Added documentation references for file system table configuration

Author: nickanderson

cf-agent/nfs.c

@@ -481,6 +481,9 @@ int VerifyInFstab(EvalContext *ctx, char *name, const Attributes *a, const Promi
     }
 
 #if defined(__QNX__) || defined(__QNXNTO__)
+    // QNX documents 4 fstab fields : https://www.qnx.com/developers/docs/7.1/index.html#com.qnx.doc.neutrino.utilities/topic/f/fstab.html
+    // specialdevice mountpoint type mountoptions
+    // TODO Remove DUMP and PASS options used here (unsupported)?
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "%s \t %s %s\t%s 0 0", device, mountpt, fstype, opts);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #elif defined(_CRAY)
@@ -492,9 +495,13 @@ int VerifyInFstab(EvalContext *ctx, char *name, const Attributes *a, const Promi
     assert(ret >= 0 && ret < CF_BUFSIZE);
     break;
 #elif defined(__hpux)
+    // HP-UX documents 7 fstab fields: https://nixdoc.net/man-pages/HP-UX/man4/fstab.4.html
+    // deviceSpecialFile directory type options backupFrequency passNumber comment
+    // TODO Bring promise comment in as the 7th comment field # promise comment (stripped of newlines)
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "%s %s \t %s \t %s 0 0", device, mountpt, fstype, opts);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #elif defined(_AIX)
+    // AIX uses /etc/filesystems: https://www.ibm.com/docs/en/aix/7.2.0?topic=files-filesystems-file
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE,
                                      "%s:\n\tdev\t= %s\n\ttype\t= %s\n\tvfs\t= %s\n\tnodename\t= %s\n\tmount\t= true\n\toptions\t= %s\n\taccount\t= false\n",
                                      mountpt, rmountpt, fstype, fstype, host, opts);
@@ -503,12 +510,18 @@ int VerifyInFstab(EvalContext *ctx, char *name, const Attributes *a, const Promi
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "%s \t %s \t %s \t %s", device, mountpt, fstype, opts);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #elif defined(__NetBSD__) || defined(__OpenBSD__) || defined(__DragonFly__) || defined(__FreeBSD__) || defined(__APPLE__)
+    // BSDs document 6 fstab fields https://man.freebsd.org/cgi/man.cgi?fstab(5)
+    // Device Mountpoint FStype Options Dump Pass
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "%s \t %s \t %s \t %s 0 0", device, mountpt, fstype, opts);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #elif defined(__sun) || defined(sco) || defined(__SCO_DS)
+    // SunOS uses /etc/fstab and documents 7 fields: https://docs.oracle.com/cd/E19455-01/805-6331/fsadm-59727/index.html
+    // deviceToMount deviceToFsck mountPoint FStype fsckPass automount? mountOptions
+    // - is used for deviceToFsck for read-only and network based file systems
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "%s - %s %s - yes %s", device, mountpt, fstype, opts);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #elif defined(__CYGWIN__)
+    // https://cygwin.com/cygwin-ug-net/using.html#mount-table
     NDEBUG_UNUSED int ret = snprintf(fstab, CF_BUFSIZE, "/bin/mount %s %s", device, mountpt);
     assert(ret >= 0 && ret < CF_BUFSIZE);
 #else