It was probably mounted by udisksd
. Look in syslog. On my system, inserting a USB stick results in this:
Aug 6 15:17:08 ubuntu udisksd[2856]: Mounted /dev/sdb1 at /media/mp/A88B-3652
udisks
tries to provide a unique name for each drive or partition. It searches through all the symlinks that udev
creates under /dev/disk
. For removable media, it looks at the symlinks in /dev/disk/by-uuid
and /dev/disk/by-label
. For nonremovable media, it looks in /dev/disk/by-id
.
The entries in the by-uuid
directory are often, but not always, UUIDs. In your example, the UUID 13f35f59-f023-4d98-b06f-9dfaebefd6c1 was likely generated by a command like mke2fs
, which creates filesystems.
In the case of my USB stick, A88B-3652 is actually the volume serial number of its fat32 partition.
The entries in the by-label
directory are Volume Labels on CD or DVD discs, for example "Ubuntu 14.04 LTS amd64", or filesystem labels created with the -L option to mke2fs
or tune2fs
.
The entries in the by-id
directory are often of the form bustype-manufacturer_device_serialnumber, with a -partn appended for each partition.