I have an debian virtual machine and suddenly I’m seeing that message.

That means, we are running out of disk. To solve it we need to increase the disk maximum size, resize it and refresh the LVM

1.- Maximum disk size and resize

2.- Modify the LVM

This is just a copy paste from a guy who did it better. Notice the SUDO !:

Step:1 Type ‘ df -h’ command to list the file system
Run the “df -h” command followed by the file system to view total ,used and available disk space. Notice the 100% usage.

[root@cloud home]# df -h /home/
 Filesystem            Size  Used Avail Use% Mounted on
                       9.7G  9.2G     0 100% /home

Step:2 Now check whether free space is available space in the volume group
To display volume group details, execute the vgdisplay command followed by volume group name,

vgdisplay < Volume-Group-Name>

[root@cloud home]# vgdisplay vg_cloud
   --- Volume group ---
 VG Name                      vg_cloud
 System ID
 Format                       lvm2
 Metadata Areas               1
 Metadata Sequence No         4
 VG Access                    read/write
 VG Status                    resizable
 MAX LV                       0
 Cur LV                       3
 Open LV                      3
 Max PV                       0
 Cur PV                       1
 Act PV                       1
 VG Size                      27.01 GiB
 PE Size                      4.00 MiB
 Total PE                     6915
 Alloc PE / Size              5256 / 20.53 GiB
 Free  PE / Size              1659 / 6.48 GiB
 VG UUID                      1R89GB-mIP2-7Hgu-zEVR-5H02-7GdB-Ufj7R4

Step:3 Use lvextend command to increase the size.
Run below lvextend command to extend the file system,

the command will extend the file system size by 2GB. You can also specify the size in MB , just replace G with M.

[root@cloud ~]# lvextend -L +2G /dev/mapper/vg_cloud-LogVol00
Extending logical volume LogVol00 to 11.77 GiB
Logical volume LogVol00 successfully resized

Step:3 Run the resize2fs command

In above step we have executed the lvextend command to extend the file system size by 2 GB but still the file system is not updated, so execute the following resize2fs command

[root@cloud ~]# resize2fs /dev/mapper/vg_cloud-LogVol00

To verify the changes:

[root@cloud ~]# df -h /home/
 Filesystem            Size  Used Avail Use% Mounted on
                        12G  9.2G  1.9G  84% /home

If there is any error like (read only file system)…

Since things were working previously with the disk specified as /dev/vda1 instead of via UUID, I thought I’d just edit the fstab file and be done with it:

sudo nano /etc/fstab

We need to remount the disk

mount -o remount,rw /dev/vda1 /

After that and a reboot, the disk should be read-write.

Sources: https://www.youtube.com/watch?v=Fteij2amMos