Volatile (ramdrive ?) folders
 

Hi, I have a network attached server (zyxel NSA310) and it seems that when I change some files after restart they disappear. Now I would like to know how can I learn which are the folders where if I change files they won't survive on restart (on linux in general). As far as I understand the lines below containing tmpfs, sysdisk.img (this one I don't understand why) are mounts where changes won't survive. I also noticed that changes to /var/spool/cron/crontabs/root are lost on restart and I don't understand why; looking below it seems to me that /var/spool/cron/crontabs shouldn't be a volatile folder.

root@nsa310:~# mount -l
rootfs on / type rootfs (rw)
/proc on /proc type proc (rw,relatime)
/sys on /sys type sysfs (rw,relatime)
none on /proc/bus/usb type usbfs (rw,relatime)
devpts on /dev/pts type devpts (rw,relatime,mode=600)
/dev/mtdblock6 on /zyxel/mnt/nand type yaffs2 (ro,relatime)
/dev/sda1 on /zyxel/mnt/sysdisk type ext2 (ro,relatime,errors=continue)
/zyxel/mnt/sysdisk/sysdisk.img on /ram_bin type ext2 (ro,relatime,errors=continue)
/zyxel/mnt/sysdisk/sysdisk.img on /usr type ext2 (ro,relatime,errors=continue)
/zyxel/mnt/sysdisk/sysdisk.img on /lib/security type ext2 (ro,relatime,errors=continue)
/zyxel/mnt/sysdisk/sysdisk.img on /lib/modules type ext2 (ro,relatime,errors=continue)
/dev/ram0 on /tmp/tmpfs type tmpfs (rw,relatime,size=5120k)
/dev/ram0 on /usr/local/etc type tmpfs (rw,relatime,size=5120k)
/dev/ram0 on /usr/local/var type tmpfs (rw,relatime,size=5120k)
/dev/mtdblock4 on /etc/zyxel type yaffs2 (rw,relatime)
/dev/md0 on /i-data/949018fd type ext4 (rw,noatime,barrier=0,data=writeback,usrquota)
/dev/sdb1 on /e-data/806e0d7ac6c3709c857f0734b8572729 type tntfs (rw,relatime,uid=99,gid=0,umask=00,nls=utf8,case_sensitive,nocache,errors=continue,mft_zone_multipli er=1) [Expansion Drive]
/dev/md0 on /usr/local/zy-pkgs type ext4 (rw,noatime,barrier=0,data=writeback,usrquota)
/dev/md0 on /etc/zyxel/zy-pkgs type ext4 (rw,noatime,barrier=0,data=writeback,usrquota)
/dev/md0 on /usr/local/apache/htdocs/zyxel/pkg type ext4 (rw,noatime,barrier=0,data=writeback,usrquota)
/dev/md0 on /usr/local/apache/web_framework/data/cache type ext4 (rw,noatime,barrier=0,data=writeback,usrquota)
/dev/mtdblock4 on /usr/local/apache/web_framework/data/config type yaffs2 (rw,relatime)


Filesystem 1K-blocks Used Available Use% Mounted on
/dev/mtdblock6 48896 37756 11140 78% /zyxel/mnt/nand
/dev/sda1 497829 490379 7450 99% /zyxel/mnt/sysdisk
/dev/loop0 123955 106426 17529 86% /ram_bin
/dev/loop0 123955 106426 17529 86% /usr
/dev/loop0 123955 106426 17529 86% /lib/security
/dev/loop0 123955 106426 17529 86% /lib/modules
/dev/ram0 5120 4 5116 1% /tmp/tmpfs
/dev/ram0 5120 4 5116 1% /usr/local/etc
/dev/ram0 5120 4 5116 1% /usr/local/var
/dev/mtdblock4 10240 1508 8732 15% /etc/zyxel
/dev/md0 480213168 325569460 154643708 68% /i-data/949018fd
/dev/sdb1 976760032 563806900 412953132 58% /e-data/806e0d7ac6c3709c857f0734b8572729
/dev/md0 480213168 325569460 154643708 68% /usr/local/zy-pkgs
/dev/md0 480213168 325569460 154643708 68% /etc/zyxel/zy-pkgs
/dev/md0 480213168 325569460 154643708 68% /usr/local/apache/htdocs/zyxel/pkg
/dev/md0 480213168 325569460 154643708 68% /usr/local/apache/web_framework/data/cache
/dev/mtdblock4 10240 1508 8732 15% /usr/local/apache/web_framework/data/config

Many embedded systems load the entire operating system into RAM so any changes must be specifically written to non volatile memory. In general with most desktop and servers all data is stored on a hard drive. I am unfamiliar with the zyxel NAS devices so I can not say exactly how it works.

Thank you; I think that the type of the file system is the only all information that could help me in addition to your remark.