Directory Structure

Cygwin knows how to emulate a standard UNIX directory structure, to some extent. This is done through the use of mount tables that map Win32 paths to POSIX ones. The mount table may be set up and modified with the mount command. This section explains how to properly organize the structure.

When you set up the system you should decide where you want the root to be mapped. Possible choices are the root of your Windows system, such as c: or a directory such as c:\progra~1\root.

Execute the following commands inside bash as it is difficult to change the position of the root from the Windows command prompt. Changing the mount points may invalidate PATH, if this happens simply exit and relaunch bash. Create the directory if needed, then umount / the current root and mount it in its new place. You also have to decide if you want to use text or binary mode.

Next, create the traditional main UNIX directories, with the following command (in some shells it is necessary to issue separate mkdir commands, each with a single argument).

/$ mkdir /tmp /bin /etc /var /usr

Next we will initialize the content of these directories.

You should make sure that you always have a valid /tmp directory. If you want to avoid creating a real /tmp, you can use the mount utility to point /tmp to another directory, such as c:\tmp, or create a symbolic link /tmp to point to such a directory.

The /bin directory should contain the shell sh.exe. You have three choices. The first is to copy this program from the Cygnus bin directory. The second is to use mount to mount the Cygnus bin directory to /bin (the advantage of this approach is that your PATH will be shorter inside bash). The third is to make /bin a symbolic link to the Cygnus bin directory.

Note that Cygwin comes with two shells: bash.exe and sh.exe, which is based on ash. The system is faster when ash is used as the non-interactive shell. The only functionality supported in ash is that of the traditional sh. In case of trouble with ash make sh.exe point to bash.exe.

We now turn to /etc. You may want to copy in it the termcap file from the Cygnus etc directory, although the defaults built into the programs suffice for the normal console. You may also use mount or create as symbolic link to the Cygnus etc, just as for /bin above.

Under Windows NT, if you want to create /etc/passwd and /etc/group (i.e. so that whoami works and ls -l replaces the UID with a name) just do this:

/$ cd /etc
/etc$ mkpasswd -l > /etc/passwd
/etc$ mkgroup -l > /etc/group

Future changes to your NT registry will NOT be reflected in /etc/passwd or /etc/group after this so you may want to regenerate these files periodically. Under Windows 9x, you can create and edit these files with a text editor.

The who command requires the /var/run/utmp to exist. Create it if you wish. The system also logs information in /var/log/wtmp, if it exists.

The /usr directory is not used by the Cygwin system but it is a standard place to install optional packages.

You may also want to mount directories such as /a and /d to refer to your local and network drives.

You do not need to create /dev in order to set up mounts for devices such as /dev/null as these are already automatically simulated inside the Cygwin library.