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This page https://help.ubuntu.com/community/mkusb encourages to create persisten live bootable USB. So that's what I suggested to my class, when I had to suggest a way how they could enjoy Ubuntu Linux without disturbing the school's computer default OS. So now they can boot Ubuntu 18.04 from their USB pen drives.

When teaching them how to set up Apache web server, it was discovered that the changes made to /etc/hosts file were not preserved between boots. The config files under /etc/apache2/sites-enabled and the site files under /var/www where preserved, though.

What could be going on here? Mkusb is using casper-rw partition in order to establish the persistence. Why would the persistence work on one file and not work on another? Or perhaps the /etc/hosts file is rewritten by some default live USB instruction that should be removed?

General discussion about persistent live systems

Some system settings are set up and some programs are started before the overlay system for persistence has started. This happens for the linux kernel and for the kernel's hardware device drivers. Maybe this is also what is happening to the /etc/hosts file. I have tampered with that file in installed systems, but not in persistent live systems, so I don't really know, if there is an easy solution to the problem.

Possible solutions

• 
  

  An obvious, but not so easy solution is to install Ubuntu (install like into an internal drive) into a USB drive. Such a system will behave like any installed system. See this link and links from it.

  
  
  

  If you don't want identical installed systems, it should be possible to set up a master installed system with the OEM method, clone it and then finish the installation in each computer making the systems unique with user names and passwords, host names etc.

  
  



• Another alternative might be to [automatically] backup /etc/hosts to a 'safe place', and at boot restore it [also automatically]. This could be done with scripts and maybe involve cron. But there should be a reason for /etc/hosts to bounce back (unless it is a bug). Maybe things involving the network and /etc/hosts happen early about in the boot process, before the overlay system is activated, and in that case, this workaround will not work.




• Yet another alternative is to try a persistent live system made from another linux distro in order to check if the /etc/hosts bounces back to default after reboot.

Test with Debian 9.6.0

mkusb can create persistent live drives from Ubuntu and Debian iso files. So it is natural for me to try a Debian persistent live system. I have the iso file

debian-live-9.6.0-amd64-cinnamon.iso

which is new (downloaded January 2019). I made and tested a persistent live system, and it preserves /etc/hosts after reboot :-)

user@debian:~$ cat /etc/hosts

127.0.0.1   localhost debian

192.168.0.4 xw8400

::1     localhost ip6-localhost ip6-loopback

ff02::1     ip6-allnodes

ff02::2     ip6-allrouters



user@debian:~$ lsb_release -a

No LSB modules are available.

Distributor ID: Debian

Description:    Debian GNU/Linux 9.6 (stretch)

Release:    9.6

Codename:   stretch



user@debian:~$ uname -a

Linux debian 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64 GNU/Linux

user@debian:~$ df -h

Filesystem      Size  Used Avail Use% Mounted on

udev            7.8G     0  7.8G   0% /dev

tmpfs           1.6G  9.4M  1.6G   1% /run

/dev/sdb4       2.0G  2.0G     0 100% /lib/live/mount/persistence/sdb4

/dev/loop0      1.9G  1.9G     0 100% /lib/live/mount/rootfs/filesystem.squashfs

tmpfs           7.8G     0  7.8G   0% /lib/live/mount/overlay

/dev/sdb5       8.4G  2.3G  5.8G  28% /lib/live/mount/persistence/sdb5

overlay         8.4G  2.3G  5.8G  28% /

tmpfs           7.8G     0  7.8G   0% /dev/shm

tmpfs           5.0M  4.0K  5.0M   1% /run/lock

tmpfs           7.8G     0  7.8G   0% /sys/fs/cgroup

tmpfs           7.8G  4.0K  7.8G   1% /tmp

tmpfs           1.6G   20K  1.6G   1% /run/user/1000

/dev/sdb1       4.2G   23M  4.2G   1% /media/user/usbdata



user@debian:~$ sudo lsblk -fm

NAME   FSTYPE   LABEL                 UUID                                 MOUNTPOINT                                 NAME     SIZE OWNER GROUP MODE

loop0  squashfs                                                            /lib/live/mount/rootfs/filesystem.squashfs loop0    1.8G root  disk  brw-rw----

sda                                                                                                                   sda    238.5G root  disk  brw-rw----

├─sda1 ext4     root                  2093f8d6-7840-4256-8edc-4db97e865784                                            ├─sda1 232.5G root  disk  brw-rw----

└─sda2 swap     swap                  4b882c9f-4867-4c5c-8eb7-c84ef03f4786                                            └─sda2     6G root  disk  brw-rw----

sdb                                                                                                                   sdb     14.9G root  disk  brw-rw----

├─sdb1 ntfs     usbdata               51B99954568550BA                     /media/user/usbdata                        ├─sdb1   4.2G root  disk  brw-rw----

├─sdb2                                                                                                                ├─sdb2     1M root  disk  brw-rw----

├─sdb3 vfat     usbboot               3FAC-E416                                                                       ├─sdb3   244M root  disk  brw-rw----

├─sdb4 iso9660  d-live 9.6.0 ci amd64 2018-11-10-11-54-14-00               /lib/live/mount/persistence/sdb4           ├─sdb4     2G root  disk  brw-rw----

└─sdb5 ext4     persistence           9d044926-15cd-4e1b-911d-ceb8e7101cf3 /lib/live/mount/persistence/sdb5           └─sdb5   8.5G root  disk  brw-rw----

sr0                                                                                                                   sr0     1024M root  cdrom brw-rw----

I don't know if things will work as they should with Debian persistent live and your Apache web server,

• if /etc/hosts and the corresponding network settings work as intended, and


• if other things in Debian, for example hardware drivers work with your computers,

but I think it is worth trying with Debian.

For a live/install iso the system boots before persistent data is mounted, so you might need to copy those /etc/hostname and /etc/hosts to the home directory, edit them and add commands in /etc/rc.local to copy them back to /etc and set hostname dynamically

It's actually interesting so many files are persistent and hosts and hostname are not

sudo -i

cp /etc/hosts /home/

cp /etc/hostname /home/

  # edit both files and save 

nano /home/hosts

nano /home/hostname

  # make sure they are root

chown root:root /home/hosts

chown root:root /home/hostname



nano /etc/rc.local

  # add those lines before line exit 0

cp /home/hostname /etc/

cp /home/hosts /etc/

hostname $(cat /etc/hostname)

  #save file

Reboot and check, should be fine.

There are similar solutions that keep files in user specific dir, but with my approach you can delete ubuntu or mint user (after creating new one and adding to sudo group) and you don't have to worry about losing hosts files