Further details for offline environments (#955) (#960)

Fixes #955

doc/how_to_guides/offline.md

@@ -17,8 +17,10 @@ The way of transfer depends on the environment. The files to be transferred are
 ## Import the vulnerability database file on the offline system
 The vulnerability database should be copied into ~/.cache/cve-bin-tool
 
-## Run cve-bin-tool with --update never option
-In an offline environment, when running a scan specify `--update never` so that cve-bin-tool doesn't attempt to download the latest database files.
+## Run cve-bin-tool with --update never  and --disable-version-check options
+In an offline environment, when running a scan specify `--update never` so that cve-bin-tool doesn't attempt to download the latest database files and `--disable-version-check` so that the cve-bin-tool doesn't attempt to check for a newer version of the tool.
 
 ## Maintenance Updates
 In an offline environment, it is important to update the vulnerability database on a regular basis as often as you feel appropriate, so that the scanner can continue to detect recently-identified vulnerabilities. If any changes to CVE data is required (e.g. to remove false positives), you might also want to create and copy over a triage data file for usage.
+
+It is important to periodically check if the cve-bin-tool has also been updated as this check cannot be performed within an offline environment.