All my pictures have disappeared without my deleting them. I use a Sony Vaio laptop with Ubuntu 14.04.
Where are my pictures?
If all else fails try photorec
the 'testdisk' package. (available in the universe software repositories).
you can see if you already have it with the command which photorec
which will return the installation path if it's installed.
If not, insure that the universe repository is active by checking the box in software and updates.
What you will need:
1) the drive that contained your missing pictures (this may be obvious but you should not write to this drive until you have attempted recovery as you may overwrite the very data you are trying to recover resulting in further data loss).
2) another drive with sufficient space for your recovered pictures.
3) a live Ubuntu disk or flash drive to boot from (I recommend using an LTS version for this as they are more stable) currently 12.04 or 14.04
4) an active internet connection
5) the ability to read and understand all the steps and options prior to beginning.
Step 1 Boot from the live media described in item 3 with the source (item 1) and target (item 2) drives attached.
Step 2 insure your internet connection is up and running by whatever means you are most comfortable (ping google.com or go there with your browser or whatever)
Step 3
Open a terminal and install photorec with sudo apt-get testdisk
Step 4
Identify your source and target drives with the command sudo fdisk -l
you should get output similar to the below and should be able to identify your source and target drives from the differences in the output.
Step 5
If your target drive is new and unused partition it and format it with gparted.
If your target drive already contains a filesystem with needed data skip step 5 (you have been warned)
Step 6 mount the target partition that you have enough space for your pictures. for example sudo mount /dev/sdb1 /mnt
(insure /dev/sdb1 is your target, change as necessary to your environment)
Step 7 start photorec by issuing the command sudo photorec
Step 8 adjust options as necessary to enable brute force recovery or deal with low memory, etc as you see fit. Also adjust FileOpt if desired to recover the types of files you are looking for and skip those you aren't. (the default selection recovers many types of files you aren't seeking).
Step 9 use the up down arrow keys to select the partition (or whole disk) you wish to recover data from and the right left keys to highlight search and hit enter. Choose the filesystem type the files were stored on from the choices available, then choose to search either the free space (if you think you deleted them or the entire disk if you have no clue what happened)
Step 10
Highlight the target directory and hit Enter then hit C
Recovery will begin - when complete you should see something similar to this:
PhotoRec is file data recovery software designed to recover lost
files including video, documents and archives from Hard Disks and CDRom
and lost pictures (Photo Recovery) from digital camera memory. PhotoRec
ignores the filesystem and goes after the underlying data, so it'll
work even if your media's filesystem is severely damaged or formatted.
PhotoRec is safe to use, it will never attempt to write to the drive or
memory support you are about to recover lost data from.
If something is unclear, drop me a comment with what exactly you didn't understand and I'll try to elaborate.
Sources: experience, man page
ls -a
to see if somehow they became hidden, normally files don't disappear on their own unless you did something.