5GB are not enough for the root partition you have allocated for a VM? No problem! Lets fix it.
You need to run all commands with root permissions and you need to change vm_image.qcow2 and /dev/vda to values that match your system.
# all command need to be run as root
# resize the image (host)
qemu-img resize vm_image.qcow2 +10G
# rewrite partion (client)
fdisk /dev/vda
# in fdisk
# - delete partition
# - recreate partition it with same stating position
# - write
# reboot (client)
reboot
# grow filesystem (client) - requires online growing
resize2fs /dev/vda
Below you will find a sample fdisk run:
$ fdisk /dev/vda
Command (m for help): p
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 9437183 4717568 83 Linux
Command (m for help): d
Selected partition 1
Command (m for help): p
Device Boot Start End Blocks Id System
Command (m for help): n
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4, default 1): 1
First sector (2048-10485759, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-10485759, default 10485759):
Using default value 10485759
Command (m for help): p
Device Boot Start End Blocks Id System
/dev/vda1 2048 10485759 5241856 83 Linux
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.