Root access by SSH denied

[Nulkoud]

Hello all,

Yesterday I upgraded from the beta 4 to the current 4 release. I noticed that I'm not allowed anymore to login via SSH with the root account. I can login with the admin account, but to get the opt ware working again, I need to have root access. Is there somebody who have the same issue?
Any idea howto fix this?

thanks

[Kriskmk]

did you have the usual port 22 for ssh or something else? are you sure ssh is turned on in terminal? What error message if any are you getting?

[Nulkoud]

Hi,

getting access with the admin account it working great, so ssh isn't the problem. I use Putty to login, when I try to login with the root account the window will close immediately.

When I'm logged in as admin and try to get root access with su, I get the following error:
su: must be suid to work properly

I googled the error and found that it should be a permissions issue with /bin/su. The problem is that I can't chmod /bin/su because admin seems not allowed to do that.

Any ideas?

Thanks

[bud77]

Check your /etc/passwd and look for the root user line, and verify root has a proper shell

[Nulkoud]

Ah, thanks!

root has a shell in the path /opt, but /opt wasn't existing anymore after the update.

thanks a lot!

[bud77]

You're welcome

If I remember correctly, it should be a /bin/ash for root

[Nulkoud]

That's correct, it was /opt/bin/bash beacuse of some modifications I did. I just forgot that the /opt dir is always missing after a firmware update.

[maxxfi]

EDIT: what I described below is NOT SAFE on a Synology NAS.

Instead of mangling with /etc/passwd file, add as last line of root's .profile something like:
exec /opt/bin/bash
That will launch bash (closing default ash) when you login in, but only if it finds it.
So after an update (or more generally if /opt gets broken) you can still login as root.

Instead, this is a safer way to do it:

Code: Select all

if [ -x /opt/bin/bash ]; then
  exec /opt/bin/bash
fi

[Nulkoud]

I understand what you mean, but I don't know how this works.
Am I right that the 'profile' file is a kind of script which will be called after login?
Is it true that when I edit the profile like you sad, there will be a bash opened into another bash or do you mean that it will close the default (b)ash?

[maxxfi]

Yes, .profile is a "configuration" file that is automatically run by any sh/ash/bash, typically to set a few variables and user customization.
When you have something like "exec <command>" the current shell (in this case, ash) launches <command> and terminate itself, freeing memory and resources.

[judge146]

Hi maxxfi,

I added the line exec /opt/bin/bash to the .profile file of the root-user. However, now I am unable to login as root anymore. The error message "-ash: exec: line 22: /opt/bin/bash: not found" is displayed in the terminal window and the session is ended. Can you please help me out?

[maxxfi]

I added the line exec /opt/bin/bash to the .profile file of the root-user. However, now I am unable to login as root anymore. The error message "-ash: exec: line 22: /opt/bin/bash: not found" is displayed in the terminal window and the session is ended. Can you please help me out?

Hmm... it seems that you don't have /opt/bin/bash available.
I was surprised that the 'exec' instruction did not stop when it detected that the command was not existing. I tested with my DS and it is unfortunately true: normally on a sane Linux distro exec would avoid to exit the current shell if the command request fails:

bash: /opt/bin/notexistingshell: No such file or directory
Connection closed by foreign host.

but Synology is using busybox, and it seems busybox doesn't implement this safety net.

I'm very sorry for the issue. I'll try to come up with some trick in order to recover the situation.
BTW, could you please tell me which model of DS do you have?

[scientastic]

I have a similar issue. I upgraded/migrated from a DiskStation 212+ to a 712+, but forgot that the architecture is dissimilar. Now /opt/bin/bash won't run because it's the wrong architecture. So... my quandary is that I can't log in to edit /etc/passwd, and I need to edit /etc/passwd to enable login.

Any idea how to get around this? Any idea how to access the root filesystem without telnet or SSH access?

Thanks!

[memento]

So... my quandary is that I can't log in to edit /etc/passwd, and I need to edit /etc/passwd to enable login.

I'm in the same boat right now. Any tips on how to resolve this? Can I boot the box from a thumbdrive?

[Jeankrill]

I did the same, messed up the /root/.profile and then could not log in as root anymore over SSH and the web DSM did not work at all.

So I logged in as 'admin' and that worked fine, but I did not have the rights to change /root/.profile, so I required root access by running the 'su' command:

Diskstation>su root

it asked for a password and my old root password did not work anymore, but I tried with the default synology root password 'synopass' and it worked.

Then I went on and corrected my mistakes in /root/.profile and now everything works like a charm.

I'm a linux noob, but I hope this works for you guys too.