Connection reset by peer using sshfs

I was using the -F /path/to/config option. The answer was in my config file where I had

IdentityFile ~/.ssh/id_rsa

which did not work. The absolute path is required:

IdentityFile /home/user/.ssh/id_rsa

Since this error message is the default one when ssh connection fails, the most generic answer (per @peterph comment) is to investigate using at least -odebug:

sshfs -odebug,sshfs_debug,loglevel=debug ...

for example

sshfs -odebug,sshfs_debug,loglevel=debug -o Ciphers=arcfour -o Compression=no -o allow_root -o transform_symlinks localhost:/ /mnt/your_mount_point

As said elsewhere, common causes include missing allow_other in fuse.conf or missing fuse group membership (although that may not be needed anymore on Ubuntu 18.04?)

In my case this printed:

SSHFS version 2.8 FUSE library version: 2.9.7 nullpath_ok: 0 nopath: 0 utime_omit_ok: 0 executing <ssh> <-x> <-a> <-oClearAllForwardings=yes> <-ologlevel=debug> <-oIdentityFile=~/.ssh/id_rsa> <-oCiphers=arcfour> <-oCompression=no> <-2> <localhost> <-s> <sftp> command-line line 0: Bad SSH2 cipher spec 'arcfour'. read: Connection reset by peer

...pointing to an unsupported Cipher option (working on fedora but not ubuntu)

After a lot more of trying it turns out my client user wasn't in the fuse group. After I added it with sudo usermod -a -G fuse myuser the mount works fine again. Don't ask me how it could have worked before reinstalling the server. Thank for all your help!