handbook/linuxemu: show how to mount linprocfs

Some programs expect procfs and other Linuxisms.

PR:		docs/195209
Reported by:	ngie

documentation/content/en/books/handbook/linuxemu/_index.adoc

@@ -111,6 +111,23 @@ On 64-bit machines, [.filename]#/etc/rc.d/abi# will automatically load the modul
 
 Since the Linux(R) binary compatibility layer has gained support for running both 32- and 64-bit Linux(R) binaries (on 64-bit x86 hosts), it is no longer possible to link the emulation functionality statically into a custom kernel.
 
+For some applications, [.filename]#/compat/linux/proc#, [.filename]#/compat/linux/sys#, and [.filename]#/compat/linux/dev/shm# may need to be mounted. Add this line to [.filename]#/etc/fstab#:
+
+....
+linprocfs  /compat/linux/proc     linprocfs   rw            0   0
+linsysfs   /compat/linux/sys      linsysfs    rw            0   0
+tmpfs      /compat/linux/dev/shm  tmpfs       rw,mode=1777  0   0
+....
+
+Then mount the filesystem accordingly:
+
+[source,bash]
+----
+# mount /compat/linux/sys
+# mount /compat/linux/proc
+# mount /compat/linux/dev/shm
+----
+
 [[linuxemu-libs-manually]]
 === Installing Additional Libraries Manually