Can I have full Linux on an external HDD?

boot system-installation security external-hdd portable

34,563

Yes, you can have a full linux operating system installed on an external hdd. See these links,

You can also have a persistent live Ubuntu system according to these links,

Symlinks work, they relate to the mount point and directory path, not to the drive's device letter.
Unless you explicitly write to the internal drive, nothing will be written there.
Things are complicated, if you have encrypted your internal drive. Otherwise, the data will be possible to access at least 'with sudo' (to get elevated permissions).
You probably need some authorization to access the network.
If you can boot from the external drive (USB or eSATA), this should not affect the internal drive, but some UEFI systems are tricky. For example, if you boot Windows, while your external drive is connected, and Windows does some updates/upgrades, booting your external drive might be damaged.
Old computers boot only in BIOS alias legacy mode. Most new computers (from around 2011) can boot both in UEFI mode and BIOS mode alias CSM alias legacy mode.
The UEFI/BIOS system can be protected with a password, and if that is the case you need the password to boot. The owner will not be happy if you try to bypass it.

34,563

Jacob

History I was born at 1998 in Czech Republic. Sadly at the age of 5, I was diagnosed with Asperger syndrome what explaining my poor social abilities. People like me are marked as "retards" and no one IT school wants accept me. I wanted to show them how terribly they were wrong in me, not only in me but in other people like myself. At the age of 12, I started working with a tool called Game Maker, and at the age of 15 I started to learn the C # programming language. When I was 16, I finished my first game that I could not publish due to the copyright of the music used in the game. In autumn 2017, I finished the first public game named War City. Character Mealchonic introver with a high level of intelligence but very weak social capabilities. I always liked anime and manga, I also like nightcore. I do not care what other people think about me and I will always do what I like, regardless of the opinion of others. I love old games, especially games for GameBoyAdvanced or PlayStation1 also I like games from the late DOS era and the early Windows era. These old games have something that is missing in the new games, something indescribable, something like.... soul.

Updated on September 18, 2022

Comments

Jacob over 1 year
I'd like to carry my computer everywhere I go but big bag with "Lenovo" label is kinda thief-magnet. I want to to use other computers only to provide physical resources but carry everything digital with me. Looks like a portable Linux distro is good choice but I'm unsure about few things.
- Symlinks. This is serious problem with Windows but I'm unsure about Linux. Are symlinks (and paths in general) going to work with different drive letters? Various computers are going to give my external HDD various drive letters and I really want to know if it going to work.
- If I boot from external disc and save everything to external disk and basically don't touch any of hosting computer's disk, will there be any leftover files?
- I still have lots of files on my original laptop's HDD. Can I access those files even from admin-protected directories? Or do I need to input admin password? Can these files be damaged due to having different line endings? Do I need to convert them somehow? Can all files generally be used both in Windows and Linux (including .exe using Wine)?
- Can Linux use the network connection of original computer without a Wi-Fi password or Ethernet link without authorization of some kind?
- Can I boot from an external HDD without any damage being done to computer in case computer's original HDD contains different OS? How can I prevent damage?
- Can I boot from external HDD even if hosting computer does not support UEFI? How?
- Can the boot menu be locked by a password, so that the computer requires a boot menu password on every boot? Can I bypass it somehow in order to boot from external HDD without permanent changes done to hosting computer?
After Edit Note: I'm still student. I don't want use company computer but rather school computer. Need to say I'm absolutely sure that USB ports work fine (I usually use portableapps platform from my USB stick). I'm also sure USB booting works because school computers have no disc mechanic. Also there is no reason for destroying USB ports because students need to carry some work home, besides the fact than we are overseen by teachers all the time. Main reason for this is to have my work (I'm indie game dev) available all time without leaving any of my files on computers of others. I also disagree with Bill and his (terrible, by my option) Windows 10 that are currently installed in school for no real reason.
- pim about 6 years
  
  Welcome to [askubuntu.com/tour](askubuntu)! You will probably get better quality answer if you only post one question per post. (reference)
- Takkat about 6 years
  
  For a start, you may be interested in this: askubuntu.com/questions/16988/… but you may have to consider that most external computers will not boot from USB.
- pim about 6 years
  
  @sudodus, sure the link does not work and now I can't fix it... It should have been : askubuntu
- pim about 6 years
  
  @Takkat, what do you mean by "external computer" and why do you say that most won't boot on USB?
- sudodus about 6 years
  
  @pim, You can create a new (correct 'welcome') comment and remove the old one and the comment answering to me (and I remove my comment to you) :-)
- Takkat about 6 years
  
  @pim: to let anybody boot a computer with an USB key is a huge security risk. Most admins will not allow that (they may even have to destroy all USB ports mechanically).
- sudodus about 6 years
  
  You may borrow a friend's computer, but not a company's computer or a public computer.
- sudodus about 6 years
  
  If you can and are allowed to boot your school computers from USB, fine :-) I think you can create a USB boot drive with an installed system, that works well both in your school computer and your home computer, at least if both work without proprietary drivers (for example graphics driver or wifi driver).
- Jacob about 6 years
  
  @sudodus If i install proprietary drivers (like printer) it will be ignored on computer where is device not connected, right ?(i hope so)...Booting is usually not allowed because it is "E" type apprenticeship(for people whos require individual treatment because of some handicap or retardation, like myself with Asperger's Syndrome)but teachers are aware of my computer skill and intellect so I'm sure I'll be able to speak my way through
- sudodus about 6 years
  
  Printer drivers are OK to install. Good luck :-)
- bogdan about 6 years
  
  Possible duplicate of How do I install Ubuntu to a USB key? (without using Startup Disk Creator)
- Jacob about 6 years
  
  @bogdan Not a duplucate. I was not asking about installation process,I was asking about details of portability of installed system.
pim about 6 years

I think the question about drive letter is also a question about will /dev/sda will always be mounted at the same mountpoint. And can be answered as ubuntu use UUID.
sudodus about 6 years

@pim, You are right, partitions in the [first] internal drive /dev/sda might or might not be mounted automatically. In any case, if/when mounted, they will be mounted separately from the system partitions of Ubuntu in the USB drive.