I try to sshfs mount a remote dir, but the mounted files are not writable. I have run out of ideas or ways to debug this. Is there anything I should check on the remote server?
I am on an Xubuntu 14.04. I mount remote dir of a 14.04 Ubuntu.
local $ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.3 LTS
Release: 14.04
Codename: trusty
I changed the /etc/fuse.conf
local $ sudo cat /etc/fuse.conf
# /etc/fuse.conf - Configuration file for Filesystem in Userspace (FUSE)
# Set the maximum number of FUSE mounts allowed to non-root users.
# The default is 1000.
#mount_max = 1000
# Allow non-root users to specify the allow_other or allow_root mount options.
user_allow_other
And my user is in the fuse group
local $ sudo grep fuse /etc/group
fuse:x:105:MY_LOACL_USERNAME
And I mount the remote dir with (tried with/without combinations of sudo, default_permissions, allow_other):
local $sudo sshfs -o allow_other,default_permissions -o IdentityFile=/path/to/ssh_key REMOTE_USERNAME@REMOTE_HOST:/remote/dir/path/ /mnt/LOCAL_DIR_NAME/
The REMOTE_USERNAME has write permissions to the dir/files (on the remote server).
I tried the above command without sudo, default_permissions, and in all cases I get:
local $ ls -al /mnt/LOCAL_DIR_NAME/a_file
-rw-rw-r-- 1 699 699 1513 Aug 12 16:08 /mnt/LOCAL_DIR_NAME/a_file
local $ test -w /mnt/LOCAL_DIR_NAME/a_file && echo "Writable" || echo "Not Writable"
Not Writable
In response to user3188445's comment:
$ whoami
LOCAL_USER
$ cd
$ mkdir test_mnt
$ sshfs -o allow_other,default_permissions -o IdentityFile=/path/to/ssh_key REMOTE_USERNAME@REMOTE_HOST:/remote/dir/path/ test_mnt/
$ ls test_mnt/
I see the contents of the dir correctly
$ ls -al test_mnt/
total 216
drwxr-xr-x 1 699 699 4096 Aug 12 16:42 .
drwxr----- 58 LOCAL_USER LOCAL_USER 4096 Aug 17 15:46 ..
-rw-r--r-- 1 699 699 2557 Jul 30 16:48 sample_file
drwxr-xr-x 1 699 699 4096 Aug 11 17:25 sample_dir
$ touch test_mnt/new_file
touch: cannot touch ‘test_mnt/new_file’: Permission denied
# extra info: SSH to the remote host and check file permissions
$ ssh REMOTE_USERNAME@REMOTE_HOST
# on remote host
$ ls -al /remote/dir/path/
lrwxrwxrwx 1 root root 18 Jul 30 13:48 /remote/dir/path/ -> /srv/path/path/path/
$ cd /remote/dir/path/
$ ls -al
total 216
drwxr-xr-x 26 REMOTE_USERNAME REMOTE_USERNAME 4096 Aug 12 13:42 .
drwxr-xr-x 4 root root 4096 Jul 30 14:37 ..
-rw-r--r-- 1 REMOTE_USERNAME REMOTE_USERNAME 2557 Jul 30 13:48 sample_file
drwxr-xr-x 2 REMOTE_USERNAME REMOTE_USERNAME 4096 Aug 11 14:25 sample_dir
The question was answered in a linux mailing list; I post a translated answer here for completeness.
The solution is not to used both the options default_permissions and allow_other (which I didn't try in my original experiments).
The problem seems to be quite simple. When you give the option default_permissions in fusermount then fuse's permission control of the fuse mount is handled by the kernel and not by fuse. This means that the REMOTE_USER's uid/gid aren't mapped to the LOCAL_USER (sshfs.c IDMAP_NONE). It works the same way as a simple nfs fs without mapping.
So, it makes sense to prohibit the access, if the uid/gid numbers don't match.
If you have the option allow_other then this dir is writable only by the local user with uid 699, if it exists.
From fuse's man:
'default_permissions'
By default FUSE doesn't check file access permissions, the
filesystem is free to implement its access policy or leave it to
the underlying file access mechanism (e.g. in case of network
filesystems). This option enables permission checking, restricting
access based on file mode. It is usually useful together with the
'allow_other' mount option.
'allow_other'
This option overrides the security measure restricting file access
to the user mounting the filesystem. This option is by default only
allowed to root, but this restriction can be removed with a
(userspace) configuration option.
Collected from the Internet
Please contact [email protected] to delete if infringement.
Comments