Have you consider looking at man su
to see the command line parameters? Or even a
$ su --help
Usage: su [OPTION]... [-] [USER [ARG]...]
Change the effective user id and group id to that of USER.
-, -l, --login make the shell a login shell
-c, --command=COMMAND pass a single COMMAND to the shell with -c
--session-command=COMMAND pass a single COMMAND to the shell with -c
and do not create a new session
-f, --fast pass -f to the shell (for csh or tcsh)
-m, --preserve-environment do not reset environment variables
-p same as -m
-s, --shell=SHELL run SHELL if /etc/shells allows it
--help display this help and exit
--version output version information and exit
A mere - implies -l. If USER not given, assume root.
Report bugs to <firstname.lastname@example.org>.
Of course the brief --help
output above assumes that you understand that a "login shell" means that the shell is started as though it was a de novo
Bottom line: Try su -
instead of a simple su