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A Symbolic link is similar to a Shortcut in Windows-speak or an Alias in MacOS. It's a pointer to a file
/usr/src$ ln -s linux-2.4/ linux
is the command to make a symbolic link called "linux" which points to the file linux-2.4/
Are you sure you have the command written properly as it implies that it's linking to some unknown file in the directory linux-2.4/?
The "/" looks wrong.
what do the ‘’ and ‘linux’ preset ?
I'm not sure what you mean here, do you mean preset or represent?
'target kernel' would be linux-2.4 or whatever version of the kernel you had installed.