Installing Apps on External Hard Drive

You need to provide more details before anyone can offer a suggestion. Why won't it let you? Is there an error message? If so, what does it say? What applications are they?

Jason,

Most applications will work if they are located on an external drive. The installer, however, might not be able to understand an attempt to install the application directly to it. My advice would be this: Let the installer place the application in "Applications" on your startup disk, then copy the application to the external. Luanch the copy on the external to make sure everything works correctly. If it does, you can then delete the original in "Applications," thereby recovering your disk space.

Scott

Scott is right. You can install applications in the Applications folder on your internal HD and then move them to your external disk.

There's one caveat, however. It is best NOT to move certain apps (particularly those that are bundled with Mac OS) out of the Applications folder. There are at least two reasons for this:

1. If Software Update does not find an app in the Applications folder, it will not show any updates for it.
2. If you download an update manually, it will likely not update the apps outside the Applications folder. Most updates only contain the pieces that need to be updated and not the entire application.

Some third-party applications use Apple's Installer to install and update their components. These apps will also be broken (or won't update) if you move them from their original locations.

Many applications, however, are simple drag-installs. Those can be freely moved to any location (including external hard disks).

What would happen if you created an alias inside the Apps folder that points to an auxilary folder on the external device? Or would you have to use unix to make it a hard link rather than a symbolic link?

Or would you have to use unix to make it a hard link rather than a symbolic link?

Most likely. Moreover, this may also not work. Apple's Installer.app coupled with Software Update are not a... very sophisticated concept, to put it mildly. Don't forget that most applications now are, actually, folders with other files and folders inside. When the Installer.app updates the contents of such folder, it needs the exact path to all the components to be updated.

Matt,

Or would you have to use unix to make it a hard link rather than a symbolic link?

No can do. Hard links cannot span file systems. A hard link is nothing more than a separate, distinct name for a given file system object. As such, and just like the original name, it points directly to the physical location of the data on the HD. Hard links are useful if one wants to have multiple names, in multiple file system locations, point to the same file. Any of these names can be deleted, but as long as at least one remains, the data stays put. Symbolic links, on the other hand, point only to the orignal name, not the data. If the original name is removed, the data is lost.

Aliases and symbolic links are not exactly the same. In basic terms, a sym link is more of a file system artifact, while an alias is more an artifact of the GUI. Because of this, sym links have a better chance of success in usages such as this (moving the "Applications" folder to a secondary volume).

In most cases, using a sym link in place of the actual "Applications" folder will work well, but there are many potentials for calamity. Put simply, well-coded applications, application updaters, and installers should never have difficulty with sym links in place (even the Apple updaters; I would be willing to guess that these would be just fine). Unfortunately, this is not always the case in real life. I don't recommend against an attempt to do this, but don't be surprised if problems occur. Your mileage may vary 😉

Scott

Jason,

Any "auxiliary" files that are installed, say somewhere in the "Library" folder, must remain where they are. Only the applcation, itself, can be moved to another volume.

If you don't have enough room at present, try moving some other application(s). If they work well on the secondary volume, delete the originals to create enough space to install the new app.

Scott

If you don't have enough space on your hard drive to install an application, then you probably have bigger problems. You should always have at least 10-15% of your drive free for the OS X to use as virtual memory, etc. If you have very little free space, you'll get poorer performance from your computer and could cause corruption to your file system.

That's about 20% free space, which means that you're okay, but you don't want to get much less than that. You should see about moving old files that you don't need to some other backup medium, and move any applications and data that you can to your other drive as well.

what if I don't have enough space on my hard drive to install [applications]?

Well, this is not good. This means you don't have enough room for virtual memory swap files. Consider freeing some room on the HD. Chances are your iPhoto and iTunes libraries take most of the space. These can be moved to another location (or archived to CDs/DVDs).

what about any files or folders that are copied to the library?

No, you can't freely move the contents of the Library folder. Apps wouldn't know the new location and there's no way for you to tell them that.