Macで、Debianインストール用のCDイメージをUSBメモリに書き込みました。そのときの作業ログです。
iMac:~ $ diskutil list
/dev/disk0
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *500.1 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_HFS Macintosh HD 499.2 GB disk0s2
3: Apple_Boot Recovery HD 650.0 MB disk0s3
/dev/disk3
#: TYPE NAME SIZE IDENTIFIER
0: FDisk_partition_scheme *4.0 GB disk3
1: DOS_FAT_32 4.0 GB disk3s1
iMac:~ ishidate$ mount
/dev/disk0s2 on / (hfs, local, journaled)
devfs on /dev (devfs, local, nobrowse)
map -hosts on /net (autofs, nosuid, automounted, nobrowse)
map auto_home on /home (autofs, automounted, nobrowse)
/dev/disk3s1 on /Volumes/Untitled (msdos, local, nodev, nosuid, noowners)
iMac:~ ishidate$ sudo dd if=debian-8.0.0-i386-netinst.iso of=/dev/disk3
Password:
dd: /dev/disk3: Resource busy
iMac:~ ishidate$ sudo umount /Volumes/Untitled
umount(/Volumes/Untitled): Resource busy -- try 'diskutil unmount'
iMac:~ ishidate$ diskutil umount /Volumes/Untitled
Volume (null) on disk3s1 unmounted
iMac:~ ishidate$ sudo dd if=debian-8.0.0-i386-netinst.iso of=/dev/disk3
645120+0 records in
645120+0 records out
330301440 bytes transferred in 1325.887596 secs (249117 bytes/sec)
iMac:~ ishidate$