How to vgscan in RHEL 5.8 rescue mode?

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http://unix.stackexchange.com – I want to increase the journaling size of an EXT3 FS: /var. I booted up a RHEL 5.8 DVD, and tried the "linux rescue" mode. The problem is that the original install that has the mentioned /var FS is in a vg/lvm. So I tried the command: vgscan as ex.: this howto states it: http://www.linuxtopia.org/online_books/rhel6/rhel_6_installation/rhel_6_... but the vgscan binary is not found. I tried to find it with "find / -name vgscan", but it didn't find it. Q: What am I missing? Isn't the rescue mode for RESCUING?? (HowTos)