How do I get an equivalent of /dev/one in Linux

Try this:

dd if=<(yes $'\01' | tr -d "\n") of=file count=1024 bs=1024

Substitute $'\377' or $'\xFF' if you want all the bits to be ones.

Well, you could do this:

dd if=/dev/zero count=1024 bs=1024 |
  tr '\000' '\001' > file

tr '\0' '\377' < /dev/zero | dd bs=64K of=/dev/sdx

This should be much faster. Choose your blocksizes (or add counts) like you need at. Writing ones to a SSD-Disk till full with a blocksize of 99M gave me 350M/s write performance.

pv /dev/zero |tr \\000 \\377 >targetfile

...where \377 is the octal representation of 255 (a byte with all bits set to one). Why tr only works with octal numbers, I don't know -- but be careful not to subconsciously translate this to 3FF.

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The syntax for using tr is error prone. I recommend verifying that it is making the desired translation...

cat /dev/zero |tr \\000 \\377 |hexdump -C

Note: pv is a nice utility that replaces cat and adds a progress/rate display.