Yes, you perform this command on the shell. Do it on any ext3 filesystem on your machine. The /dev/sda1 was just an example.
# tune2fs -c 0 /dev/sda1
# tune2fs -c 0 /dev/sda2
# tune2fs -c 0 /dev/sda3 ... and so on.
The tune2fs does not cause data loss. If you want to feel safe, unmount the filesystem first and then do the tune2fs.
The filesystem has a superblock. In it, there is the filesystem state, last time it was mounted, etc. When the system is running there is data that the kernel must write from cache to the filesystem. When the system reboots by accident, the journal helps recover the filesystem to a consistent state for normal operation. Journaling is therefore a safety net against fileystem corruption. If you turn off the fielsystem check feature, you're taking chances that one day your filesystem will get corrupted and your data loss will not make you happy.
I encourage you to read the man pages.
http://linux.die.net/man/8/tune2fsWARNING: Removing an external journal from a filesystem which was not cleanly unmounted without first replaying the external journal can result in severe data loss and filesystem corruption.
You have been warned.
