Followup-For: Bug #742282 Hi Giorgos,
Does your script trigger this behaviour with btrfs-tools-3.17-1.1? If it doesn't, great! If it does, please read on. #1: There are known issues with btrfs send|receive when operating on volumes mounted with the default subvolume (subvolid=5); This is what happens with a simple mkfs.btrfs /dev/sdX && mount /dev/sdX /mnt/1. The following instructions exists primarily to gather the negative results necessary to confirm this. If it works, you will have succeeded in providing data that disproves commonly held btrfs lore. #2 and #3 are also possible causes. #2: If you still get "no such file or directory," it may be that that you've encountered one of the "timing issues" in btrfs. There are fewer and fewer of these with every release, but I still keep a couple of "work around the timing issues" lines in my backup scripts. For the record, my scripts don't use btrfs send|receive, and I had timing issues which hung subvolume management until the system was rebooted. I've also read about some nasty interactions between the loop subsystem and btrfs...it might be worth increasing the sleep times even more, in case transactions are stalling somewhere in the loop. It would be appreciated if you could find a small usb flash drive to test this, to eliminate the loop subsystem as a contributing factor. #3: I've read that another data needs to be committed to the disk before a snapshot actually exists. This would also explain why you received a "no such file or directory" error. Arguably, this is part of the #2 group of issues, but I've broken it out into it's own point because #2 is a huge and complicated category of issues. #3 can be eliminated simply by making sure that the data is physically on the disk (eg: sync the FS to get it into a consistent state, then sync to disk). Could you please try replacing the btrfs sub section and the btrfs send section with the following: btrfs sub create mnt/1/subv sleep 3 date > mnt/1/subv/fileA btrfs fi sync /mnt/1 sleep 3 sync sleep 3 btrfs sub snap -r mnt/1/subv mnt/1/subvROsnap1 date > mnt/1/subv/fileB btrfs fi sync /mnt/1 sleep 3 sync sleep 3 btrfs sub snap -r mnt/1/subv mnt/1/subvROsnap2 btrfs send mnt/1/subvROsnap1 | btrfs receive mnt/2 btrfs fi sync /mnt/1 sleep 3 sync sleep 3 btrfs send -p mnt/1/subvROsnap1 mnt/1/subvROsnap2 | btrfs receive mnt/2 ###### and also, if you have the time, please test this one too: btrfs sub create mnt/1/subv sleep 3 date > mnt/1/subv/fileA btrfs sub sync /mnt/1/subv sleep 3 sync sleep 3 btrfs sub snap -r mnt/1/subv mnt/1/subvROsnap1 date > mnt/1/subv/fileB btrfs sub sync /mnt/1 sleep 3 sync sleep 3 btrfs sub snap -r mnt/1/subv mnt/1/subvROsnap2 btrfs send mnt/1/subvROsnap1 | btrfs receive mnt/2 btrfs sub sync /mnt/1 sleep 3 sync sleep 3 btrfs send -p mnt/1/subvROsnap1 mnt/1/subvROsnap2 | btrfs receive mnt/2 Kind regards, Nicholas
