Deprecation

This page collects stuff that is considered to be deprecated (and is about to be removed) and how to use older CRIU versions

Problem

Sometimes we reconsider the way CRIU works and rewrite some functionality. In order not to break backward compatibility at once, the old code is kept in CRIU for a while, but is declared as deprecated. After some time the old code is just removed and only the newer version of it stays.

So, for a deprecated functionality there are two versions of CRIU -- D and R -- that work differently with it. Before version D the old functionality exists. Between D and R both -- old and new ways of doing things work, after R only new code works, old behavior is not longer supported.

When old functionality is deprecated (and eventually removed) we try to encourage people to upgrade CRIU-s and the way they use. So, if one starts CRIU of version between D and R and the deprecated functionality is requested, the message

Deprecated functionality (...) rejected.
Use the --deprecated option or set CRIU_DEPRECATED environment.
For details visit https://criu.org/Deprecation.

appears in logs and criu exits. To continue working "the old way" w/o upgrading CRIU one may use the --deprecated option in CLI or set the CRIU_DEPRECATED environment variable.

But (!) it's important to upgrade anyway, since after some time the old functionality will still be removed and even the --deprecated/CRIU_DEPRECATED won't help.

Below is the list of stuff we deprecate with explanations.

Deprecated stuff

Per-pid rlimits, itimers and posix_timers image file

Deprecated in 2.6. Now all this stuff sit in the core entry (all since 1.3)

Separate image file for epoll tfds

Deprecated in 2.6. It's now merged into epoll image since 1.4

Removed stuff

The criu show action

Removed in 2.0. Use CRIT instead

No ids.img files

Removed in 2.1. We've been writing these files since at least v0.4, no deprecation period.

The --namespaces option

Removed in 2.2. It was used when we didn't have /proc/pid/ns stuff, now it's useless, no deprecation period.

Per-pid fdinfo.img file

Removed in 2.4. The new layout (marked with respective bit in inventory) is per-fdtable-id, no deprecation period.

Per-pid file locks

Removed in 2.4. Now all locks sit in the file-locks.img file, no deprecation period.

Old page-read

Removed in 2.4. Used at ancient times when no pagemaps existed, no deprecation period.

Plans

The criu exec action

Should be deprecated with Compel

Per-PID logs

Not sure whether anybody is using it

No file records for ttys

See collect_one_tty(). Older versions of criu (before 1.4 commit caa64d97) didn't have reg_file_entry for ttys.

All options for external resources

Need to lower the API complexity and use --external option only. Opts to deprecate: -x|--ext-unix-sk, --veth-pair, --ext-mount-map, --enable-external-*

See also

What's bad with V1 images