How can I replace my home directory without coorupting my system? - linux

Question

After setting up my Raspberry Pi, I made an image to make reverting to older software states easier. Recently I wanted to do that so I saved the content of my /home/pi folder, formated the sd-card and wrote the image onto it.
So far everything worked fine. Then I tried to simply delete the complete /home/pi folder and replace it with my previously saved folder from the old image. Now it seems like all files are there. But it doesnt boot correctly.
At some point it just stops to boot. I can then use it normally like the terminal, but Desktop is not starting.
So, how can I replace my home directory the right way so I don't make any damage to the system?
edit:
I just tried to do this again.
sudo cp -a /home/pi/fileserver/backup /home/backup
(i mounted a network drive in fileserver. Since network is on windows i assume all permissions are already gone here)
cp -a /home/pi/. /home/original
sudo umount /home/pi/fileserver
rm -r /home/pi/
mv /home/backup /home/pi
sudo chmod -R 755 /home/pi (So far everything still works)
sudo reboot
After reboot it doesnt boot correctly anymore. When I wait long enough I see errors of X Server.

Answer 1

That's quite doubtful approach to archiving the data. First of all, as you mentioned, windows will remove the permission bits. Running chmod -R 755 afterwards has very bad consequences because some programs in order to work require very specific access bits on some files (ssh keys for example). Not to mention that making everything executable is bad for security.
Considering your scenario, you may either
a) backup everything into Tar or Zip archives - this way permissions will be intact
b) Make virtual disk file which will be stored on shared windows drive and mounted to /home/pi
How to do scenario A:
cd /home/pi
tar cvpzf backup.tar.gz .
Copy backup.tar.gz to shared drive
to unpack:
cd /home/pi
tar xpvzf backup.tar.gz
Pros:
One-line backup
Takes small amount of space
Cons:
Packing/unpacking takes time
How to do scenario B:
1) Create a new file to hold the virtual drive volume:
cd /mnt/YourNetworkDriveMountPoint
fallocate -l 500M HomePi.img
dd if=/dev/zero of=HomePi.img bs=1M count=500
mkfs -t ext3 HomePi.img
2) Mount it to home dir
mount -t auto -o loop HomePi.img /home/pi/
500 means the disk will be 500 megabytes in size
This way your whole pi will be saved as a file on windows shared drive, but all the content will be in ext3 so all permissions are preserved.
I suggest you though to keep the current version image file on Pi device itself and the old versions on shared drive. Just copy files over if you need to switch because otherwise if all images are on shared drive then read/write performance will be 100% dependant on network speed.
You can then easily make copies of this file and swap them instantly by unmounting existing image and mounting new one
Pros:
Easy swap between backup versions
Completely transparent process
Cons:
If current image file is on shared drive, performance will be reduced
It will consume considerably more space because all 500 megs will be preallocated.
Pi user must be logged off during image swap for obvious reasons
Now, as for issues with Desktop not displayed, you need to check /var/log/Xorg.0.log for detailed messages. Likely this is caused by messed permissions. I would try to rename/remove your current Xorg settings and cache which are located somewhere in /home/Pi/.config/ (depends on what you're using - XFCE, Gnome, etc.) and let X server recreate them. But again, before doing this please check Xorg.0.log for exact messages - maybe there's another error. If you need any further help please comment to this answer