upgrade
I just upgraded my ubuntu lucid to natty , during the upgrade it replaced most of the
running applications with a newer version.
How does this work? (Won't the applications crash?)
What will happen to the application if a lib file got upgraded and a running application which is looking for a older lib tries to load it?
From my experience I would assume that while packages and modules are running they are held in memory and don't refer back to their copy on the hard drive much. You can see this if you run a program in ubuntu and then remove the related packages while its running. It will keep running, but if you close it, you can't restart it.
I would assume the same happens with a distribution upgrade. All of the packages related to the original version of ubuntu are still running even though they have been removed and replace with the new ones, so when they are finally stopped on a system restart, the new packages take over.
There is a tool called Y-PPA-Manager that lets you do exactly that.
To try Y-PPA-Manager, you need to run the following commands in a terminal:
sudo add-apt-repository ppa:webupd8team/y-ppa-manager
sudo apt-get update
sudo apt-get install y-ppa-manager
After installing, run the software and click on 'Advanced' button.
After clicking on that button, you would come up with a window similar to the one below. Click on 'Re-enable working PPAs after Ubuntu upgrade'.
You would then be prompted for your password. Enter your password and click OK. After that, you would get a dialog box like this:
Click OK and wait till all the working PPAs are re-enabled. When the entire process is successfully completed, you would be notified.
Best Answer
Linux (and other UNIXes) draws a distinction between the name of a file (the link), the file itself (often identified with the inode), and open handles to the file. When you go to delete a file, you call the
unlink()call - this erases the link to the file (you could also userename()to overwrite it with a different inode). However, if open handles to the file (or other links - files can have multiple hardlinks) remain, the inode remains, and so does the file content, until all links and handles go away.So running programs using the library or whatever keep a handle to the old version (often implicitly through a memory mapping), so it stays on disk. It just doesn't have a filename anymore, and will be cleaned up when all programs using it shut down (or on the next reboot, during the filesystem check or journal replay).
Further, note that programs expecting the 'old library' will do just fine with newer versions of the library. Linux libraries are assigned a filename ('soname') that reflects the version of the ABI (Application Binary Interface) offered by the library. For example, the C library on my system is
libc.so.6. Any program compiled against an older version of libc, but still a version of libc implementing the version 6 ABI, will work fine with it. Really old programs will look for alibc.so.5orlibc.so.4or something instead; in this case, you'd need to keep the old version around as well - but since the filename is different, this isn't a problem.