How to resize root partition online :
1) [root@oel7 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/root_vg-root 5.0G 4.5G 548M 90% /
2)
PV /dev/sda2 VG root_vg lvm2 [6.00 GiB / 0 free]
as here it shows that there is no space left on root_vg volume group, so first i need to extend VG
3)
[root@oel7 ~]# vgextend root_vg /dev/sdb5
Volume group "root_vg" successfully extended
4)
[root@oel7 ~]# pvscan
PV /dev/sda2 VG root_vg lvm2 [6.00 GiB / 0 free]
PV /dev/sdb5 VG root_vg lvm2 [2.00 GiB / 2.00 GiB free]
5) Now extend the logical volume
[root@oel7 ~]# lvextend -L +1G /dev/root_vg/root
Size of logical volume root_vg/root changed from 5.00 GiB (1280 extents) to 6.00 GiB (1536 extents).
Logical volume root successfully resized
3) [root@oel7 ~]# resize2fs /dev/root_vg/root
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Bad magic number in super-block while trying to open /dev/root_vg /root
Couldn't find valid filesystem superblock.
as root partition is not a ext* partiton so , you resize2fs will not work for you.
4) to check the filesystem type of a partition
[root@oel7 ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/root_vg-root xfs 6.0G 4.5G 1.6G 75% /
devtmpfs devtmpfs 481M 0 481M 0% /dev
tmpfs tmpfs 491M 80K 491M 1% /dev/shm
tmpfs tmpfs 491M 7.1M 484M 2% /run
tmpfs tmpfs 491M 0 491M 0% /sys/fs /cgroup
/dev/mapper/data_vg-home xfs 3.5G 2.9G 620M 83% /home
/dev/sda1 xfs 497M 132M 365M 27% /boot
/dev/mapper/data_vg01-data_lv001 ext3 4.0G 2.4G 1.5G 62% /sybase
/dev/mapper/data_vg02-backup_lv01 ext3 4.0G 806M 3.0G 22% /backup
above command shows that root is an xfs filesystem , so we are sure that we need to use xfs_growfs command to resize the partition.
6) [root@oel7 ~]# xfs_growfs /dev/root_vg/root
meta-data=/dev/mapper/root_vg-root isize=256 agcount=4, agsize=327680 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0 finobt=0
data = bsize=4096 blocks=1310720, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=2560, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 1310720 to 1572864
[root@oel7 ~]# df -Th
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/root_vg-root xfs 6.0G 4.5G 1.6G 75% /