rear recover process is killed by OOM killer.

Issue

• rear recover process is killed by OOM killer.

RESCUE rhel7:~ # rear -v recover
Relax-and-Recover 2.4 / Git
Using log file: /var/log/rear/rear-rhel7.log
Running workflow recover within the ReaR rescue/recovery system
Starting required daemons for NFS: RPC portmapper (portmap or rpcbind) and rpc.statd if available.
Started RPC portmapper 'rpcbind'.
RPC portmapper 'rpcbind' available.
RPC status rpc.statd available.
Started rpc.idmapd.
Killed   <==

• The server has 8GB RAM which should be enough for rear recover. However, right after booting from rescue image, there is almost no available memory.

RESCUE rhel7:~ # free -m:
              total        used        free      shared  buff/cache   available
Mem:           7966        7405         104          11         456          29
Swap:             0           0           0

• No process is consuming so much memory.