LP #1526467: xtrabackup crashes with docker

**Reported in Launchpad by Rémy Phelipot last update 11-07-2016 10:00:45

MariaDB is running in a docker container and a volume is mounted on the host for the database files. I'm trying to backup the database with xtrabackup but I've got this error:

xtrabackup --backup --target-dir=test --host=10.10.10.96 --user=root
151215 17:24:39 version_check Connecting to MySQL server with DSN 'dbi:mysql:;mysql_read_default_group=xtrabackup;host=10.10.10.96;port=3306;mysql_socket=/var/run/mysqld/mysqld.sock' as 'root' (using password: YES).
151215 17:24:39 version_check Connected to MySQL server
151215 17:24:39 version_check Executing a version check against the server...
151215 17:24:39 version_check Done.
151215 17:24:39 Connecting to MySQL server host: 10.10.10.96, user: root, password: set, port: 3306, socket: /var/run/mysqld/mysqld.sock
Using server version 10.0.21-MariaDB-1~jessie
2015-12-15 17:24:39 7fec27b46780 InnoDB: Assertion failure in thread 140652255143808 in file backup_copy.cc line 648
InnoDB: Failing assertion: realpath(first, real_first) != NULL
InnoDB: We intentionally generate a memory trap.
InnoDB: Submit a detailed bug report to http://bugs.mysql.com.
InnoDB: If you get repeated assertion failures or crashes, even
InnoDB: immediately after the mysqld startup, there may be
InnoDB: corruption in the InnoDB tablespace. Please refer to
InnoDB: http://dev.mysql.com/doc/refman/5.6/en/forcing-innodb-recovery.html
InnoDB: about forcing recovery.
17:24:39 UTC - xtrabackup got signal 6 ;
This could be because you hit a bug or data is corrupted.
This error can also be caused by malfunctioning hardware.
We will try our best to scrape up some info that will hopefully help
diagnose the problem, but since we have already crashed,
something is definitely wrong and this may fail.

Thread pointer: 0x0
Attempting backtrace. You can use the following information to find out
where mysqld died. If you see no messages after this, something went
terribly wrong...
stack_bottom = 0 thread_stack 0x10000
xtrabackup(my_print_stacktrace+0x2e) [0x94eebe]
xtrabackup(handle_fatal_signal+0x262) [0x90fcf2]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x10340) [0x7fec27722340]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0x39) [0x7fec25e86cc9]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7fec25e8a0d8]
xtrabackup() [0x5a9f03]
xtrabackup(get_mysql_vars(st_mysql*)+0x42d) [0x5a639d]
xtrabackup(xb_init()+0x12b) [0x59b67b]
xtrabackup(main+0x641) [0x57e101]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf5) [0x7fec25e71ec5]
xtrabackup() [0x5922c6]

Please report a bug at https://bugs.launchpad.net/percona-xtrabackup

I've tried to execute this command inside the container and it work successfully, but it seems impossible to save the database from the host or another container. I've also tried unsuccessfully to set the --datadir option to the host directory .

Can someone reproduce this issue? Do you have a solution?