Hum I'm definetly not a linux expert, so I don't get how df can show /boot on /dev/sda1, but that in fact it is on /dev/sda 
Anyway perhaps the fstab could help :
# This file is edited by fstab-sync - see 'man fstab-sync' for details
/dev/vg0/root / ext3 defaults 1 1
LABEL=/boot /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /dev/shm tmpfs defaults 0 0
/dev/vg0/home /home ext3 defaults 1 2
/dev/vg0/logi /logiciels ext3 defaults 1 2
/dev/vg0/opt /opt ext3 defaults 1 2
none /proc proc defaults 0 0
none /sys sysfs defaults 0 0
/dev/vg0/tmp /tmp ext3 defaults 1 2
/dev/vg0/usr /usr ext3 defaults 1 2
/dev/vg0/var /var ext3 defaults 1 2
LABEL=SWAP-sda3 swap swap defaults 0 0
/dev/vg0/extr /usr/extraclients ext3 suid,dev,noexec 0 0
/dev/vg0/sftp /usr/extraclients/sftp ext3 suid,dev,ro,exec 0 0
/dev/vg0/sauv /home/d/sauve ext3 suid,dev,exec 0 0
hostname.domain:/u/c/cft/domain /u/c/cft/domain nfs suid,dev,exec,noauto 0 0