How to install a Trusted Certificate Authority on Windows 7

At my company AppCove, we have our own certificate authority that we use with development servers and sites.  This allows us to (at no additional cost) use HTTPS and SSL for all of these alternate domains and subdomains.

The downside is that our certificate is not trusted by any stock browser or operating system.

Therefore, to prevent getting an ugly and scary SSL warning, anyone who needs to visit these (private audience) sites must first “trust” our certificate authority.

A note on security.  If you are telling your computer to trust a certificate authority, then you must really actually “trust” that authority.  If the signing key fell into the wrong hands, then they could create fake certificates for other sites you visit, like, and intercept your data.  At AppCove, we use aggressive security measures to protect the certificate authority key (as we do for customer data and applications).

In this example, I am causing my Windows 7 workstation to trust appcove-ca-cert.pem.crt















— Start of slight detour — 

If you want to verify it was installed, do this.  Otherwise, skip the next 2 screens.



— End of slight detour —



At this point, you should be able to visit any HTTPS site that was signed with this certificate authority and your browser will indicate that it is a secure connection.

Introducing FileStruct (for Python)

FileStruct is a lightweight and fast file-cache / file-server designed for web-applications.  It solves the problems of “where do I save all of those uploads” that has been encountered time and time again.  FileStruct uses the local filesystem, but in a sensible way (keeping permissions sane), and with the ability to secure it to a reasonable level.

Here is a simple example of taking an image upload, resizing, and saving it:

with client.TempDir() as TempDir:
   open(TempDir.FilePath('upload.jpg'), 'wb').write(mydata)
   TempDir.ResizeImage('upload.jpg', 'resize.jpg', '100x100')
   hash1 = TempDir.Save('upload.jpg')
   hash2 = TempDir.Save('resize.jpg')

Design Goals

Immutable Files

FileStruct is designed to work with files represented by the SHA-1 hash of their contents. This means that all files in FileStruct are immutable.

High Performance

FileStruct is designed as a local repository of file data accessable (read/write) by an application or web application. All operations are local I/O operations and therefore, very fast.

Where possible, streaming hash functions are used to prevent iterating over a file twice.

Direct serving from Nginx

FileStruct is designed so that Nginx can serve files directly from it’s Data directory using an X-Accel-Redirect header. For more information on this Nginx configuration directive, see

Assuming that nginx runs under nginx user and file database is owned by the fileserver group, nginx needs to be in thefileserver group to serve files:

# usermod -a -G fileserver nginx


FileStruct is designed to be as secure as your hosting configuration. Where possible, a dedicated user should be allocated to read/write to FileStruct, and the database directory restricted to this user.


FileStruct is designed to be incredibly simple to use.

File Manipulaion

FileStruct is designed to simplify common operations on files, especially uploaded files. Image resizing for thumbnails is supported.

Temporary File Management

FileStruct is designed to simplify the use of Temp Files in an application. The API supports creation of a temporary directory, placing files in it, Ingesting files into FileStruct, and deleting the directory when completed (or retaining it in the event of an error)

Garbage Collection

FileStruct is designed to retain files until garbage collection is performed. Garbage collection consists of telling FileStruct what files you are interested in keeping, and having it move the remaining files to the trash.

Backup and Sync with Rsync

FileStruct is designed to work seamlessly with rsync for backups and restores.

Atomic operations

At the point a file is inserted or removed from FileStruct, it is a filesystem move operation. This means that under no circumstances will a file exist in FileStruct that has contents that do not match the name of the file.

No MetaData

FileStruct is not designed to store MetaData. It is designed to store file content. There may be several “files” which refer to the same content. empty.logempty.txt, and empty.ini may all refer to the empty fileData/da/39/da39a3ee5e6b4b0d3255bfef95601890afd80709. However, this file will be retained as long as any aspect of the application still uses it.

Automatic De-Duplication

Because file content is stored in files with the hash of the content, automatic file-level de-duplication occurs. When a file is pushed to FileStruct that already exists, there is no need to write it again.

This carries the distinct benifit of being able to use the same FileStruct database across multiple projects if desired, because the content of file Data/da/39/da39a3ee5e6b4b0d3255bfef95601890afd80709 is always the same, regardless of the application that placed it there.

Note: In the event that multiple instances or applications use the same database, the garbage collection routine MUST take all references to a given hash into account, across all applications that use the database. Otherwise, it would be easy to delete data that should be retained.

How to Generate a SSH Keypair (public/private) on Windows

Have you ever been asked to generate an SSH keypair in order to gain access to a server, github, or an sftp site?

Here is how on windows.

First, download puttygen.exe from here:


Second, run puttygen.exe and follow these instructions:

(except, put your name instead of Sharon)

(On step 8, copy and paste this and send it to whomever requested it)

puttygen instructions

Simulating ENUM in PostgreSQL using CHECK expression

PostgreSQL is a very powerful database. One of the things that seems missing when moving from MySQL is the ability to simply create an enumeration. ENUM is nice when you have a programmatically-semantic set of values for a field.

In PostgreSQL, you have several choices. But one simple one is to create a Check expression, like follows. Skip the IS NULL part if you don’t want the field nullable.

   CHECK (
      "TransferStatus" IS NULL 
      "TransferStatus" = ANY(ARRAY['TransferComplete', 'TransferFailedNoAnswer', 'TransferFailedProspectLost'])

git checkout -b –no-track

Ever want to checkout a new git branch from another branch without setting up tracking?

Here is the longhand way:

git checkout old-branch
git branch new-branch
git checkout new-branch

But there is a quicker way:

git checkout -b new-branch old-branch

… which does the same thing, albiet in one command.

HomeSchool Software: Review, Rendering, and Printing

After several intense programming sessions, I got the HomeSchool software in a quite suitable place for us to be able to use it to produce a log and portfolio.

I must say, it’s looking pretty nice!  It is rather amazing to look back at the year, and see in detail what was going on with Eli.

One of my favorites is on page 159 (read the letter on the telephone pole):


Here is a screen shot of the book view: