UPDATE 05/13: I ran simultaneous backups from 3 workstations (3 different Samba users) yesterday (Windows image backups - almost 47 GB the biggest file, .vhdx type). I noticed that 1 Samba users wrote down files as "read only" mode while the others 2 Samba users wrote down normal files, for normal I mean "read write" mode files. This exercise showed me the following: a) big files DISTINCT from .zip type are not issues; b) at least 1 Samba user is writing down files as "read only" mode. So far, the event responsible for automatically changing the NAS partition to "read only" filesystem is triggered when very big .zip files are created or copied FROM terminal source on LAN directly to NAS server external USB drive.

Thanks everyone in advanced for caring and helping. Suddenly, during backups from Windows Server 2008 R2 (via 7-Zip), destination NAS hard drive is getting changed automatically to "read only" mode - it seems that it happens while creation of very large .zip files (around 50 GB or larger). It is not due to lack of space, that's for sure (currently 2 TB free out of 3.58 TB), and also Samba shares has no size limitation for users (regarding User Quotas). This is the environment:

  • OS: Ubuntu Server 18.04
  • USB Device (according to smartctl): Vendor: WD Product: My Book 25EE Revision: 4007 Compliance: SPC-4 User Capacity: 4,000,786,153,472 bytes [4.00 TB] Logical block size: 512 bytes Physical block size: 4096 bytes LU is fully provisioned Rotation Rate: 5400 rpm Form Factor: 3.5 inches Logical Unit id: 0x50014ee2660fd2e6 Serial number: WCC7K2FKNZHD Device type: disk Local Time is: Tue May 10 10:00:43 2022 -03 SMART support is: Unavailable - device lacks SMART capability.

=== START OF READ SMART DATA SECTION === Current Drive Temperature: 0 C Drive Trip Temperature: 0 C

Error Counter logging not supported

No self-tests have been logged

  • Mountpoint info: /dev/sdb1 on /mnt/backup type ext4 (rw,nosuid,nodev,noexec,relatime,quota,usrquota,grpquota,data=ordered,user)

I'm a very Linux enthusiast but I'm far from being a system administrator, so please if you guys would like me to print some log content just handle to me the command line to get it.

  • where do you see it being changed to read only?
    – Esther
    May 10, 2022 at 14:05
  • When checking the backup data later, I noticed that zip files created during a specific backup session are 0760 mode "read only" and the entire NAS partition becomes "read-only" filesystem > /mnt/backup type ext4 (ro,nosuid,nodev,noexec,relatime,quota,usrquota,grpquota,data=ordered,user).
    – Jose M
    May 10, 2022 at 16:10
  • so the backups are read-only, but the rest of the filesystem is normal, is that correct? are you sure this isn't intended behavior?
    – Esther
    May 10, 2022 at 16:15
  • It isn't intended behavior. Backups were running correctly for at least 2 years. Just by chance this all issue (I mean the automatically switching to "read-only" mode partition and files) started after using "timedatectl" command in the backup server to update time / date settings AND also when a specific Zip backup data file reached a huge size (more than 40 GB).
    – Jose M
    May 10, 2022 at 16:48
  • did you change the time when you ran timedatectl? that might cause problems
    – Esther
    May 10, 2022 at 16:50

2 Answers 2


(Sorry, I can't comment yet.)

Please post the output of dumpe2fs -h /dev/sdb1 |grep Errors. My guess is it is set to "remount-ro". About what causes such an error in the first place, the most common causes are:

  • the filesystem has errors, probably from power loss/reset at the wrong time, and fsck couldn't repair this from the journal alone; you'll need to manually run fsck on the unmounted filesystem
  • your harddrive is about to die
  • your cable is bad
  • there is a WD Red with SMR in your MyBook, and it sometimes takes so long to write out the data that timeouts are exceeded and the write is considered as failed

Any of these will trigger the "remount-ro" sooner or later.

  • Thanks for replaying! Output requested: dumpe2fs 1.44.1 (24-Mar-2018) Errors behavior: Continue
    – Jose M
    May 10, 2022 at 18:37
  • Please, clarify if file size could be an issue so I can analyze alternative solutions to that.
    – Jose M
    May 11, 2022 at 15:28
  • It shouldn't be an issue. Maybe just a side effect of having steady writes over a long time. So you will have to check the syslog for the actual errors that led to the fs being remounted.
    – mow
    May 24, 2022 at 17:53

Well. I would like to thank everyone who might have collaborated somehow. It looks like the WD external HD went finally damaged since it cannot be used by any OS, I mean the device is detected as USB device and even Linux logs what kind of device it is, manufacturer, name and model of the product BUT it isn't able to use it; similar happens on Windows.

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