Questions[directory-structure](ubuntu)

I am trying to optimize my new fs layout, and I wondered, where is it safe to use noatime? I understand that e.g. mutt uses the access/creation/modify time, and whatever else may be using that, in whichever dir.

Following a ton of guides, I have partitioned my dirs according to different use-cases, but I don't really know, where is it safe to put noatime?

dirs / flags:

/               defaults
   (/bin
    /sbin
    /lib*
    /etc
    /root
    /dev ...)

/boot           defaults
/boot/EFI       defaults

/usr            defaults,ro,nodev
                    NOTE: dpkg needs rw
/usr/share      defaults,ro,nodev,nosuid

/var            defaults,nodev
                    NOTE: /var/lib/dpkg/info -> exec
/var/tmp        defaults,nodev,nosuid,noexec
/var/log        defaults,nodev,nosuid,noexec

/opt            defaults,nodev

/tmp            defaults,nodev,nosuid,noexec
                    NOTE: some installer may need exec

/home           defaults,nodev,nosuid

I install .zip / .tar.gz programs in ~/.local/bin, but Ubuntu have /usr/local directory with content same as in ~/.local.

So, what is difference between this directories except for sudo access?

I've just reinstalled Ubuntu 16.04 on my machine, and I'm in the process of installing everything I had installed previously. This includes a few programs that I put in /usr/local/bin, but that directory doesn't seem to exist:

$ ls -A /usr/local
etc  games  include  lib  man  sbin  share  src

I don't remember explicitly creating /usr/local/bin on my old install, and yet it existed there. Why doesn't it exist by default, and how did it come to exist on my previous installation?

I have the following directory structure:

$ directory tree Data
Data
├── Mercury
├── Venus
├── Earth
│   ├── Australia
│   └── Asia
│     └── Japan
|       └── Hokkido   
├── Mars
    ├── HellasBasin
    └── SyrtisCrater

How can rename/number/label all the directories recursively to get a result similar to the following?

Data
    ├── 01
    ├── 02
    ├── 03
    │   ├── 031
    │   └── 032
    │     └── 0321
    |       └── 03211   
    ├── 04
        ├── 041
        └── 042

The idea is to rename the whole tree with new names (numbers, letters or combination of them). They don't necessary have to have labels like 03211.

Thanks in advance for your time.

Still a greenee at Linux as there are so many different approaches/ways to do the same thing. When I attempt to update to Ubuntu 17 I receive:

"The upgrade has aborted. The upgrade needs a total of 317 M free space on disk '/var'. Please free at least an additional 55.4 M of disk space on '/var'. Empty your trash and remove temporary packages of former installations using 'sudo apt-get clean'."

How can I safely reduce the size of this directory?

Filesystem             Size  Used Avail Use% Mounted on
udev                   2.0G     0  2.0G   0% /dev
tmpfs                  396M  6.0M  390M   2% /run
/dev/sda1              9.1G  2.8G  5.9G  32% /
tmpfs                  2.0G     0  2.0G   0% /dev/shm
tmpfs                  5.0M     0  5.0M   0% /run/lock
tmpfs                  2.0G     0  2.0G   0% /sys/fs/cgroup
/dev/sda5              9.1G  824M  7.8G  10% /home
/dev/sda7              922M  612M  248M  72% /var
/dev/sda11             922M  1.2M  858M   1% /run/shm
/dev/sda8              922M   21M  839M   3% /var/log
/dev/sda10             226M  2.1M  208M   1% /var/tmp
/dev/sda6              923M  8.5M  851M   1% /tmp
/dev/sda9              922M  8.7M  850M   2% /var/log/audit
//10.2.222.31/DOCMgmt  500G  216G  285G  44% /mnt/win1/DocMgmt
//10.2.222.31/LOGS     250G   89G  162G  36% /media/logs
tmpfs                  396M     0  396M   0% /run/user/1000