I have succesfully used growisofs to append content (data / files and folders) to a DVD+R.

invocation

general format

the format for composing such a command (line (invocation)) is:

growisofs -speed 2 -M /dev/dvd (mkisofs/genisoimage command line goes here).

The "-speed" switch is optional.

particular example

Here is my particular example:

# growisofs -speed 3 -M /dev/dvd -A 'mkisofs 3.01a16 growISOfs 7.1' -sysid 'name of your OS' -udf -joliet-long -long-rr-time -r errctl="WARN|ALL *" -iso-level 2 -N -publisher 'udf joliet-long -long-rr-time -r -iso-level 2 -N ucs-level 1' -p 'implicit -pad, right? no charset specified use-fileversion errctl="WARN|ALL *" ' -use-fileversion -ucs-level 1 -V 'Econee cPanel backups2013nov' -v -v -v -gui -log-file=growisofs-speed3-M_-v-v-v-gui.log.txt -graft-points sears500WD-Temp-econee_whm_cpanels=/mnt/sears/Temp/econee_whm_cpanels/
Executing 'mkisofs -C 16,525312 -M /dev/fd/3 -A mkisofs 3.01a16 growISOfs 7.1 -sysid Manjaro -udf -joliet-long -long-rr-time -r errctl=WARN|ALL * -iso-level 2 -N -publisher udf joliet-long -long-rr-time -r -iso-level 2 -N ucs-level 1 -p implicit -pad, right? no charset specified use-fileversion errctl="WARN|ALL *"  -use-fileversion -ucs-level 1 -V Econee cPanel backups2013nov -v -v -v -gui -log-file=growisofs-speed3-M_-v-v-v-gui.log.txt -graft-points sears500WD-Temp-econee_whm_cpanels=/mnt/sears/Temp/econee_whm_cpanels/ | builtin_dd of=/dev/dvd obs=32k seek=32832'
Warning: creating filesystem that does not conform to ISO-9660.
Setting input-charset to 'UTF-8' from locale.
3.01a16 (i686-pc-linux-gnu)
re-directing all messages to growisofs-speed3-M_-v-v-v-gui.log.txt
/dev/dvd: "Current Write Speed" is 4.1x1352KBps.
builtin_dd: 881520*2KB out @ average 3.8x1352KBps
/dev/dvd: flushing cache
/dev/dvd: closing track
/dev/dvd: closing session
/dev/dvd: reloading tray

result

When I query the blkid (information for the block device) of the optical disc, it still shows information about the bootable first track/session which is the (exact) same as before growisofs -M was run, when there was only one session on the disc.

blkid

# blkid /dev/sr0
/dev/sr0: LABEL="slackelLive_kde-4.10.4-64" TYPE="iso9660"

initial session was burned using

Note: the initial session (And track) on the disc was burned with:

growisofs -speed 4 -Z /dev/dvd=slackellive-kde-4.10.4-64.iso

Next, I decided to query the disc state (status) (stats) usng dvd+rw-mediainfo and then cdrdao disk-info and msinfo commands/modes/operations:

dvd+rw-mediainfo

# dvd+rw-mediainfo /dev/dvd
INQUIRY:                [Optiarc ][DVD RW AD-7260S ][1.03]
GET [CURRENT] CONFIGURATION:
 Mounted Media:         1Bh, DVD+R
 Media ID:              MBIPG101/R05
 Current Write Speed:   4.0x1385=5540KB/s
 Write Speed #0:        16.0x1385=22160KB/s
 Write Speed #1:        12.0x1385=16620KB/s
 Write Speed #2:        8.0x1385=11080KB/s
 Write Speed #3:        6.0x1385=8310KB/s
 Write Speed #4:        4.0x1385=5540KB/s
GET [CURRENT] PERFORMANCE:
 Write Performance:     4.0x1385=5540KB/s@[0 -> 2295103]
 Speed Descriptor#0:    03/2295104 R@16.0x1385=22160KB/s W@16.0x1385=22160KB/s
 Speed Descriptor#1:    03/2295104 R@12.0x1385=16620KB/s W@12.0x1385=16620KB/s
 Speed Descriptor#2:    00/2295104 R@8.0x1385=11080KB/s W@8.0x1385=11080KB/s
 Speed Descriptor#3:    00/2295104 R@8.0x1385=11080KB/s W@6.0x1385=8310KB/s
 Speed Descriptor#4:    00/2295104 R@5.0x1385=6925KB/s W@4.0x1385=5540KB/s
READ DVD STRUCTURE[#0h]:
 Media Book Type:       00h, DVD-ROM book [revision 0]
 Legacy lead-out at:    2295104*2KB=4700372992
READ DISC INFORMATION:
 Disc status:           appendable
 Number of Sessions:    3
 State of Last Session: empty
 "Next" Track:          3
 Number of Tracks:      3
READ TRACK INFORMATION[#1]:
 Track State:           partial/complete
 Track Start Address:   0*2KB
 Free Blocks:           0*2KB
 Track Size:            523264*2KB
READ TRACK INFORMATION[#2]:
 Track State:           partial/complete
 Track Start Address:   525312*2KB
 Free Blocks:           0*2KB
 Track Size:            881520*2KB
READ TRACK INFORMATION[#3]:
 Track State:           blank
 Track Start Address:   1408880*2KB
 Next Writable Address: 1408880*2KB
 Free Blocks:           886224*2KB
 Track Size:            886224*2KB
 ROM Compatibility LBA: 0
FABRICATED TOC:
 Track#1  :             17@0
 Track#2  :             17@525312
 Track#AA :             17@1406832
 Multi-session Info:    #2@525312
READ CAPACITY:          1406832*2048=2881191936

cdrdao

disk-info

# cdrdao disk-info /dev/sr0
Cdrdao version 1.2.3 - (C) Andreas Mueller <andreas@daneb.de>
/dev/sr0: Optiarc DVD RW AD-7260S       Rev: 1.03
Using driver: Generic SCSI-3/MMC - Version 2.0 (options 0x0000)

That data below may not reflect the real status of the inserted medium
if a simulation run was performed before. Reload the medium in this case.

CD-RW                : no
Total Capacity       : 35:03:64 (157789 blocks, 308/353 MB)
CD-R medium          : n/a
Recording Speed      : n/a
CD-R empty           : no
Toc Type             : CD-DA or CD-ROM
Sessions             : 2
Last Track           : 2
Appendable           : yes
Start of last session: 525312 (116:46:12)
Start of new session : 1409030 (313:09:05)

msinfo

# cdrdao msinfo /dev/sr0
Cdrdao version 1.2.3 - (C) Andreas Mueller <andreas@daneb.de>
/dev/sr0: Optiarc DVD RW AD-7260S       Rev: 1.03
Using driver: Generic SCSI-3/MMC - Version 2.0 (options 0x0000)

525312,1409030
msinfo: Session is appendable

User:Fleetwood/Growisofs usage