zfs is killed with kernel update in xenial similar as with 14.04:
https://github.com/zfsonlinux/zfs/issues/5408
https://github.com/zfsonlinux/pkg-zfs/issues/219

The 14.04 issue fixed.

when i try to compile 
dkms install -m zfs -v 0.6.5.6 -k 4.4.0-59-generic

then get:
....
   CC [M]  /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.o
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c: In function '__zpl_xattr_acl_set_access':
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:1284:28: warning: passing argument 1 of 'posix_acl_valid' from incompatible pointer type [-Wincompatible-pointer-types]
     error = posix_acl_valid(acl);
                             ^
 In file included from /var/lib/dkms/zfs/0.6.5.6/build/include/linux/vfs_compat.h:204:0,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zpl.h:37,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zfs_vnops.h:34,
                  from /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:81:
 include/linux/posix_acl.h:84:12: note: expected 'struct user_namespace *' but argument is of type 'struct posix_acl *'
  extern int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
             ^
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:1284:12: error: too few arguments to function 'posix_acl_valid'
     error = posix_acl_valid(acl);
             ^
 In file included from /var/lib/dkms/zfs/0.6.5.6/build/include/linux/vfs_compat.h:204:0,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zpl.h:37,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zfs_vnops.h:34,
                  from /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:81:
 include/linux/posix_acl.h:84:12: note: declared here
  extern int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
             ^
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c: In function '__zpl_xattr_acl_set_default':
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:1323:28: warning: passing argument 1 of 'posix_acl_valid' from incompatible pointer type [-Wincompatible-pointer-types]
     error = posix_acl_valid(acl);
                             ^
 In file included from /var/lib/dkms/zfs/0.6.5.6/build/include/linux/vfs_compat.h:204:0,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zpl.h:37,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zfs_vnops.h:34,
                  from /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:81:
 include/linux/posix_acl.h:84:12: note: expected 'struct user_namespace *' but argument is of type 'struct posix_acl *'
  extern int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
             ^
 /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:1323:12: error: too few arguments to function 'posix_acl_valid'
     error = posix_acl_valid(acl);
             ^
 In file included from /var/lib/dkms/zfs/0.6.5.6/build/include/linux/vfs_compat.h:204:0,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zpl.h:37,
                  from /var/lib/dkms/zfs/0.6.5.6/build/include/sys/zfs_vnops.h:34,
                  from /var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.c:81:
 include/linux/posix_acl.h:84:12: note: declared here
  extern int posix_acl_valid(struct user_namespace *, const struct posix_acl *);
             ^
 scripts/Makefile.build:258: recipe for target '/var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.o' failed
 make[5]: *** [/var/lib/dkms/zfs/0.6.5.6/build/module/zfs/zpl_xattr.o] Error 1
 scripts/Makefile.build:403: recipe for target '/var/lib/dkms/zfs/0.6.5.6/build/module/zfs' failed
 make[4]: *** [/var/lib/dkms/zfs/0.6.5.6/build/module/zfs] Error 2
 Makefile:1420: recipe for target '_module_/var/lib/dkms/zfs/0.6.5.6/build/module' failed
 make[3]: *** [_module_/var/lib/dkms/zfs/0.6.5.6/build/module] Error 2
 make[3]: Leaving directory '/usr/src/linux-headers-4.4.0-59-generic'
 Makefile:16: recipe for target 'modules' failed
 make[2]: *** [modules] Error 2
 make[2]: Leaving directory '/var/lib/dkms/zfs/0.6.5.6/build/module'
 Makefile:685: recipe for target 'all-recursive' failed
 make[1]: *** [all-recursive] Error 1
 make[1]: Leaving directory '/var/lib/dkms/zfs/0.6.5.6/build'
 Makefile:556: recipe for target 'all' failed
 make: *** [all] Error 2
DKMSKernelVersion: 4.4.0-59-generic


please fix it.
zfs is basic.....