Unable to write to new partitions

[Ralf Mardorf]

On Sat, 17 Mar 2018 18:18:00 +0100, Ralf Mardorf wrote:
>On Sat, 17 Mar 2018 18:09:49 +0100, Volker Wysk wrote:
>>Am Samstag, 17. März 2018, 23:39:47 CET schrieb Bret Busby:  
>>> On 17/03/2018, Volker Wysk <post at volker-wysk.de> wrote:    
>>> > Am Samstag, 17. März 2018, 21:34:16 CET schrieb Bret Busby:    
>>> >> Hello.
>>> >>
>>> >> I shrank the boot partitions of teo installed operating systems,
>>> >> and, for each thence created unallocated space, I created a new
>>> >> sext4 partition, to which, I assigned the respective labels
>>> >> Data05 and Data06.
>>> >>
>>> >> I then, from within my UbuntuMATE 16.04 installation, ran sudo
>>> >> chmod 777 on each new partition, so as to enable read+write
>>> >> access to the two partitions.
>>> >>
>>> >> But, I can not write to the two partitions.    
>>> >
>>> > Might they be mounted read-only? What is in your /etc/fstab?
>>> >    
>>> 
>>> None of the Dataxx partitions are displayed in running
>>> cat /etc/fstab as me (user) - the Dataxx partitions are mounted by
>>> selecting them using the Places -> Removable media facility.
>>> 
>>> Data01 to Data04 are readable and writable, being mounted this
>>> way.    
>>
>>Try "mount | egrep Data". This tells you the mount options of the
>>mounted partitions, on the right side of the line. This should start
>>with "(rw,..." or "(ro,...".
>>
>>  
>>> > Have you done a reboot after you changed your partitions? (Just
>>> > guessing)   
>>> 
>>> I do not remember whether I had rebooted after running the chmod
>>> commands on the two partitions, but, as the system crashed/froze
>>> while I was trying to reload firefox before rebooting (to try to
>>> avoid losing the last session, as mozilla abolished the Save session
>>> functionality), I have now rebooted, after running the chmod 660
>>> command as advised on both partitions, and they are sill not
>>> writable.    
>>
>>I meant, after you changed your partition table(s).  
>
>Regarding the actuall culprit/pitfall this is completely irrelevant. No
>x bit on a folder, no write access, since indexing fails.

PS:

"The execute permission grants the ability to execute a file. This
permission must be set for executable programs, in order to allow the
operating system to run them. When set for a directory, the execute
permission is interpreted as the search permission: it grants the
ability to access file contents and meta-information if its name is
known, but not list files inside the directory, unless read is set also.

The effect of setting the permissions on a directory, rather than a
file, is "one of the most frequently misunderstood file permission
issues".[8]" -
https://en.wikipedia.org/wiki/File_system_permissions#Permissions

The [8] is for

"Execute (x)
    The ability to cd into this directory, and access the files in this
directory." - https://www.hackinglinuxexposed.com/articles/20030424.html