Stub some syscalls to run programs which expect syscalls that don't exist in iSH. The syscalls return -1 indicating failure, so the program will hopefully recognise that the syscall is bogus. The stubbed syscalls are mostly esoteric enough that they shouldn't break the program's execution.
Compile the hack with
gcc -O2 -shared -o /usr/local/lib/<name>.so <name>.c
Use it with
LD_PRELOAD=/usr/local/lib/<name>.so <program>
You'll probably want to alias the program to do that automatically, for example by
adding the following to a shell startup script like .profile:
alias qemu='LD_PRELOAD=/usr/local/lib/qemu-hack.so qemu-system-i386'
Unless the program relies heavily on the stubbed syscalls, its speed shouldn't be affected much. Any slowness is probably due to iSH's nature as an emulator.
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qemu-system-i386works, but it's so slow it can't be used for much more than testing 16-bit real mode programs. Emulating a whole Linux machine would probably be unbearably slow. -
ffmpegalso works, but is also horribly slow (I got 0.01x conversion speed on a relatively new iPhone).
Because iSH doesn't include these stubbed syscalls yet. If you're tired of using this hack, contribute to iSH and stub (or implement, if you're feeling ambitious) the syscalls there.