Hi I have upgraded elasticsearch to 5.4 and post migration the indices appears to be like below names which makes no sense.
[root@elastic cloud-user]# cd /var/lib/elasticsearch/elasticsearch/nodes/0/indices/
[root@elastic indices]# ll
total 52
drwxr-xr-x. 8 elasticsearch elasticsearch 4096 Jun 13 06:52 **3w1OIV7tSeahyz_vyMZUeA**
drwxr-xr-x. 4 elasticsearch elasticsearch 4096 Jun 8 09:50 **44vfFl_FTgCCjKJqBxNrlQ**
drwxr-xr-x. 8 elasticsearch elasticsearch 4096 Jun 14 02:43 **Bh27njEnTh6tA58LTKPN_Q**
Marked in bold are the indices which got renamed post migration i dont know what to make of this.