How to make mkinitcpio busybox ash to source /etc/profile?

Question

Arch Linux /usr/lib/initcpio/busybox is owned by package mkinitcpio-busybox 1.27.2-1 and is configured low on features, for example CONFIG_FEATURE_USE_INITTAB is not set.

In a custom initramfs, containing that busybox, I managed to get ssh network logins that do source /etc/profile working. Also there is an ash shell prompt visible on the VGA monitor.

However that "vga" shell doesn't source /etc/profile. Q:Difference between Login Shell and Non-Login Shell? makes me think that this shell is not a login shell. That shell is started by /init:

exec setsid sh -c 'exec sh </dev/tty1 >/dev/tty1 2>&1'

Regression:

• exec setsid sh -c 'exec sh -i </dev/tty1 >/dev/tty1 2>&1'
• exec setsid sh -c 'exec sh - </dev/tty1 >/dev/tty1 2>&1'
• exec setsid sh -c 'exec -sh </dev/tty1 >/dev/tty1 2>&1'

How to make this busybox ash shell to source /etc/profile and/or make it an (auto) login shell?

Answer 1

Conventionally, a shell acts as a login shell if it is invoked with a command name beginning with -. exec -sh would work is you had an executable called -sh in the path. BusyBox ash also supports the -l option, so you can run sh -l.

When you log in, the login program (or sshd, or whatever is handling the login) takes care of running the user's shell with a leading - in the command name (the command name doesn't have to be the same as the name of the executable, it's just a very common convention which login violates on purpose). Here, “whatever is handling the login” is your mini-script, so you have to take care of it.