Install applications on LiveCD/USB

I can say that yes it is possible to run Ubuntu from a usb in that fashion, but I would not suggest it.

Flash drives have a set number of writes, hundred of thousands in some cases, and that sounds large but for an OS saving and reading files constantly, it wont take long before that pen drive reaches its limit.

Short answer: yes, its possible and as an experiment interesting. As a permanent solution no.

There is a way to have a portion of the usb disk dedicated to new files on the livecd desktop. When you make the live usb via the "Startup Disk Creator" you need to select "Stored in reserved space", I'm not sure if this only effects the docs and settings and not new apps, but it should.

The other easier and faster option is to use an installation on a USB stick instead of a livecd. You need a USB drive which is 4GB or more and when doing the install you need to select the usb drive as the target (use entire disk) and then at the end of the installation you need to select Advanced and put the usd drive in as the boot loader location. This is the only complexity for making a fully functional install on a stick.

If you have created the usb using the live usb creator or a similar tool no, they provide a semi-peristent option which allows to change /home contents but not the root filesystem.

To be able to update an USB install you will need to do a full persistent install as described at the answers for the following question: How do I install Ubuntu to a USB key? (without using Startup Disk Creator)

What you're talking about doing refers to having a persistent USB Drive. With what you currently are using yes, you can reboot it but no, you won't be able to save anything to it. An option have though is to make a LiveUSB that is able to be persistent, (Able to hold changes and save them, like saving a word document etc.) then you'd most likely be able to do what you're asking. To do this I recommend you use a USB Flash drive that has a minimum of 4GB of free memory, preferably 8GB if you have it. A (hopefully anyway) simple way to do this follows.

Please Note: This tutorial is based for those with Windows Systems, and are trying out GNU/Linux on the aforementioned system.

What You Will Need

• The Universal USB Installer Program.
• A computer with an Internet Connection.
• A GNU/Linux ISO image. Ubuntu, Fedora, Kubuntu, Etc...

What To Do

1. DOWNLOAD or run the Universal USB Installer Program.
2. Browse and select your chosen GNU/Linux ISO Image. NOTE: If you don't have one you will be given the option to download it before writing it to your chosen drive.
3. Browse for and select your chosen USB Flash Drive.
4. MAKE SURE you have chosen the right flash/external drive BEFORE you write the ISO image to it as ALL data will be lost when this process is completed!!!
5. Write the ISO image to the flash drive, choosing if you wish to have a persistent storage and if so how much memory to allocate for said storage.
6. Restart your computer with the flash drive connected, boot to the flash drive, and enjoy your external USB Drive! Hope this helps you!

P.S. If you need more info please do not hesitate to let me know...

Using usb-creator.exe from the iso or Startup Disk Creator from the Live CD you can select "Stored in reserved extra space" and specify up to 4GB of persistence space. This will allow you to install additional applications. You may have a hard time installing proprietary drivers and some applications. And you should not do updates or upgrades with a persistent drive.

If you need these you can always do a full install to USB.