OK Graham - sync did wait on Fedora for the data to finish flushing to disk - its an older Fedora and the sync command is version "sync (coreutils) 8.15". Both ClearOS 6 and 7 have newer versions so would expect them to execute in the same manner...
Monitored data transfer activity both by watching my gkrellm displays as well as field 9 in the output of "watch -n 2 cat /sys/block/sdc/sdc1/stat" run in a terminal. Field 9 counted down to '0', the gkrellm indicated transfer had finished and the sync command returned all at virtually the same time.
Incidentally - if using a device with partitions then the stat file to monitor would be in this format "/sys/block/sdc/sdc1/stat" - in this example partition 1 on device sdc...
So it should be safe to umount and unplug the USB device after the sync command returns - assuming no more write have been subsequently issued to the USB drive.
Are you aware of a way of forcing the USB drive to flush and report safe to remove?
Good Question... paranoid answers
The safest way is to..
Issue the "sync" command ***
Monitor the "/sys/block/<device>/stat" file for a 0. It counts down as the buffered data is flushed.
(Note that if the USB drive has more than one partition - you have multiple <devices> to monitor
When the file(s) report 0, umount the device(s)
A number of other options are often used...
1. If the the USB device has a blinking light to indicate activity - wait until it stops blinking, then umount.
2. Monitor disk activity in real time. Since Fedora is used here - have gkrellmd running on all systems and monitored on a Fedora virtual desktop using gkrellm. Therefore can monitor disk activity for any partition on any drive on any system visually. Umount after activity stops.
3. Determine some arbitrary time that is longer than what should be necessary for the flush to complete and wait for that time period... umount
4. Issue the umount command and monitor the devices mounted and wait until the USB drive disappears before removing it.
*** There is conflicting information on the web regarding the sync command .Some say it returns immediately - others that is only returns once the sync is complete. Will test to see what Fedora does and update here...
How is Linux if you eject the disk without doing it through the O/S will it screw the drive up like Windows will if there are any pending writes or does Linux always write directly to the disk without caching so that once it's completed a backup you can remove it?
Don't use USB drives with ClearOS - but do with Fedora. It caches. When copying large media files notice that the copy can take up to several minutes to complete after the system indicates it is ready for more commands. Removing the USB drive before the cache is empty obviously creates incomplete file(s) and corruption. Suspect ClearOS could be the same...
Know nothing about BMBackup as custom rsync scripts are used here. Maybe all the drives could have the same label and mounted using the "LABEL=xxxxx" option? Not sure of the wisdom of this... you would need to think that through.
What you want cannot be done with just the ClearOS software suite, you are gong to have to roll your sleeves up and get to work...
Here's some ideas to get you started. Doubt any of these will run without modification under ClearOS so get busy creating your own unique version...
On Community Edition for both 6.x and 7.x have used 'groupinstall' for 'Development Tools'... Just " --enablerepo=centos-unverified"
i.e. yum groupinstall "Developemtn Tools"--enablerepo=centos-unverified
Most convenient way to install them...
7.3 here (not upgraded yet to 7.4)
and here this is 6.9
In the unlikely event anybody is still using any of the kmod drivers from my site (haven't advertised them in a long time now) - please follow the directions in Nick's append - https://www.clearos.com/clearfoundation/social/community/clearos-7-4-community-edition-released#reply-192411
Sometimes a problem like this can resolved by changing a setting in the program you use to view the mail...
For example with Thunderbird
Edit -> Account Settings -> "Name of Account" -> Server Settings
There is a Section "When I delete a message" with options as follows
Move it to this folder (Default Folder is Trash)
Just mark it deleted
Remove it immediately
Note the current setting
Select "Remove it immediately" and save "OK"
See if you can now delete the email
Go back and restore your previous "When I delete a message" option
Seamonkey mail is almost the same - suspect others possibly have similar options
Thanks Nick - so Webconfig detects the problem if you go back to configure dhcp settings.. so ClearOS does some basic checking, that is good. Your suggestion to add more, even better... In the meantime, if you change your network, re-check the dhcpd settings screen...
Anything in the logs recorded at the time you changed the NIC address and subnet to indicate an invalid dhcp config now existed? If nothing, would indicate no monitoring by default within dnsmasq for an invalid situation arising during operation . ISC dhcpd detected the NIC/subnet change as a problem within the same minute it changed... Checked the dnsmasq man pages online, (as they are not on my system ) and only found a reference to a syntax check. That is good, but a configuration file that has correct syntax can still be completely invalid...
Regardless of what got changed - surely there should error displayed as soon as something becomes inconsistent...
While dhcpd was running, changed one of the sub-nets where dynamic addresses are assigned but no current leases in effect. Almost instantly dhcpd provided this error message and continued running, recognising the sub-net had disappeared... Had changed 192.168.8.0/24 to 192.168.9.0/24 - my 'play' VLAN
Oct 18 21:26:16 karien dhcpd: receive_packet failed on enp2s0.8: Network is down
Re-starting dhcpd now gives this helpful advice
Oct 18 21:39:18 karien dhcpd: No subnet declaration for enp2s0.8 (192.168.9.98).
Oct 18 21:39:18 karien dhcpd: ** Ignoring requests on enp2s0.8. If this is not what
Oct 18 21:39:18 karien dhcpd: you want, please write a subnet declaration
Oct 18 21:39:18 karien dhcpd: in your dhcpd.conf file for the network segment
Oct 18 21:39:18 karien dhcpd: to which interface enp2s0.8 is attached. **
If dnsmasq does no checking - then maybe webconfig could do some basic checks when the dnsmasq dhcp entries are displayed, created or updated? That would help avoid the situation the OP is faced with... No idea what the webconfig screen(s) look like...
A bit OT... The real reason didn't use dnsmasq in the first place? Couldn't find how to operate two dnsmasq dhcpd servers on the same sub-nets co-operating with each other. Same with dns. The ISC dhcpd server does this with a master and slave that communicate. Both therefore 'know' which leases it has assigned, as well as those by its 'partner'. If one goes down, the other will do everything. Then, when the failed system comes back up, it is brought 'up to date' by its partner... Similarly with BIND for dns. You can have a master and as many slaves as you want. Any changes made to the master get synced to the slave(s). The slave(s) will continue operating if the master goes down. Thus can take down a ClearOS server wjhile the rest of the systems still function fully with dns and dhcp available.
yuk... as Nick pointed out the below is totally wrong (amongst other problems) - trying to assign dhcp addresses outside the subnet
Have to assume you did a copy-and-paste and this is not a typo
Doesn't dnsmasq run any verification checks before it runs? - if not, that is really bad - should not even start with something configured like that... Is there no dnsmasq utility either to verify the configuration files used by dnsmasq..
Don't use dnsmasq here (and seeing this really glad not using it), but the following
Use several VLANS here and tried to configure an incorrect range for dhcpd on a VLAN
It would not start and spit out this helpful error message
-- Unit dhcpd.service has begun starting up.
Oct 18 11:37:25 karien.sraellis.com dhcpd: Internet Systems Consortium DHCP Server 4.2.5
Oct 18 11:37:25 karien.sraellis.com dhcpd: Copyright 2004-2013 Internet Systems Consortium.
Oct 18 11:37:25 karien.sraellis.com dhcpd: All rights reserved.
Oct 18 11:37:25 karien.sraellis.com dhcpd: For info, please visit https://www.isc.org/software/dhcp/
Oct 18 11:37:25 karien.sraellis.com dhcpd: bad range, address 192.168.9.64 not in subnet 192.168.8.0 netmask 255.255.255.0