FAQ

The intention of this page is to hold answers to frequently (and no so frequently) asked questions as well as some random data spread among developers' heads ;-) Note, that a big portion of FAQ-s are about why C/R fails.

• Q: Why CRIU dumps parts of read-only mappings that map the code section of a binary? For instance, there is a mapping at, say 0x400000, that maps the code of /usr/bin/something. After dump there will be at least a page at 0x400000 in the pagemap
• A: The code section may have been COWed, for instance during dynamic load of the shared libraries.

• Q: Why my test cannot do privileged operation, though I run zdtm.py as root?
• A: That's because zdtm.py runs all sub-tests from non-existing non-root user. If you need root prio in your sub-test add 'flags': 'suid' into test's .desc file.

• Q: Is it possible to do live migration from one server to another with changing the IP address?
• A: Quick answer is -- if breaking the connections is OK, then yes. In details it's described in this article.

• Q: Why does dump fail with "Cannot dump half of a stream unix connection" message in logs?
• A: There are configurations when C/R fails. This particular error is about external UNIX socket.

• Q: Why does restore fail with "... pid mismatch ..." error in logs?
• A: The PID of the process of thread CRIU tries to restore is already busy. To overcome this, try CR in namespace.

• Q: I've built CRIU, how can I make sure it works?
• A: There are two minimal things to do. First is to check the kernel and the second is run the ZDTM test suite.