Oh. Wait. Just occurred to me: the disk-entries in /dev are block-special files , not directories. Not being directory files, using relative referents (like ../) wouldn't make a lot of semantic sense, I suppose (since one can't cd to a non-directory file-reference). I also suppose it's not solely a #Linux problem, but I don't currently have access to a #BSD or #SysV derived system to compulsively poke at out of curiosity.
In fairness to myself, I don't think I've ever (intentionally) tried to cd to a file? The only reason I (encountered this) "intentionally" tried to do so, today, is because one of the original authors of the Azure plug-ins for #Packer suggested trying it to work around a limitation in the azure-chroot builder.
Interestingly, while that builder's mount_partition parameter exists solely to take partition-number as an argument, it's a string data-type rather than an integer data-type. Also, it does no input-validation, so passing it something other than digits/initegers doesn't make it vomit โฆbut passing it a ../mapper/- string sure does (though only because of a "not found" error, not because it doesn't know how to handle the string-value).
It's, uh, not a well-written plug-in.
#Azure
#IaC
#BuildAutomation