Mounting Remote Directories With SSHFS On Debian Squeeze - Page 2

4 Using SSHFS As A Regular User

server1:

I want to use the local user falko now and mount the remote directory /home/someuser/backup, owned by someuser, to the local directory /home/falko/backup.

Create the user falko, if it doesn't exist:

adduser falko

server2:

On server2, create the user someuser, if it does not exist:

adduser someuser

Then become someuser...

su someuser

... and go to someuser's home directory where you create the backup (/home/someuser/backup) directory - make sure it's owned by someuser (it should be anyway as you are running these commands as someuser):

cd
mkdir ~/backup
chown someuser ~/backup

You can leave the someuser account if you like:

exit

server1:

First add falko to the fuse group:

adduser falko fuse

Now go to the falko account:

su falko

Create the local /home/falko/backup directory and make sure it's owned by falko (it should be anyway as you are running these commands as falko):

cd
mkdir ~/backup
chown falko ~/backup

Then mount the remote /home/someuser/backup directory to /home/falko/backup (still as user falko) - you can either use a relative or the full path for the remote directory:

sshfs -o idmap=user [email protected]:backup ~/backup

or

sshfs -o idmap=user [email protected]:/home/someuser/backup ~/backup

-o idmap=user makes that it does not matter if the local and the remote system use different user IDs - files owned by the remote user are also owned by the local user. If you don't use this, you might get permission problems.

If you connect to the remote host for the first time, you will see a warning about the authenticity of the remote host (if you have connected to the remote host before using ssh or scp, you will not see the warning). In any case, you will be asked for the someuser password for server2:

falko@server1:~$ sshfs -o idmap=user [email protected]:/home/someuser/backup ~/backup
The authenticity of host '192.168.0.101 (192.168.0.101)' can't be established.
RSA key fingerprint is 25:d8:7a:ee:c2:4b:1d:92:a7:3d:16:26:95:56:62:4e.
Are you sure you want to continue connecting (yes/no)?
<-- yes
[email protected]'s password: <-- server2_someuser_password
falko@server1:~$

Let's check if the remote directory got mounted to /home/falko/backup:

mount

falko@server1:~$ mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
[email protected]:/home/backup on /backup type fuse.sshfs (rw,nosuid,nodev,max_read=65536)
[email protected]:/home/someuser/backup on /home/falko/backup type fuse.sshfs (rw,nosuid,nodev,max_read=65536,user=falko)
falko@server1:~$

df -h

falko@server1:~$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              29G  1.2G   26G   5% /
tmpfs                 249M     0  249M   0% /lib/init/rw
udev                  244M  100K  244M   1% /dev
tmpfs                 249M     0  249M   0% /dev/shm
[email protected]:/home/someuser/backup
                       29G  1.2G   27G   5% /home/falko/backup
falko@server1:~$

Looks good!

To unmount the share, run

fusermount -u ~/backup

or

fusermount -u /home/falko/backup

 

4.1 Creating A Private/Public Key Pair On server1

Of course, we don't want to type in a password every time we try to mount the remote share. Therefore we create a private/public key pair and transfer the public key to server2 so that we will not be asked for a password anymore.

server1:

Create a private/public key pair on server1.example.com (still as user falko):

ssh-keygen

falko@server1:~$ ssh-keygen
Generating public/private rsa key pair.
Enter file in which to save the key (/home/falko/.ssh/id_rsa):
 <-- ENTER
Enter passphrase (empty for no passphrase): <-- ENTER
Enter same passphrase again: <-- ENTER
Your identification has been saved in /home/falko/.ssh/id_rsa.
Your public key has been saved in /home/falko/.ssh/id_rsa.pub.
The key fingerprint is:
14:14:0b:ba:04:a7:51:1b:67:59:94:d5:01:7e:55:21 [email protected]
The key's randomart image is:
+--[ RSA 2048]----+
|  o.+ +=*+oo.E.oo|
|   = *...+  ...  |
|  . +   o . .    |
|   . . .   .     |
|    .   S        |
|                 |
|                 |
|                 |
|                 |
+-----------------+
falko@server1:~$

It is important that you do not enter a passphrase otherwise mounting will not work without human interaction so simply hit ENTER!

Next, we copy our public key to server2.example.com:

ssh-copy-id -i $HOME/.ssh/id_rsa.pub [email protected]

Now check on server2 if server1's public key has correctly been transferred:

server2:

cat /home/someuser/.ssh/authorized_keys

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQC+YpgpAaFYDYV2N0j4xteTx44tsz1pnSSQZPa0GkBi/KTuAJVT8DV4Jzh/HvJnNXvoyT6cEcnJa6p1SQTpn3Xt7b5ItA2ckDYTm78q1HZwX3htrkDUPrKGRwfzovyf/HKop0kHawU+Fox1nmtM9xIEVBCPERBKL0TZjGuqfEo0m6lkatVChI8RIu9+wH9I8VZCHalz+QdjQ8Mp/ckdGfVdAry4SyFicjg4eVzTq7s54yXupcSio7v2Ql95XO6azWzrU+G7VsI3UM0GMH9aXxjikx3dusmvLN9jBkL096Sheik1C7DOGVVsP6upCRVTcY6AB4J8VEmumdI4tnsSsr+x [email protected]

Now back on server1, try to mount the remote share again as user falko (make sure it's unmounted before you run the command):

server1:

sshfs -o idmap=user [email protected]:/home/someuser/backup ~/backup

If all goes well, you should not be prompted for a password:

falko@server1:~$ sshfs -o idmap=user [email protected]:/home/someuser/backup ~/backup
falko@server1:~$

 

4.2 Mounting The Remote Share Automatically At Boot Time

server1:

If you don't want to mount the remote share manually, it is possible to have it mounted automatically when the system boots (provided you have followed chapter 4.1 because otherwise an automatic mount is not possible because you will be asked for a password). Normally we would modify /etc/fstab to achieve this, but unfortunately the network isn't up yet when /etc/fstab is processed in the boot process, which means that the remote share cannot be mounted.

To circumvent this, we simply add our mount command to /etc/rc.local, which is the last file to be processed in the boot process, and at that time the network is up and running.

You need root privileges to edit /etc/rc.local, so become root first:

su

vi /etc/rc.local

#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

/usr/bin/sshfs -o idmap=user [email protected]:/home/backup /backup
cd /home/falko && su -c "/usr/bin/sshfs -o idmap=user [email protected]:/home/someuser/backup /home/falko/backup" falko
exit 0

As you see, I've added the command

cd /home/falko && su -c "/usr/bin/sshfs -o idmap=user [email protected]:/home/someuser/backup /home/falko/backup" falko

instead of just

/usr/bin/sshfs -o idmap=user [email protected]:/home/someuser/backup /home/falko/backup

because the sshfs command must be run by falko, not root!

You can test now by simply rebooting your system:

reboot

After the reboot, you can check with

mount

and

df -h

if the remote share got mounted.

 

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