What filesystem is safe for a Linux OS on a USB?

jefro · 01-10-2013, 08:42 PM

I had to look that up myself.

"On Linux, if extlinux is installed and the target USB drive is ext2 or ext3, extlinux is used instead; the config file is installed in /extlinux.conf. The partition to which it has been installed is also marked as active.
Hard Disk (frugal) install mode"

However, I'd suggest that the OP just use the usb as if it were a real hard drive and follow the bt installer. I use ext2 and no swap partition for usb flash drives. To be safe, use ext4. Too much overhead to run an os from usb and journal and swap space in my opinion. Easy enough to make a new flash drive by the time it fails.

jschiwal · 01-15-2013, 06:10 PM

Quote:

Originally Posted by TobiSGD

Just for clarification, this is just a convention, no necessity. There is no technical reason that would stop you from starting the first partition at sector 1024 or sector 2657, apart from possible alignment problems. But of course most of the time it is a good idea to use the standard options.

Yes. But if a tool like fdisk or gparted was used to create the partition, then it will start on 63 for older partitions and 1024 or 2048 for newer ones. One tip is to make sure to set the block/sector size (on fdisk) to 512 bytes unless the drive is over 2-TB. Then it will use a minimum of 1024 bytes for the block size.

SD cards operate on 1/2 M chunks at once. What I don't understand is why 2048 is used instead of 1024. 1024*512 = 1/2 Meg. Maybe it's looking ahead to when SDD drives are over 2 T in size and work on 1024 byte blocks.

TobiSGD · 01-15-2013, 09:01 PM

Quote:

Originally Posted by jschiwal

One tip is to make sure to set the block/sector size (on fdisk) to 512 bytes unless the drive is over 2-TB. Then it will use a minimum of 1024 bytes for the block size.

Would you like to explain that? It may be possible that I misunderstand, but AFAIK a) can fdisk not handle disks larger than 2TB, since you need GPT for them, and b) the physical blocksize is not dependent on the size of the disk, I know at least of 1TB disks from WD with 4KB physical blocksize.

Quote:

What I don't understand is why 2048 is used instead of 1024. 1024*512 = 1/2 Meg. Maybe it's looking ahead to when SDD drives are over 2 T in size and work on 1024 byte blocks.

Current SSDs use erase-block sizes of 128KB, 256KB and 512KB (dependent on manufacturer/model). Partitions have to be aligned to those sectors or you will have serious impacts in write performance and higher wearout. So starting the first partition at sector 2048 makes sense, if you think about possible future models with erase-block size of 1024KB.

jpollard · 01-16-2013, 10:54 AM

Quote:

Originally Posted by lleb

nope, in order to contain an MBR, it must be fat. the other partition can be any format it matters not.

Even when creating a Live bootable USB you must create a dos bootable partition first, then you can split the rest into what ever file system type you desire. ext2,3,4,riser, etc...

An MBR is outside of any filesystem. So filesystem type is irrelevant.

The only things to select a filesystem on are how well it supports the device. Ext4 has the advantage of supporting trim mount - this can take advantage of the devices capabilities by avoiding useless writes (writing nulls when they go to the wrong block). Ext2/3/4 will all work.

If you are trying to share files with no security restrictions, then FAT is the way to go.