[One (M7) Original Android Development] nkk71:
some remarks above in bold blue

I honestly can't reproduce, nor see what could be wrong

I have NuSenSeveN v4 ROM + the built-in NuK3rn3l kernel (however I have SELinux permissive)

when installing a secondary ROM (TWRP->Advanced->MultiROM->Add ROM), it changes the "mount points",

for example this is me flashing ViperOne 7.0.2 to secondary

the information from /tmp/recovery.log, I have highlighted the important info in bold blue:

I:operation_start: 'Installing'
Installing ROM ViperOne_7.0.2...
[B][COLOR="Blue"]Creating folders and images for type 1[/COLOR][/B]
I:Running cmd "chcon u:object_r:system_file:s0 "/data/media/0/multirom/roms//ViperOne_7.0.2/system";chcon u:object_r:system_data_file:s0 "/data/media/0/multirom/roms//ViperOne_7.0.2/data";chcon u:object_r:cache_file:s0 "/data/media/0/multirom/roms//ViperOne_7.0.2/cache";"

Flashing ZIP file /sdcard/0NKK/ViperOne_7.0.2.zip
ROM: ViperOne_7.0.2
Preparing ZIP file...
rm: can't remove '/tmp/mr_update.zip': No such file or directory
I:Running cmd "mkdir -p /tmp/META-INF/com/google/android/"
I:ZIP size limit for /tmp: 768.91 MB
I:Modifying ZIP /sdcard/0NKK/ViperOne_7.0.2.zip in place, gonna restore it later
I:Running cmd "cd /tmp && zip "/sdcard/0NKK/ViperOne_7.0.2.zip" META-INF/com/google/android/updater-script"
updating: META-INF/com/google/android/updater-script (deflated 88%)

[B][COLOR="Blue"]Changing mounts to ROM ViperOne_7.0.2...[/COLOR][/B]

I:Mount: Unable to find partition for path '/data'
I:Backup folder set to '/realdata/media/0/TWRP/BACKUPS/HT34PW914024'
mtppipe remove storage 65537
I:mount -o bind '/realdata/media/0' '/sdcard' process ended with RC=0
I:Processing '/data_t'
I:Created '/data_t' folder.
I:Processing '/system'
I:Processing '/cache'
I:Recreating /cache/recovery folder.

Partition Logs:
/boot | /dev/block/mmcblk0p33 | Size: 16MB Raw size: 0

Flags: Can_Be_Backed_Up IsPresent Can_Flash_Img
Primary_Block_Device: /dev/block/mmcblk0p33
Display_Name: Boot
Storage_Name: boot
Backup_Path: /boot
Backup_Name: boot
Backup_Display_Name: Boot
Storage_Path: /boot
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/devlog | /dev/block/mmcblk0p22 | Size: 19MB Used: 16MB Free: 3MB Backup Size: 16MB Raw size: 20971520

Flags: Can_Be_Mounted Can_Be_Wiped IsPresent
Primary_Block_Device: /dev/block/mmcblk0p22
Display_Name: devlog
Storage_Name: devlog
Backup_Path: /devlog
Backup_Name: devlog
Backup_Display_Name: devlog
Storage_Path: /devlog
Current_File_System: ext4
Fstab_File_System: ext4
Backup_Method: files

/misc | /dev/block/mmcblk0p19 | Size: 0MB Raw size: 0

Flags: IsPresent
Primary_Block_Device: /dev/block/mmcblk0p19
Display_Name: misc
Storage_Name: misc
Backup_Path: /misc
Backup_Name: misc
Backup_Display_Name: misc
Storage_Path: /misc
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/recovery | /dev/block/mmcblk0p34 | Size: 15MB Raw size: 0

Flags: IsPresent Can_Flash_Img
Primary_Block_Device: /dev/block/mmcblk0p34
Display_Name: Recovery
Storage_Name: recovery
Backup_Path: /recovery
Backup_Name: recovery
Backup_Display_Name: Recovery
Storage_Path: /recovery
Current_File_System: emmc
Fstab_File_System: emmc
Backup_Method: dd

/realdata | /dev/block/mmcblk0p37 | Size: 26206MB Used: 168MB Free: 20509MB Backup Size: 168MB Raw size: 27917287424

Flags: Can_Be_Mounted Can_Be_Wiped Wipe_During_Factory_Reset Wipe_Available_in_GUI IsPresent Can_Be_Encrypted Has_Data_Media Can_Encrypt_Backup Use_Userdata_Encryption Is_Storage Is_Settings_Storage
Symlink_Path: /realdata/media/0
Symlink_Mount_Point: /sdcard
Primary_Block_Device: /dev/block/mmcblk0p37
Display_Name: Realdata
Storage_Name: Internal Storage
Backup_Path: /data
Backup_Name: data
Backup_Display_Name: Data
Storage_Path: /realdata/media/0
Current_File_System: ext4
Fstab_File_System: ext4
Backup_Method: files
MTP_Storage_ID: 65537

/usb-otg | | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB Raw size: 0

Flags: Can_Be_Mounted Can_Be_Wiped Wipe_Available_in_GUI Removable Is_Storage
Primary_Block_Device: /dev/block/sda1
Alternate_Block_Device: /dev/block/sda
Display_Name: USB-OTG
Storage_Name: USB-OTG
Backup_Path: /usb-otg
Backup_Name: usb-otg
Backup_Display_Name: USB-OTG
Storage_Path: /usb-otg
Current_File_System: auto
Fstab_File_System: auto
Backup_Method: files
MTP_Storage_ID: 65538

[B][COLOR="Blue"]/data | /realdata/media/0/multirom/roms/ViperOne_7.0.2/data | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB Raw size: 0[/COLOR][/B]

Flags: Can_Be_Mounted Can_Be_Wiped Use_Rm_Rf Can_Be_Backed_Up IsPresent Ignore_Blkid
Primary_Block_Device: /realdata/media/0/multirom/roms/ViperOne_7.0.2/data
Display_Name: Data
Storage_Name: data_t
Backup_Path: /data
Backup_Name: data
Backup_Display_Name: Data
Storage_Path: /data_t
Current_File_System: ext4
Fstab_File_System: ext4
Bind_Of: /realdata
Backup_Method: files

[B][COLOR="Blue"]/system | /realdata/media/0/multirom/roms/ViperOne_7.0.2/system | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB Raw size: 0[/COLOR][/B]

Flags: Can_Be_Mounted Can_Be_Wiped Use_Rm_Rf Can_Be_Backed_Up Wipe_Available_in_GUI IsPresent Ignore_Blkid
Primary_Block_Device: /realdata/media/0/multirom/roms/ViperOne_7.0.2/system
Display_Name: System
Storage_Name: System
Backup_Path: /system
Backup_Name: system
Backup_Display_Name: System
Storage_Path: /system
Current_File_System: ext4
Fstab_File_System: ext4
Bind_Of: /realdata
Backup_Method: files

[B][COLOR="Blue"]/cache | /realdata/media/0/multirom/roms/ViperOne_7.0.2/cache | Size: 0MB Used: 0MB Free: 0MB Backup Size: 0MB Raw size: 0[/COLOR][/B]

Flags: Can_Be_Mounted Can_Be_Wiped Use_Rm_Rf Can_Be_Backed_Up Wipe_During_Factory_Reset Wipe_Available_in_GUI IsPresent Ignore_Blkid
Primary_Block_Device: /realdata/media/0/multirom/roms/ViperOne_7.0.2/cache
Display_Name: Cache
Storage_Name: Cache
Backup_Path: /cache
Backup_Name: cache
Backup_Display_Name: Cache
Storage_Path: /cache
Current_File_System: ext4
Fstab_File_System: ext4
Bind_Of: /realdata
Backup_Method: files

I:Running cmd "dd if="/dev/block/mmcblk0p33" of="/realdata/media/0/multirom/roms/ViperOne_7.0.2/boot.img""
32768+0 records in
32768+0 records out
16777216 bytes (16.0MB) copied, 1.228241 seconds, 13.0MB/s
Current boot sector was used as base for fake boot.img!
I:Running cmd "echo '/dev/block/mmcblk0p33' > /tmp/mrom_fakebootpart"
I:Running cmd "mv "/dev/block/mmcblk0p33" "/dev/block/mmcblk0p33-orig""
I:Running cmd "ln -s "/realdata/media/0/multirom/roms/ViperOne_7.0.2/boot.img" "/dev/block/mmcblk0p33""
Installing '/realdata/media/0/0NKK/ViperOne_7.0.2.zip'...
Checking for MD5 file...
Skipping MD5 check: no MD5 file found
I:Zip does not contain SELinux file_contexts file in its root.
I:Legacy property environment initialized.
aroma/s: Initializing
Starting AROMA INSTALLER version 2.70B6
(c) 2013 by amarullz xda-developers

Starting AROMA INSTALLER version 2.70B6
(c) 2013 by amarullz xda-developers
...
AROMA INSTALLER Finished...
...
ZIP successfully installed
...
Restoring mounts...
...
Updating partition details...
I:mount -o bind '/data/media/0' '/sdcard' process ended with RC=0
I:Data backup size is 168MB, free: 18929MB.
I:sending message to remove 65537
I:Message sent, remove storage ID: 65537
mtppipe remove storage 65537
I:Unable to mount '/usb-otg'
I:Actual block device: '', current file system: 'auto'
...done
I:Unable to find storage partition '/realdata/media/0'.
I:mount -o bind '/data/media/0' '/sdcard' process ended with RC=0
I:Backup folder set to '/data/media/0/TWRP/BACKUPS/HT34PW914024'
Extracting contents of boot.img...
I:Running cmd "rm -r "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/"*"
rm: can't remove '/data/media/0/multirom/roms//ViperOne_7.0.2/boot/*': No such file or directory
rm: can't remove '/tmp/boot': No such file or directory
Ramdisk uses GZIP compression
2821 blocks
I:Running cmd "cp -a /tmp/boot/*.rc "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/default.prop "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/init "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/main_init "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
cp: can't stat '/tmp/boot/main_init': No such file or directory
I:Running cmd "cp -a /tmp/boot/fstab.* "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/file_contexts "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/property_contexts "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/seapp_contexts "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "cp -a /tmp/boot/sepolicy "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/""
I:Running cmd "mv "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/init" "/data/media/0/multirom/roms//ViperOne_7.0.2/boot/main_init""
I:Running cmd "cd "/data/media/0/multirom/roms//ViperOne_7.0.2/boot" && rm cmdline ramdisk.gz zImage"
rm: can't remove 'cmdline': No such file or directory
rm: can't remove 'ramdisk.gz': No such file or directory
rm: can't remove 'zImage': No such file or directory
Injecting boot.img..
I:Running cmd ""/data/media/0/multirom/trampoline" --inject="/data/media/0/multirom/roms//ViperOne_7.0.2/boot.img" --mrom_dir="/data/media/0/multirom" -f"
I:Set page: 'action_complete'
I:operation_end - status=0

as you can see, /data is re-routed to --> /realdata/media/0/multirom/roms/ViperOne_7.0.2/data

so even if the updater-script wipes /data, it is actually wiping the "fake" /realdata/media/0/multirom/roms/ViperOne_7.0.2/data

my setup:

Recovery

: TWRP_multirom-20150704-v32f-UNOFFICIAL-m7univ.img

MultiROM

: multirom-20150623-v32f-UNOFFICIAL-m7univ.zip

Primary ROM

: NuSenseSeven v4 + built-in NuK3rn3l (SELinux permissive)

Secondary ROMs

: anything, at the moment

CM12

ViperOne 7.0.2

AICP

Sense7_ArtMod