Как переключиться между 12 и 24-часовым временем в Ubuntu Touch?

ответ:

chmod a+rw filename

проверить эту таблицу:

#   Permission      rwx
7   full                111
6   read and write      110
5   read and execute    101
4   read only       100
3   write and execute   011
2   write only      010
1   execute only        001
0   none                000

, а затем

chmod a+r file  read is added for all
chmod a-x file  execute permission is removed for all
chmod a+rw file change the permissions of the file file to read and write for all.
chmod +rwx file On some UNIX platforms such as BSD, this will restore the permission of the file file to default: -rwxr-xr-x.
chmod u=rw,go= file read and write is set for the owner, all permissions are cleared for the group and others
chmod -R u+w,go-w docs  change the permissions of the directory docs and all its contents to add write access for the user, and deny write access for everybody else.
chmod = file    removes all privileges for all.