SKALE-2844 update documentation

SEKManager.cpp

@@ -149,7 +149,7 @@ void gen_SEK() {
 
   cout << "ATTENTION! YOUR BACKUP KEY WILL BE WRITTEN INTO backup_key.txt.\n" <<
           "PLEASE COPY IT TO THE SAFE PLACE AND THEN DELETE THE FILE MANUALLY BY RUNNING THE FOLLOWING COMMAND:\n" <<
-          "`sudo apt-get install secure-delete && srm -vz backup_key.txt`" << endl;
+          "`docker exec -it <SGX_CONTAINER_NAME> bash && apt-get install secure-delete && srm -vz backup_key.txt`" << endl;
   sek_file << SEK;
 
   if (!autoconfirm) {

docs/backup-procedure.md

@@ -4,10 +4,10 @@
 
 When SGXWallet is initialized, the server will print the backup key. 
 **This key must be securely recorded and stored.**
-Be sure to store this key in a safe place, then securely remove it with the following command:
+Be sure to store this key in a safe place, then go into a docker container and securely remove it with the following command:
 
 ```bash
-sudo apt-get install secure-delete && srm -vz backup_key.txt
+docker exec -it <SGX_CONTAINER_NAME> bash && apt-get install secure-delete && srm -vz backup_key.txt
 ```
 
 Master-Slave replication is recommended to support the SGXWallet backup strategy. Below are general instructions for a basic backup and recovery process.