hi Devel,
there are no duplicate lines in fstab.
The output of blkid are matching with the content of fstab. The UUIDs have i compared with the output of gparted, They are identical.
the file fstab has the following content :
/dev/sda2 none swap sw 0 0
/dev/sda3 /media/disk1part3 ext4 noauto, users, rw, exec, relatime 0 0
/dev/sda4 /media/disk1part4 ext4 noauto, users, rw exec, relatime 0 0
/dev/sdb4 /media/disk2part4 ext3 noauto, users, rw, exec, realtime 0 0