Simulate mounted volume errors to cause read only - linux

Question

Few days ago we have encountered an unexpected error where one of the mounted drive on our RedHat linux machine became Read-Only. The issue was cause by the network outage in the datacenter.
Now I need to see if I can reproduce the same behavior where drive will be re-mounted as Read-Only while application is running.
I tried to remounted it was read-only but that didn't work because there are files that are opened (logs being written).
Is there a way to temporary cause the read-only if I have root access to the machine (but no access to the hypervisor).
That volume is mounted via /etc/fstab. Here is the record:
UUID=abfe2bbb-a8b6-4ae0-b8da-727cc788838f / ext4 defaults 1 1
UUID=8c828be6-bf54-4fe6-b68a-eec863d80133 /opt/sunapp ext4 rw 0 2
Here are the output of few commands that shows details about our mounted drive. I can add more details as needed.
Output of fdisk -l
Disk /dev/vda: 268.4 GB, 268435456000 bytes, 524288000 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0008ba5f
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 524287966 262142959+ 83 Linux
Disk /dev/vdb: 42.9 GB, 42949672960 bytes, 83886080 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Output of lsblk command:
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
vda 253:0 0 80G 0 disk
└─vda1 253:1 0 80G 0 part /
vdb 253:16 0 250G 0 disk /opt/sunup
Output of blkid command:
/dev/vda1: UUID="abfe2bbb-a8b6-4ae0-b8da-727cc788838f" TYPE="ext4"
/dev/sr0: UUID="2017-11-13-13-33-07-00" LABEL="config-2" TYPE="iso9660"
/dev/vdb: UUID="8c828be6-bf54-4fe6-b68a-eec863d80133" TYPE="ext4"
Output of parted -l command:
Warning: Unable to open /dev/sr0 read-write (Read-only file system). /dev/sr0
has been opened read-only.
Error: /dev/sr0: unrecognised disk label
Model: QEMU QEMU DVD-ROM (scsi)
Disk /dev/sr0: 461kB
Sector size (logical/physical): 2048B/2048B
Partition Table: unknown
Disk Flags:
Model: Virtio Block Device (virtblk)
Disk /dev/vda: 268GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 268GB 268GB primary ext4 boot
Model: Virtio Block Device (virtblk)
Disk /dev/vdb: 42.9GB
Sector size (logical/physical): 512B/512B
Partition Table: loop
Disk Flags:
Number Start End Size File system Flags
1 0.00B 42.9GB 42.9GB ext4

Answer 1

Yes, you can do it. But the method proposed here may cause data loss, so use it only for testing.
Supposing you have /dev/vdb mounted as /opt/sunapp, do this:
First, unmount it. You may need to shut down any applications using it first.
Configure a loop device to mirror the contents of /dev/vdb:
losetup /dev/loop0 /dev/vdb
Then, mount /dev/loop0 instead of /dev/vdb:
mount /dev/loop0 /opt/sunapp -o rw,errors=remount-ro
Now, you can run your application. When it is time to make /opt/sunapp read-only, use this command:
blockdev --setro /dev/vdb
After that, attempts to write to /dev/loop0 will result in I/O errors. As soon as file system driver detects this, it will remount the file system as read-only.
To restore everything back, you will need to unmount /opt/sunapp, detach the loop device, and make /dev/vdb writable again:
umount /opt/sunapp
losetup -d /dev/loop0
blockdev --setrw /dev/vdb

Answer 2

When I had some issues like corrupted disks, I had used ntfsfix.
Please see if these commands, solve the problem.
sudo ntfsfix /dev/vda
sudo ntfsfix /dev/vdb