I have a Linux dist burned on a USB flash drive, which I sometimes use to boot into.
Everytime I boot into it I get a clean system - meaning if I downloaded something into it, it disappears when I boot into it the next time.
So my question is: is it dangerous to download stuff when using a usb boot? Where does the system store my downloads? Can it override data in my hdd?
Thanks!
is it dangerous to download stuff when using a usb boot?
Generally speaking, it is not any more dangerous than downloading data while booted off of the regular HDD. Any precautions you would take while booted off of the HDD would also apply while booting off of USB.
Where does the system store my downloads?
Normally, with a USB install, either the whole system will be running off of your RAM, which means files are not downloaded to any "persistent" location (this is called Live mode), or the USB stick itself will have a persistent location/partition for files to be saved to, and modifications to be stored (Full Install mode). So, by default, files will either be downloaded to RAM, or to the USB stick. Unless you specifically tell it to send them to your HDD. Leading to your third question...
Can it override data in my hdd?
Not in the way you are probably thinking. Most USB installs will generally have the ability of accessing your HDD, especially if it is formatted in one of the standard, common file system types (ext3/4, NTFS, FAT, HFS+, etc). This is why Live installs are commonly used to troubleshoot problems with a HDD install. However, this does not mean it will indiscriminately write to the HDD without regards of the HDD contents. If you were to save any downloaded files to the HDD, these "writes" will act the same way that any normal write would, when booted from the HDD. Meaning, the file will be written to empty space, and within the existing file system in the HDD. You would notice this because you would still have to navigate the existing file system in the HDD, so if while booted to HDD you created a folder called /variousThings, when booted to USB and accessing the HDD, you would still see and be able to write the file to /variousThings.
So, in short, no, booting from USB would not damage your HDD unless you specifically were out to do that.
rm -rfs every filesystem it can find).
Live-Images usually shouldn't mount your HDD automatically, so you can't actually save files. They are probably just kept in memory if you haven't set up your USB drive with a "persistent" partition for such purposes (or manually mounted a drive).
Although those drives aren't mounted you can still access them on the device level and overwrite them with the dd command, for example, so you aren't competely save from malicious attacks.
Since it's a Live Distro and it's booting off the USB, that's where the files are temporarily stored, the reason they don't save is because there are tow types of installations from a USB.
Persistent Live USB and Full Linux Install on USB
Live USB is a good way of testing out Linux distro without making changes to your computer. Unknown to many, there is a data persistency mode in the Live session where you can make changes and save files to your USB drive and the data will persist even after shutting down the live session. After testing out the live session, you can also install the distro to your USB drive instead of the internal hard drive. Both methods allow you to boot Linux from a USB drive and save data to it. So what are the differences between the two and which one should you use?
So on to your question, is it safe? I would say it's as safe as any other operating system, it depends on what you're downloading.
Since you can manually mount your hdd, that means other people can as well, if you download a dodgy script or some malware that could auto-mount your hard drive in the background, that means it has access to it.
You could run your Linux Distro within a Virtual Machine which would be more secure than a Live Distro, in case you want to download Dodgy Files.
It has been my experience that certain distros are "LIVE". These allow you to boot to the OS and play around, but when you power them off everything is reset and the next time you boot all changes are lost (even configurations to network). If you want to save the changes that are made you will need to do an install to a local disk. If you have the option to add a partition to the USB flash drive you may be able to retain downloads saved to a secondary partition.
