apt-get hangs when upgrading mysql-server-5.1

Apparently the update is waiting for the server to start and for some reason it does not. To fix the problem there are several possibilities.

The easiest:

1. Open a new terminal, and run:

   sudo services mysql start
   

More complicated but sometimes necessary: (this is handy when you do not have access to another terminal):

1. Press "^z" (Ctrl + Z) which will "STOP" your job. Then run:

   sudo services mysql start
   

2. Once the server is started type the following and hit Enter:

   fg 
   

   This will place your "STOPPED" job back in the foreground and continue where it left off.

Try going a level below apt, after backing up your databases:

sudo dpkg -r mysql-server
sudo apt-get check    # verify that apt's metadata is okay
sudo apt-get install mysql-server

added:

Since dpkg -r is choking try dpkg --purge and failing that get the package contents with dpkg -L mysql-server-5.1 zap them and then muck about in /var/lib/dpkg.

I've never seen things get that hairy, sorry.

if at first you don't succeed

I'm sorta thinking aloud here, forgive me. The mysql-server meta-package contains or requires these packages:

libdbd-mysql-perl
libdbi-perl
libhtml-template-perl
libnet-daemon-perl
libplrpc-perl
mysql-client-5.1
mysql-client-core-5.1
mysql-server
mysql-server-5.1
mysql-server-core-5.1

The meta-data for package management is delightfully decoupled, there are central repositories but the packages stand alone. /var/cache/apt/archives is where *.deb files that have been installed live.

First, force dpkg to forget about these packages (at the risk of failure to remove some files that we're going to replace anyway).

for i in mysql-server-core-5.1 mysql-server-5.1 ... ; do
    sudo dpkg -r --force-remove-reinstreq $i
done

Then get the .deb files needed for a full install:

sudo apt-get install --download-only mysql-server

and then try installing them one by one:

cd /var/cache/apt/archives
sudo dpkg -i mysql-server-core-5.1_5.1.41-3ubuntu12.3_i386.deb

if you have problems there, try:

sudo dpkg -D77777 -i mysql-server-core-5.1... > 2>&1 /tmp/dpkg.log.$$

And try and find the relevant lines out of the zillion in the logfile and post them here. Good luck and godspeed.

I was having this problem because it was a copy of a VM so I had changed the IP address of the server but didn't change the bind-address in the my.cnf file. Once I changed the bind-address to match, the update didn't hang and completed successfully.