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# Tested on RHEL 5, 6 & 7
# *** It is not possible to reduce an xfs filesystem so this recipe is valid only for # ext2/ext3/ext4 filesystems. # *** As of February 2016, new implementation of LVM didn't permit reducing a RAID volume: # "Unable to reduce RAID LV - operation not implemented." # Just in case, I recommended to backup up all important data before reducing a F.S. MNTPT=/testmntpt SIZE=128M # Final size, in Mbytes. Without "M" to specify size in Bytes. VG=`mount | awk '{if ( $3 == "'$MNTPT'" ) print$1}' | cut -f4 -d'/' | cut -f1 -d '-'` LV=`mount | awk '{if ( $3 == "'$MNTPT'" ) print$1}' | cut -f4 -d'/' | cut -f2 -d '-'` df -h $MNTPT Filesystem Size Used Avail Use% Mounted on /dev/mapper/testvg-testlv 788M 17M 731M 3% /testmntpt testlv testvg mwi-aom-- 800.00m testlv_mlog 100.00 umount $MNTPT # First, we check the file system. 'e2fsck' is used to check the ext2/ext3/ext4 family of # file systems. '-f' option force checking even if the file system seems clean. This step # is mandatory.
e2fsck -f /dev/$VG/$LV e2fsck 1.39 (29-May-2006) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/testvg/testlv: 11/102592 files (9.1% non-contiguous), 7532/204800 blocks # Then, we reduce the size of the filesystem
resize2fs -p /dev/$VG/$LV $SIZE resize2fs 1.39 (29-May-2006) Resizing the filesystem on /dev/testvg/testlv to 32768 (4k) blocks. Begin pass 3 (max = 7) Scanning inode table XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX The filesystem on /dev/testvg/testlv is now 32768 blocks long. # And finally, we reduce the size of the logical volume lvreduce -L $SIZE /dev/$VG/$LV WARNING: Reducing active logical volume to 128.00 MB THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce testlv? [y/n]: y Reducing logical volume testlv to 128.00 MB Logical volume testlv successfully resized lvs | grep $LV testlv testvg mwi-ao 128.00M testlv_mlog 100.00 mount /dev/$VG/$LV $MNTPT df -h $MNTPT Filesystem Size Used Avail Use% Mounted on /dev/mapper/testvg-testlv 127M 17M 104M 14% /testmntpt |