Storage and LVM
Linux/RHEL notes for disks, filesystems, mounts, /etc/fstab, and LVM.
Use this page when checking disk usage, mounted filesystems, block devices, filesystem UUIDs, or LVM layout.
Basic disk checks
Show disk usage
df -h
Shows mounted filesystems and how much space is used.
Useful when checking if a server or filesystem is full.
Show filesystem type
df -Th
Show folder size
du -sh /path/to/folder
Example:
du -sh /var/log
Show largest folders inside a path
sudo du -h --max-depth=1 /path | sort -h
Example:
sudo du -h --max-depth=1 /var | sort -h
Block devices
Show block devices
lsblk
Show filesystems with lsblk
lsblk -f
Show UUIDs
blkid
Show mounted filesystems
mount
Cleaner view:
findmnt
Show one mount point
findmnt /mount/point
Example:
findmnt /
Filesystem checks
Check filesystem type
df -T /mount/point
Example:
df -T /
Check disk/inode usage
df -h
df -i
df -i is useful when disk space is free but the system says no space is left. It may be out of inodes.
Show open deleted files
sudo lsof | grep deleted
This is useful when space is not freed after deleting large files. A process may still have the deleted file open.
Mounting
Mount a filesystem
sudo mount /mount/point
This works if the mount exists in /etc/fstab.
Mount a device manually
sudo mount /dev/DEVICE /mount/point
Example:
sudo mount /dev/sdb1 /mnt/data
Unmount a filesystem
sudo umount /mount/point
If it says the target is busy, check what is using it:
sudo lsof +f -- /mount/point
or:
sudo fuser -vm /mount/point
/etc/fstab
/etc/fstab controls filesystems that should mount automatically.
View fstab
cat /etc/fstab
Test fstab without rebooting
sudo mount -a
Be careful. If /etc/fstab is wrong, boot can be affected.
Example fstab line
UUID=xxxx-xxxx /mnt/data xfs defaults 0 0
Common fields:
device/UUID mountpoint filesystem options dump fsck
LVM basics
LVM means Logical Volume Manager.
Basic structure:
Physical Volume → Volume Group → Logical Volume → Filesystem → Mount point
PV → VG → LV → XFS/ext4 → /data
Physical volumes
Show physical volumes
sudo pvs
More detail:
sudo pvdisplay
Volume groups
Show volume groups
sudo vgs
More detail:
sudo vgdisplay
Logical volumes
Show logical volumes
sudo lvs
More detail:
sudo lvdisplay
Show LVM tree
lsblk
Useful because it shows the relation between disk, partition, LVM, and mount point.
Extend LVM filesystem
Basic flow:
1. Check current disk/filesystem
2. Check free space in VG
3. Extend LV
4. Grow filesystem
5. Verify
Check current size
df -h
lsblk
sudo lvs
sudo vgs
Extend logical volume
Example: add 10 GB:
sudo lvextend -L +10G /dev/VG_NAME/LV_NAME
Example: use all free space in the VG:
sudo lvextend -l +100%FREE /dev/VG_NAME/LV_NAME
Grow XFS filesystem
RHEL commonly uses XFS.
sudo xfs_growfs /mount/point
Example:
sudo xfs_growfs /
Grow ext4 filesystem
sudo resize2fs /dev/VG_NAME/LV_NAME
One-command LV extend and filesystem grow
Sometimes this works:
sudo lvextend -r -L +10G /dev/VG_NAME/LV_NAME
The -r option attempts to resize the filesystem too.
Still verify after:
df -h
sudo lvs
Dangerous storage actions
Be very careful with:
mkfs
fdisk
parted
wipefs
lvremove
vgremove
pvremove
dd
umount on production filesystems
editing /etc/fstab
These can destroy data or break boot/mounts.
First commands for disk issues
hostnamectl
df -h
df -i
lsblk
lsblk -f
findmnt
sudo pvs
sudo vgs
sudo lvs
sudo du -h --max-depth=1 /var | sort -h
sudo lsof | grep deleted
Disk full troubleshooting flow
1. Which filesystem is full?
2. Is it disk space or inodes?
3. Which directory is growing?
4. Are logs too large?
5. Are deleted files still open?
6. Is it safe to remove/compress/archive files?
7. Is LVM free space available?
8. Does the filesystem need to be extended?
Safe notes
Do not paste real production disk names or customer paths if they reveal sensitive systems.
Use generic examples like:
/dev/sdb1
/dev/vg_data/lv_app
/mnt/data
/server01
Personal notes
Add work-specific storage lessons here over time.