My Calibre Library complete disappeared... any help?

[DoodleBird]

I am quite new to Calibre, I started using it two or three weeks ago. I created my library and began adding books to it one by one (because my current/previous library is a mess). Today I open Calibre and am welcomed with a message about being unable to locate my Calibre Library file/database.

Okay, good thing I remember where I saved it. Nope, it's gone, like it vanished. I checked the trash just in case, not there.

So the thing is I had the library saved on an external hard drive (to access between computers), my hard drive is password locked and it locks automatically when the laptop sleeps, so I get this message when I open the Calibre and forget to unlock the drive first. But each time it was a simple matter of pointing Calibre back to the library folder. So how could my entire Calibre Library just disappear like this?

Note: I did back up all of the books, so it isn't a question about retrieving the book files, but rather how to get the library database back and maybe why it suddenly vanished in the first place. No one else has access to my hard drive so it isn't like some one got on here and accidentally deleted something.

Thanks for any help, it is much appreciated

[DoodleBird]

EDIT: I should also note that I run calibre both from Windows 10 and Mac OS X (El Capitan) and that I did a search of the entire hard drive for "Calibre Library" and that came up negative. So it didn't accidentally get moved.

[BetterRed]

@DoodleBird - search for 'metadata.db', that's the calibre library data base, its presence in a folder is what defines the folder as calibre library.

I'm suspicious of accessing the same library from Windows and OS/X, especially if you do it concurrently. Calibre is a single user system.

BR

[theducks]

As BR pointed out: presence of metadata.db is the defining aspect of a Calibre Library. Not the name.

The containing folder is the Library NAME. It can be almost anything ALL the file systems consider a legal name

If Calibre starts and can not FIND the current (last used) library, it pops a warning and will create a default, named 'Calibre Library'

You mention 2 OS... Dual Boot??
Calibre is NOT NAS/Cloud safe. Local drive only.

Do read the FAQ at calibre-ebook.com (where you get Calibre)

[DoodleBird]

As BR pointed out: presence of metadata.db is the defining aspect of a Calibre Library. Not the name.

The containing folder is the Library NAME. It can be almost anything ALL the file systems consider a legal name

Thank you for that clarification, but the only one that exists anywhere on my computer is the one that Calibre created AFTER telling me that it can't find my library (saved in a different location than the first, since my first one was named with the default "Calibre Library" name).

You mention 2 OS... Dual Boot??
Calibre is NOT NAS/Cloud safe. Local drive only.

Yes I dual boot. And yes I did skim through the FAQ section, but I did not read the section about storing the library on a networked drive (thus I did not see the part about it being a single user system and not working well between OSes, so thank you guys for pointing that out to me)

Well so if I cannot use Calibre between my OSx and windows boots, is there another program that can? Any suggestions? Or should I just keep my ebooks in some logically sorted system in my files?

[theducks]

Originally Posted by DoodleBird

Thank you for that clarification, but the only one that exists anywhere on my computer is the one that Calibre created AFTER telling me that it can't find my library (saved in a different location than the first, since my first one was named with the default "Calibre Library" name).



Yes I dual boot. And yes I did skim through the FAQ section, but I did not read the section about storing the library on a networked drive (thus I did not see the part about it being a single user system and not working well between OSes, so thank you guys for pointing that out to me)

Well so if I cannot use Calibre between my OSx and windows boots, is there another program that can? Any suggestions? Or should I just keep my ebooks in some logically sorted system in my files?

Dual boot can cause filename CASE issues, not TOTAL loss of library. The books are there, you just can't get at them (from Calibre UI) if the now have the wrong case.
OTOH NAS/networked drives can insert timing issues. Calibre does a set of tasks (more like a 'Transaction', but the undelayment does not support true 'Transactions' w/rollback)

Cloud just fight and need to be suspended for the duration of a Calibre session (and given time to mirror afrer stopping Calibre.

[fidvo]

I can't help you with retrieving your existing library, but I can confirm that you CAN run Calibre on the same library from multiple OS's, if you're careful. I have my library on an encrypted external hard drive, and although I can't speak for OSX, I run it from Linux and Windows, and I've only run into problems when I was doing something foolish, like peeking in the library folder. (Don't do this)

If you run the Check Library utility periodically, it can warn you of any issues that you need to correct. Keeping a backup of your books is a good idea too.

Calibre will never delete your library on its own. If the library no longer exists, something external to Calibre caused the problem.

[eschwartz]

As fidvo said, it is potentially risky but not guaranteed to cause danger.

The most likely source of problems is having a folder or file renamed on Windows, which is case-insensitive (but case-preserving)... and then the database believes the file is named one thing when it is really something else.
Windows doesn't care, but linux will be unable to find the file.

...

I have never had problems reading a Linux-created library on a Windows computer, but I have gotten Check Library ==>Missing/Extra formats when going the other way.

It is easy to fix if it happens, just do a Restore Database.

...

No idea what happened to your current library though, sorry.

If your backup includes the folder structure used by calibre, you can use Restore Database to rebuild the library based on the contents of the backup files.
Alternatively, if it was created with Save-to-Disk then you can Add Books from directories and it will import each folder as a book record --deriving metadata from the metadata.opf

[Divingduck]

I sometimes don't remember the exact directory name of a calibre library and tools like won't help too
Maybe it's worth to search for metadata.db instead of a directory name.

[DoodleBird]

Well, I have given up on finding my library and probably I will never know exactly what happened to it. It doesn't make sense to me. At least not that it would completely disappear like that. Very peculiar. Anyhow, at least I didn't lose all the books. Is it a good idea to keep a back up of the database file? Or should I just be more careful not to somehow ruin the database file or the library folder in any way?

[eschwartz]

It is a good idea to keep a backup of the entire library, including the database.

You can just point your favorite Cloud Storage client, e.g. Dropbox, at your calibre library and have it sync.
Although to be safe, you should always pause the Dropbox/other client while calibre is running, or the two programs might end up fighting over who gets to save the latest copy of the file -- which would be bad.

[theducks]

Originally Posted by DoodleBird

Well, I have given up on finding my library and probably I will never know exactly what happened to it. It doesn't make sense to me. At least not that it would completely disappear like that. Very peculiar. Anyhow, at least I didn't lose all the books. Is it a good idea to keep a back up of the database file? Or should I just be more careful not to somehow ruin the database file or the library folder in any way?

The database (db) file MUST match the contents of the Library Folder.
As eschwartz said: BACKUP the whole folder.

Better yet: Use Export/Import All Calibre data. (On the Library Icon). This backs up your USER settings, as well as the Library (books & metadata).

[BetterRed]

Originally Posted by theducks

Better yet: Use Export/Import All Calibre data. (On the Library Icon). This backs up your USER settings, as well as the Library (books & metadata).

Has Kovid committed to maintaining backwards compatibility to his export/import file format over time, i.e. will an export done today be importable into the future - let's say even just 2 years hence.

Library export copies every thing, every time. This can take considerable time for large libraries, even more so if one is exporting it over 'Net, in which case one must also consider the risk of losing the connection when exporting or importing. And if it takes long time, it's London to brick on, it won't get done as often as it ought be done.

Can one easily restore an individual book from a calibre export file? AFAIK the answer is no.

I recommend buying a good quality external HDD, preferable USB 3.0, probably 2-3TB. And use something like SyncBack, SyncToy, FreeFileSync, GoodSync . . . to maintain an incremental mirror image of all your valuable data including calibre libraries and its configuration folder. An incremental backup only copies changes since last time it was run, and a 'mirror' is an exact copy of the original and it can be used just like the original. And individual items can be restored - eg a cover.jpg that disappeared.

BR

[kovidgoyal]

Originally Posted by BetterRed

Has Kovid committed to maintaining backwards compatibility to his export/import file format over time, i.e. will an export done today be importable into the future - let's say even just 2 years hence.

Yes an export from calibre version x will always be importable from calibre version y > x

Just as a library folder from calibre version x is always useable from calibre version y > x -- and this has been so since the very earliest calibre days (approximately a decade and counting)

[BetterRed]

Originally Posted by kovidgoyal

Yes an export from calibre version x will always be importable from calibre version y > x

Just as a library folder from calibre version x is always useable from calibre version y > x -- and this has been so since the very earliest calibre days (approximately a decade and counting)

Fair enough - any plans to make it incremental; allow selective restore; provide a standalone 'unpack' utility ?

BR