitty | write kevin

Enjoy :)

Tied up with the various issues we’ve had recently with houses, I’ve got a new project. Its to turn my (mother’s) very old laptop into a dumb terminal we can have in the basement in the new house. The kitchen is in the basement and I’m keen not to bring any more hardware into that environment that we need to, just because kitchens are full of liquids and grease.

I’ve got a Toshiba Satellite 210CS, complete with its original “Optimized for Windows 95” sticker. It celebrated its twelfth birthday this year so its not doing too badly! Its had a couple of upgrades from its original configuration – it has a 1GB hard drive, a PCMCIA wirless card that will talk to our 802.11b router, and a memory expansion to take it to 24MB of RAM. The processor is a Pentium 120Hz and judging by the fact that it thinks its June 2nd 2005, its CMOS battery is flat.

On Sunday night (its a bank holiday here so we’ve had Monday off as well) we installed Damn Small Linux (DSL) onto it and hoped for the best. The most impressive thing about this is always trying to boot anything new. This machine predates real PCMCIA standards and predates USB; it has a CD drive but can’t boot from it and often won’t read written CDs. It does have wired network on PCMCIA but can’t boot from that either. And it has a floppy drive … somewhere. So we managed to find the floppy drive, and another machine with a floppy drive in it (we were quite surprised to realise the server has one), and even unearthed a floppy disk in the house. Which is more impressive than it sounds as all our stuff is in storage!

DSL went on like a dream but wrongly guessed the size of the screen on the laptop so on the first attempt when I thought it had stopped and I pressed return a few times to shift everything up the screen a bit, I discovered I had answered “no” to the question “would you like a boot loader?”! So we did that again and now its working fine.

Even more impressively, the DSL installation is happily driving the PCMCIA wireless card, out-of-the-box. Last time we re-installed this machine (we think 3 or 4 years ago) we gave up with getting a binary distro working and Kevin compiled some special Gentoo for it. I was impressed how painless this was, so a big thanks to the DSL people, I must send them some fanmail. Or money, maybe.

The plan is just to use the command line to ssh up to the main in-the-house server and use that for checking mail. We can use lynx and command-line chat equivalents if we get desperate too :)

¹ If you were hoping for an update, we’ve commissioned the searches but must complete by the end of May to avoid losing the mortgage. Watch this space.

This is the first in a mini-series of articles about using Linux/Unix to do things other than view logs and edit files. I’m 26 and find that many of my peers weren’t exposed to Unix servers at university, so they miss out on this. If you have any suggestions of things to include in the mini series, let me know please!

Write messages

So to pop up a message on another user’s PC, you’d usually use MSN, right? Well if you’re both logged into the same server there is another way. Just echo your message and then send the program write to get it to the person. Like this:

echo “Hello Kevin” | write kevin

Kevin will get a message on his screen which says:


Message from lorna@server on pts/1 at 22:14 ...
Hello Kevin
EOF


Silence please

To turn off receiving messages, you need to change your mesg setting, by setting it to n:

mesg n

Not surprisingly, you can turn it back on with:

mesg y

That’s today’s installment, have fun!