By default, Linux can only see his own partition(s).
But what if you need some data stored on a partition readable by Windows (wich uses an NTFS or FAT filesystem)?

Of course Linux allow you to read the content of both FAT and NTFS partitions, but you have to mount them: I’ll show you how.

A brief prologue is needed: mount a filesystem means that you virtually place the whole partition on a directory under the root directory /, and you specify what the system is allowed to do with it: you can mount a filesystem as read-only, or as writable.

The command is mount, and the syntax is the following:

Let’s explain: this command mounts the filesystem found on device (which is formatted with filesystem_type) on directory (properly called mount point) with the specified [options].
Devices are usually listed under /dev; hard disk partitions are identified from the letters hd, followed by the disk order in letters (A for the first disc, B for the second, and so on) and then the number that identifies the number of the partition on the phisycal drive (1, 2, 3…).

Usually, the only options you will need to care about are -ro for read-only and -w for read-write.

Let’s make a practical example.
Say that you want to mount the partition in which is installed Windows XP, that is on /hda2 (then, /dev/hda2 under Linux) and you want to show its content, as read-only, in /mnt/windows. The command for that will be the following:

Now, you can go to /mnt/windows, and you will see your so-called C: disc here. Quite simple, isn’t it?

So, now we know how to manually mount partitions.

How to mount partitions automatically at the system boot?

The key is on this file: /etc/fstab. This file contains informations about partitions and storage devices on your computer. During the boot, Linux reads its instructions and mount filesystems accordingly.
In this file, every row contains informations about a partition. The structure of a row is:

Let’s explain:
Device is your device (/dev/hda2 accordingly to the previous example), mount point is the directory where you will see your data, type is the filesystem (e.g. “ntfs” for windows), options have to be comma-separated (I will return on them in a moment), dump and check refers, respectively, to “do you want a backup of this” and “do you want the system to check this disc”. Both these values can be 0 or 1, respectively for True or False. If you’re mounting a Windows partition, leave 0 for both.
Options: they are almost the same allowed for mount command. When mounting a Windows unit, the only really useful options are: ro (or rw, respectively for Read-only and Read-write), and user (or nouser: default is nouser, and if you don’t change this to user, the system will not mount your device unless you are logged in as root).

Going on with the example, a row in /etc/fstab that will automatically mount the Windows XP partition found on /dev/hda2 in /mnt/windows as read-only, would look as the following:

Now, every time you boot, you will able to read contents from C: into /mnt/windows!

If you wish, you can read a more extensive documentation on fstab.

NOTE ON WRITING ON WINDOWS PARTITIONS: Linux support to write mode in NTFS partitions is experimental, and depending on the distribution in use. This means that write to NTFS from Linux could lead into unrecoverable errors. Use it at your own risk!

REMEMBER: default option in fstab (if you are going to use it instead of the suggested ro,user) mounts the filesystem with write privileges.

If you have installed MySQL server in the standard directory /usr/local/mysql, do not read this post. Else, you may want to know

how to use MySQL shared libraries on your Linux system

For organization purposes, I have installed MySQL in /home dir (which is a separate partition), precisely in /home/server/mysql. Thus, I keep mysql/var, directory (which contains databases) safe from heavy system changes.

My system did not recognized the shared library libmysqlclient, that is under /home/server/mysql/lib/mysql.
How do you tell Linux “Hey, you will find the library here, go and use it”?

Just edit the file /etc/ld.so.conf and add the path to your library. Then, reboot or give this command:

to register new libraries.

Compiling programs that require MySQL components

Another issue you’ll have to deal with when your MySQL is installed in a non-standard path, is the source compilation and use of programs that require some MySQL components.

For example, I use a C program that has this header on its source:

I got errors related to paths when compiling this source.
The solution is not changing the source in order to make #include lines match real paths, but consists in telling the compiler where mysql directory is. Compile with such a command line (or change your Makefile accordingly):

How to automatically run a command or program at Linux system start-up:

The file where boot process sequence is defined is: /etc/inittab
Log in as root, open it with a text editor, and locate a line similar to this:

After that line, you can start adding your custom auto-run process calls. Syntax is:
id:runlevel:action:process

So, if you want a program to be started, you can add one or more lines like followings:

Where s0 and s1 are custom defined IDs, 2345 are runlevels the rules applies to (all but shutdown and reboot), and wait means that the system should wait for the command to be executed before doing something else.

Pay attention do not change wait flag into respawn, or else you’ll have the system freezed at next reboot!

Apply changes made to inittab without rebooting

To see the effects of any changes you made to /etc/inittab without rebooting your machine, just type this command:
init q