Changes

First, we [[dumping files|get the files]] from the target process via unix socket. Then for each of them get the file's name via /proc by calling <code>readlink</code> on the /proc/self/fd/$fd path. It's important to note, that we readlink ''self'' FD to get the file's name we can work with. Next we <code>fstat()</code> the respective self file descriptor.

First, we [[dumping files|get the files]] from the target process via unix socket. Then for each of them get the file's name via /proc by calling <code>readlink</code> on the /proc/self/fd/$fd path. It's important to note, that we readlink ''self'' FD to get the file's name we can work with. Next we <code>fstat()</code> the respective self file descriptor.

If the <code>st_nlink</code> field is zero, then the file is fully deleted from the system. Since no filesystems allow to create a name back for such files, we have no other choice other than get the file itself into images. So we generate a so called ''ghost file'' in the image directory and copy the file contents into it.

If the <code>st_nlink</code> field is zero, then the file is fully deleted from the system. Since no filesystems allow to create a name back for such files, we have no other choice other than get the file itself into images. So we generate a so called ''ghost file'' in the image directory and copy the file contents into it. Since the file is taken into the images, it would be good if the file size is not huge. By default CRIU dumps ghost files at most 1Mb in size. But with the option <code>--ghost-limit</code> this limit can be changed.

But what happens if the link count is not zero. Then we should check than the name we got from proc is the one with which we can see this file. So we call <code>stat()</code> on this name and compare <code>st_dev</code> and <code>st_inode</code> fields of it with those obtained from the fstat() call earlier. If they match the file is alive and we can just dump its name. If they don't the name we got references some other file and we fail the dump. This can be handled, but this situation is quite rare so we decided to implement support for it later.  

But what happens if the link count is not zero. Then we should check than the name we got from proc is the one with which we can see this file. So we call <code>stat()</code> on this name and compare <code>st_dev</code> and <code>st_inode</code> fields of it with those obtained from the fstat() call earlier. If they match the file is alive and we can just dump its name. If they don't the name we got references some other file and we fail the dump. This can be handled, but this situation is quite rare so we decided to implement support for it later.  

[[Category: Under the hood]]

[[Category: Under the hood]]

[[Category: Files]]

[[Category: Files]]