Linux – Using APT how can I install phpMyAdmin without ‘apache2’ and all of the other gumpf

What is debian-sys-maint used for?

One major thing it is used for is telling the server to roll the logs. It needs at least the reload and shutdown privilege.

See the file /etc/logrotate.d/mysql-server

It is used by the /etc/init.d/mysql script to get the status of the server. It is used to gracefully shutdown/reload the server.

Here is the quote from the README.Debian

* MYSQL WON'T START OR STOP?:
=============================
You may never ever delete the special mysql user "debian-sys-maint". This user
together with the credentials in /etc/mysql/debian.cnf are used by the init
scripts to stop the server as they would require knowledge of the mysql root
users password else.

What is the easiest way to restore it after I've lost it?

The best plan is to simply not lose it. If you really lose the password, reset it, using another account. If you have lost all admin privileges on the mysql server follow the guides to reset the root password, then repair the debian-sys-maint.

You could use a command like this to build a SQL file that you can use later to recreate the account.

mysqldump --complete-insert --extended-insert=0 -u root -p mysql | grep 'debian-sys-maint' > debian_user.sql

Is the password in /etc/mysql/debian.cnf already hashed

The password is not hashed/encrypted when installed, but new versions of mysql now have a way to encrypt the credentials (see: https://serverfault.com/a/750363).

Many people seem to be afraid of mixing stable with testing, but frankly, testing is fairly stable in its own right, and with proper preferences and solution checking, you can avoid the "stability drift" that puts your core packages on the unstable path.

"Testing is fairly stable??", you ask. Yes. In order for a package to migrate from unstable to testing, it has to have zero open bugs for 10 consecutive days. Chances are that, especially for the more popular packages, somebody is going to submit a bug report for an unstable version if something is wrong.

Even if you don't want to mix the environments, it's still nice to have the option there in case you run into something that requires a newer version than what is in stable.

Here's what I recommend for setting this up:

First, create the following files in /etc/apt/preferences.d:

stable.pref:

# 500 <= P < 990: causes a version to be installed unless there is a
# version available belonging to the target release or the installed
# version is more recent

Package: *
Pin: release a=stable
Pin-Priority: 900

testing.pref:

# 100 <= P < 500: causes a version to be installed unless there is a
# version available belonging to some other distribution or the installed
# version is more recent

Package: *
Pin: release a=testing
Pin-Priority: 400

unstable.pref:

# 0 < P < 100: causes a version to be installed only if there is no
# installed version of the package

Package: *
Pin: release a=unstable
Pin-Priority: 50

experimental.pref:

# 0 < P < 100: causes a version to be installed only if there is no
# installed version of the package

Package: *
Pin: release a=experimental
Pin-Priority: 1

(Don't be afraid of the unstable/experimental stuff here. The priorities are low enough that it's never going to automatically install any of that stuff. Even the testing branch will behave, as it's only going to install the packages you want to be in testing.)

Now, creating a matching set for /etc/apt/sources.list.d:

stable.list: Copy from your original /etc/apt/sources.list. Rename the old file to something like sources.list.orig.

testing.list: Same as stable.list, except with testing.

unstable.list: Same as stable.list, except with unstable, and remove the security lists.

experimental.list: Same as unstable.list, except with experimental.

You can also add a oldstable in sources.lists.d and preferences.d (use a priority of 1), though this moniker will tend to expire and disappear before the next stable cycle. In cases like that, you can use http://archive.debian.org/debian/ and "hardcode" the Debian version (etch, lenny, etc.).

To install the testing version of a package, simply use aptitude install lib-foobar-package/testing, or just jump into aptitude's GUI and select the version inside of the package details (hit enter on the package you're looking at).

If you get complaints of package conflicts, look at the solutions first. In most cases, the first one is going to be "don't install this version". Learn to use the per-package accept/reject resolver choices. For example, if you're installing foobar-package/testing, and the first solution is "don't install foobar-package/testing", then mark that choice as rejected, and the other solutions will never veer to that path again. In cases like these, you'll probably have to install a few other testing packages.

If it's getting too hairy (like it's trying to upgrade libc or the kernel or some other huge core system), then you can either reject those upgrade paths or just back out of the initial upgrade altogether. Remember that it's only going to upgrade stuff to testing/unstable if you allow it to.

EDIT: Fixed some priority pins, and updated the list.