To create a 1500MB linear LV named 'testlv' and its block device special '/dev/testvg/testlv':
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# lvcreate -L1500 -ntestlv testvg
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To create a 100 LE large logical volume with 2 stripes and stripe size 4 KB.
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# lvcreate -i2 -I4 -l100 -nanothertestlv testvg
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If you want to create an LV that uses the entire VG, use vgdisplay to find the "Total PE" size, then use that when running lvcreate.
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# vgdisplay testvg | grep "Total PE"
Total PE              10230
# lvcreate -l 10230 testvg -n mylv
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If you want the logical volume to be allocated from a specific physical volume in the volume group, specify the PV or PVs at the end of the lvcreate command line.
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# lvcreate -L 1500 -ntestlv testvg /dev/sdg
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