On Linux or OSX I use
dd to make a backup from SD card. Reverse
of (i.e. to where they point - source and destination) afterwards to restore, but be careful not to restore to a wrong disk. It will be destroyed without a warning!!!
fdisk to get the device id of you SD card (check the size)
then I use dd to make a diskimage (change /dev/sdb with what you found with fdisk -l):
dd bs=4M if=/dev/sdb of=image1-`date +%d%m%y`.img
or this to make a compressed imag:
dd bs=4M if=/dev/sdb | gzip > image1-`date +%d%m%y`.img.gz
on OSX find device with:
dd with something like
if=/dev/rdisk1 (the '
rdisk1 stands for raw which is faster)
On OSX you can also use 'Disk Utility'
by making a crontab like this it will give you a status every minute:
* * * * * /usr/bin/pkill -USR1 -x dd