add default values in fstab_lines

It's useful for passing a full fstab line including like fs_passno so fsck
can take effect.

Previously it's assumed that there's no fs_freq and fs_passno in fstab lines
so original code just append "0 0" at the end of each fstab lines.

Improve this issue by assign default value in case they are not passed in.
Three field are handled here:
fs_mntops: default to "defaults"
fs_freq: default to "0"
fs_passno: default to "2"

Signed-off-by: Dave Young <dyoung@redhat.com>

dracut.8.asc

@@ -311,9 +311,13 @@ provide a valid _/etc/fstab_.
 **--add-fstab** _<filename>_::
     Add entries of _<filename>_ to the initramfs /etc/fstab.
 
-**--mount** "_<device>_ _<mountpoint>_ _<filesystem type>_ _<filesystem options>_"::
-    Mount _<device>_ on _<mountpoint>_ with _<filesystem type>_ and _<filesystem
-    options>_ in the initramfs
+**--mount** "_<device>_ _<mountpoint>_ _<filesystem type>_ [_<filesystem options>_ [_<dump frequency>_ [_<fsck order>_]]]"::
+    Mount _<device>_ on _<mountpoint>_ with _<filesystem type>_ in the
+    initramfs. _<filesystem options>_, _<dump options>_ and _<fsck order>_ can
+    be specified, see fstab manpage for the details.
+    The default _<filesystem options>_ is "defaults".
+    The default _<dump frequency>_ is "0".
+    the default _<fsck order>_ is "2".
 
 **--add-device** _<device>_ ::
     Bring up _<device>_ in initramfs, _<device>_ should be the device name.

dracut.sh

@@ -1234,7 +1234,11 @@ if [[ $kernel_only != yes ]]; then
     [[ $kernel_cmdline ]] && printf "%s\n" "$kernel_cmdline" >> "${initdir}/etc/cmdline.d/01-default.conf"
 
     while pop fstab_lines line; do
-        printf "%s\n" "$line 0 0" >> "${initdir}/etc/fstab"
+        line=($line)
+        [ -z "${line[3]}" ] && line[3]="defaults"
+        [ -z "${line[4]}" ] && line[4]="0"
+        [ -z "${line[5]}" ] && line[5]="2"
+        echo "${line[@]}" >> "${initdir}/etc/fstab"
     done
 
     for f in $add_fstab; do