How do I check where devices are mounted?

There are at least three programs I know of that list device mount points:

1. mount - mount a filesystem (used for general mount info too):

   $ mount
   /dev/sda3 on / type ext4 (rw,errors=remount-ro)
   proc on /proc type proc (rw,noexec,nosuid,nodev)
   sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
   ...
   /dev/mapper/lvmg-homelvm on /home type btrfs (rw,relatime,compress=lzo,space_cache)
   /dev/sda5 on /home/muru/arch type btrfs (rw,relatime,compress=lzo,space_cache)
   binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
   systemd on /sys/fs/cgroup/systemd type cgroup (rw,noexec,nosuid,nodev,none,name=systemd)
   

2. df - report file system disk space usage

   $ df       
   Filesystem                1K-blocks      Used Available Use% Mounted on
   /dev/sda3                  30832636  11993480  17249912  42% /
   none                              4         0         4   0% /sys/fs/cgroup
   ...
   /dev/sda5                  31457280   3948600  25396496  14% /home/bro3886/arch
   

3. lsblk - list block devices

   $ lsblk
   NAME                    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
   sda                       8:0    0 465.8G  0 disk 
   ├─sda1                    8:1    0   100M  0 part 
   ├─sda2                    8:2    0  58.5G  0 part 
   ├─sda3                    8:3    0    30G  0 part /
   ├─sda4                    8:4    0     1K  0 part 
   ├─sda5                    8:5    0    30G  0 part 
   ├─sda6                    8:6    0 339.2G  0 part 
   │ └─lvmg-homelvm (dm-0) 252:0    0   1.2T  0 lvm  
   └─sda7                    8:7    0     8G  0 part [SWAP]
   sdb                       8:16   0 931.5G  0 disk 
   └─sdb1                    8:17   0 931.5G  0 part 
     └─lvmg-homelvm (dm-0) 252:0    0   1.2T  0 lvm  
   

Of these three, mount lists all the mountpoints, AFAICT. The others have their weaknesses.

---

4. findmnt suggested by @webwurst is now my favourite tool for the job. It's a Swiss Army knife when it comes to output control (newer versions can output in JSON too):

   $ findmnt /
   TARGET SOURCE    FSTYPE OPTIONS
   /      /dev/sda1 ext4   rw,relatime,errors=remount-ro,data=ordered
   $ findmnt / -no source
   /dev/sda1
   $ findmnt / --json
   {
      "filesystems": [
         {"target": "/", "source": "/dev/sda1", "fstype": "ext4", "options": "rw,relatime,errors=remount-ro,data=ordered"}
      ]
   }
   $ findmnt / --df
   SOURCE    FSTYPE  SIZE  USED AVAIL USE% TARGET
   /dev/sda1 ext4   40.2G 25.8G 12.5G  64% /
   

findmnt is the tool to use:

findmnt will list all mounted filesytems or search for a filesystem. The findmnt command is able to search in /etc/fstab, /etc/fstab.d, /etc/mtab or /proc/self/mountinfo. If device or mountpoint is not given, all filesystems are shown.

The command prints all mounted filesystems in the tree-like format by default.

If it's an iPod, it will probably be mounted by gvfs.

Have a look in /run/user/1000/gvfs/afc* (assuming your uid is 1000)

The other command that might help is gvfs-mount -l