added capabilities info

Capabilities-and-smaps.md

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+On some Linux versions it may be impossible for non-root users to read smaps files.
+
+The file may appear to allow read:
+
+```text
+$ ls -l /proc/$$/smaps
+-r--r--r-- 1 oracle oinstall 0 Apr  1 14:26 /proc/28953/smaps
+```
+
+Even so, the Linux capabilities system may prevent you from reading the file.
+
+This can be changed by setting the `CAP_SYS_PTRACE' capability for `cat`:
+
+```text
+# getcap /usr/bin/cat
+# setcap cap_sys_ptrace+ep /usr/bin/cat
+# getcap /usr/bin/cat
+/usr/bin/cat = cap_sys_ptrace+ep
+
+```
+
+While it may not be a good idea to do this to `cat`, it is fine on this test system.
+
+And now oracle can read its own smaps file:
+
+```text
+$ wc /proc/$$/smaps
+756 2522 23287 /proc/28953/smaps
+```
+
+More information is available via `man capabilities`
+
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