After having transferred my BII "Unix" directory from one older MBA to a new MBA (Sierra 10.12.4), I discover than thousands files have been locked in the transfer ("reading only" in command-I for "wheel" and "everyone"). Could I unlock all that files easily by writing something in Terminal, instead of spending weeks in unlocking file after file in command-I ? I use the path « /HD/Users/Shared/BII/Unix/lots of locked files »

Maybe I did not get that right, you moved the Unix directory to another host?
I can´t see how you would benefit from that.

I think that vintage Mac files become locked on foreign file systems for security reasons.
If you want to move a bunch of HFS files from your emulator, best copy them to a suitable disk image.
Here are some collected: http://macintoshgarden.org/apps/disk-images-emulators
The disk image may be moved via USB thumb drive formatted ExFat or MacOS(Extended).
Best avoid FAT32 because of the 2GB file size limit.

Superuser has the Terminal things, if you wish to unlock your files that way.
https://superuser.com/questions/40749/c ... es-on-os-x

I suppose the 'Unix' directory is the BasiliskII shared folder on the OSX side. Permissions (especially the user ID) may differ between the two Macs. Best create an archive from the old shared folder, move that archive to the new MBP and decompress it there. The files will then belong to you on the new Mac. Any Mac-compatible format will do, you can compress the folder in the OSX Finder to a zip archive, or create a .dmg disk image from the folder with Disk Utility.

"Any mac compatible format" is key -- you could have a bunch of resource forks attached to those files, and you'll want to preserve those. Safest way to do this is to create a compressed image of the shared folder. This will also double as a backup that you can potentially load directly into BII.

The problem was most likely caused by attempting to access the files using a user ID different than the one that originally wrote the files (numeric user ID, not the username string, which can be the same on different computers, but will have a different numeric ID assigned for file permissions etc.)

Thank you to you all ! I looked around and found how to speak to Terminal so all my BII files are now unlocked as I wanted.