read-only file system


i’m trying to backup some files from a remote windows 8 machine running synctrazor, to a NAS running Ubuntu 16 with an encrypted BTRFS filesystem. Every syncthing is up to date. Procedure is as following:

sudo cryptsetup luksOpen /dev/sda sda

sudo mount /dev/mapper/sda /NASS


from this point on i’m able to send and receive files over the network with several windows machines. than i want to start syncing


than i add the folder on my workstation, and make it share with the NAS. workstation is scanning… NAS messages "workstation wants to share a folder…" i add the name and path on the BTRFS filesystem


but i always get these messages from my NAS’s syncthing

mkdir /NASS: read-only file system

mkdir /NASS/remotebackup/.stfolder: no such file or directory

mkdir works fine when running from the commandline under the logged in user, and persmissions look good:

ls -l /

shows the logged in user has permissions drwxrwxrwx on /NASS. Does anybody have a hint what could be wrong? greetings.

Permissions have no meaning if the filesystem as a whole is read only, which seems to be the case in your case. Command line file creationg might work at / but not at /NASS etc.

as said, the filesystem is perfectly read/writeable via samba, also

touch /NASS/remotebackup/test.log

works fine

echo foobar > /NASS/remotebackup/test.log

writes to this file and mount shows

/dev/mapper/sda on /NASS type btrfs (rw,relatime,space_cache,subvolid=5,subvol=/)

so syncthing is misinterpreting something, under both accounts, local user and superuser.

Can you show a full startup log?


this is what i get on the commandline while startup

chorn@NASS:~$ syncthing
[monitor] 13:59:22 INFO: Starting syncthing
[VISGX] 13:59:22 INFO: syncthing v0.14.39 "Dysprosium Dragonfly" (go1.9 linux-amd64) 2017-09-25 06:05:21 UTC [noupgrade]
[VISGX] 13:59:23 INFO: Single thread SHA256 performance is 153 MB/s using minio/sha256-simd (129 MB/s using crypto/sha256).
[VISGX] 13:59:24 INFO: Hashing performance with weak hash is 111.77 MB/s
[VISGX] 13:59:24 INFO: Hashing performance without weak hash is 147.87 MB/s
[VISGX] 13:59:24 INFO: Weak hash disabled, as it has an unacceptable performance impact.
[VISGX] 14:02:31 WARNING: Creating directory for "Gamestation Backup complete" (jwujs-khypf): mkdir /NASS: read-only file system
[VISGX] 14:02:31 WARNING: Creating folder marker: mkdir /NASS/remotebackup/.stfolder: no such file or directory
[VISGX] 14:02:31 INFO: Ready to synchronize "Gamestation Backup complete" (jwujs-khypf) (readwrite)
[VISGX] 14:02:31 WARNING: Stopping folder "Gamestation Backup complete" (jwujs-khypf) - folder path missing
[VISGX] 14:02:31 INFO: Stopping folder "Gamestation Backup complete" (jwujs-khypf) due to error: folder path missing
[VISGX] 14:02:31 INFO: Failed initial scan of readwrite folder "Gamestation Backup complete" (jwujs-khypf)
[VISGX] 14:02:31 INFO: Send rate is unlimited, receive rate is unlimited
[VISGX] 14:02:31 INFO: Rate limits do not apply to LAN connections
[VISGX] 14:02:31 INFO: Using discovery server ht tps://
[VISGX] 14:02:31 INFO: TCP listener ([::]:22000) starting
[VISGX] 14:02:31 INFO: Using discovery server ht tps://
[VISGX] 14:02:32 INFO: Skipping pull of "Gamestation Backup complete" (jwujs-khypf) due to folder error: folder path missing
[VISGX] 14:02:33 INFO: GUI and API listening on
[VISGX] 14:02:33 INFO: Access the GUI via the following URL: ht tp://
[VISGX] 14:02:33 INFO: Device GARDV5V-DXNYQEK-ZN4GAYM-A3DJKUW-27RLGQ7-A252YA2-2YQVTUO-HXJQVA6 is "Workstation" at [dynamic]
[VISGX] 14:02:42 INFO: Skipping pull of "Gamestation Backup complete" (jwujs-khypf) due to folder error: folder path missing
[VISGX] 14:02:42 INFO: Detected 1 NAT device
[VISGX] 14:02:44 INFO: Joined relay relay://
[VISGX] 14:02:52 INFO: Skipping pull of "Gamestation Backup complete" (jwujs-khypf) due to folder error: folder path missing
[VISGX] 14:04:17 INFO: Established secure connection to GARDV5V-DXNYQEK-ZN4GAYM-A3DJKUW-27RLGQ7-A252YA2-2YQVTUO-HXJQVA6 at (tcp-server) (TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305)
[VISGX] 14:04:17 INFO: Device GARDV5V-DXNYQEK-ZN4GAYM-A3DJKUW-27RLGQ7-A252YA2-2YQVTUO-HXJQVA6 client is "syncthing v0.14.39" named "Gamestation"


Seems it does a mkdirall, which does it step by step and fails at the root which is potentially read only.

Which is reasonable, but shouldn’t happen if the folder path exists. We only end up in the MkdirAll if we get a “does not exist” back for the stat of the folder path…

Perhaps fs abstraction anomaly?

is there anything i can do to help with this? any stats to provide? any configuration on my machine? i really do not know how to get further.


Well you can pre-create the directories yourself, if that helps, create an issue on github.

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.