I did more experiments. If I try generating a new mylocale.tcz without any mylocale.tcz currently loaded, the process succeeds (a 667k mylocale.tcz extension is created):
$ tce-status -i | grep locale
[note no hits]
$ tce-load -wi getlocale
getlocale.tcz.dep OK
Downloading: getlocale.tcz
Connecting to gnuser.ddns.net (192.168.10.1:80)
saving to 'getlocale.tcz'
getlocale.tcz 100% |********************************| 4096 0:00:00 ETA
'getlocale.tcz' saved
getlocale.tcz: OK
[The below shows up in a different terminal after I've selected the locale I want]
Now processing... /
Locales installed. Creating extension... \
Done. The extension is at /mnt/sda3/tce/optional/mylocale.tcz and in onboot.lst
Reboot with lang=xyz (for example lang=en_US.UTF-8) to start using this.
Press enter to quit.
If I try generating a new mylocale.tcz with mylocale.tcz already loaded, the process fails (a 4k mylocale.tcz extension is created):
$ tce-status -i | grep locale
mylocale
$ tce-load -wi getlocale
getlocale.tcz.dep OK
Downloading: getlocale.tcz
Connecting to gnuser.ddns.net (192.168.10.1:80)
saving to 'getlocale.tcz'
getlocale.tcz 100% |********************************| 4096 0:00:00 ETA
'getlocale.tcz' saved
getlocale.tcz: OK
[The below shows up in a different terminal after I've selected the locale I want]
Now processing... cannot open locale archive "/usr/lib/locale/locale-archive": Read-only file system
Locales installed. Creating extension... \
Done. The extension is at /mnt/sda3/tce/optional/mylocale.tcz and in onboot.lst
Reboot with lang=xyz (for example lang=en_US.UTF-8) to start using this.
Press enter to quit.
It seems the script should error-out if it "cannot open locale archive"--as it is, the script seems to succeed in the end (causing user to interpret "cannot open locale archive" as a benign warning).