How to add a symbolic link to bypass unavailable busybox applet
Thinking error. You've created a link named busybox pgrep, linking to a (not existing) other file of the same name. What you probably wanted to achieve is:

ln -sf &lt;/path/to/alternative/&gt;busybox &lt;/path/to/linkdir/&gt;pgrep


Replace &lt;/path/to/alternative/&gt; with the path to the busybox binary featuring pgrep functionality, and &lt;/path/to/linkdir/&gt; with the path to a directory contained in your $PATH (best the one where the other symlinks reside).

Busyboxes usually decide their "wanted functionality" by checking where they're called from. So the symlink is simply named pgrep, grep, or whatever, and pointing to the busybox binary.