grub-mkrescue: info: copying `/tmp/grub.8QTw3T/efi/boot/bootx64.efi' -> `/tmp/grub.eJwdh5/System/Library/CoreServices/boot.efi'.
grub-mkrescue: info: executing mformat -C -f 2880 -L 16 -i /tmp/grub.eJwdh5/efi.img ::.
grub-mkrescue: info: executing mcopy -s -i /tmp/grub.eJwdh5/efi.img /tmp/grub.8QTw3T/efi ::/.
grub-mkrescue: info: executing xorriso -as mkisofs -graft-points --modification-date=2017050208103400 -hfsplus -apm-block-size 2048 -hfsplus-file-creator-type chrp tbxj /System/Library/CoreServices/.disk_label -hfs-bless-by i /System/Library/CoreServices/boot.efi --efi-boot efi.img -efi-boot-part --efi-boot-image --protective-msdos-label -o /home/e/boot.iso -r /tmp/grub.eJwdh5 --sort-weight 0 / --sort-weight 1 /boot /home/e/iso.
e@e:~$ ls boot.iso
ls: cannot access 'boot.iso': No such file or directory
e@e:~$ sudo updatedb
e@e:~$ locate boot.iso
e@e:~$