CentOS 7 telnet-server container issue on Proxmox 3.4

[seneca214]

Hello,

We're seeing the following issues with the telnet-server package in CentOS 7 running in a container on Proxmox 3.4. We only see this when running in a container, i.e. not with CentOS 7 install on a physical server. When logging into the server via telnet, characters are missing from the login prompt, text is not echoed back, and new lines on the screen are 'stair-stepping'. Has anyone run across this before? Any suggestions for making this work correctly? We see this happen when using a telnet client from the localhost, putty on windows and from telnet on other devices on the network.

Thanks

 

[manu]

Why do you log in with telnet and not ssh ? Passwords are sent clear text over the wire with telnet.

 

[seneca214]

telnet is required by other legacy software running on the server. SSH is used elsewhere.

 

[seneca214]

A couple notes to add to this:

* This issue does not appear with Proxmox 4.0 and CentOS 7 containers.

* On Proxmox 3.4 with CentOS 7. If you edit the /usr/lib/systemd/system/telnet@.service file changing ExecStart to be 'ExecStart=-/usr/sbin/in.telnetd -D options', telnets to the server work, however you're left with initial debugging information on the screen. Not ideal. e.g.

$ telnet localhost
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
td: send do TERMINAL TYPE
td: send do TSPEED
td: send do XDISPLOC
td: send do NEW-ENVIRON
td: recv do SUPPRESS GO AHEAD
td: send will SUPPRESS GO AHEAD
td: recv will TERMINAL TYPE
td: recv will NAWS
td: send do NAWS
td: recv will TSPEED
td: recv will LFLOW
td: send do LFLOW
td: recv will LINEMODE
td: send dont LINEMODE
td: recv will NEW-ENVIRON
td: recv do STATUS
td: send will STATUS
td: recv wont XDISPLOC
td: recv suboption NAWS 0 80 (80) 0 44 (44)
td: recv suboption TERMINAL-SPEED IS 38400,38400
td: recv suboption ENVIRON IS
td: recv suboption TERMINAL-TYPE IS "XTERM"
td: send do ECHO
td: recv wont ECHO
td: send will ECHO

Kernel 2.6.32-41-pve on an x86_64
server login: td: recv do ECHO

and the login session works and you get a normal shell. Without this you get (this is exactly how it appears on the screen with missing characters, no echo and 'stair stepping' lines:

$ telnet localhost
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

Kernel 2.6.32-41-pve on an x86_64
erver login:
Password:
ast login: Thu Nov 12 13:15:58 from test
]0;guest1@server:~[guest1@server ~]$

 

[manu]

Hi
Centos 7 on OpenVZ is not something we have tested and support.

I advise you to migrate to PVE4, which uses the future proof lxc containers.
Telnet on Centos 7 works in a LXC container:

[manu@centos7c ~]$ telnet localhost
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

Kernel 4.2.3-1-pve on an x86_64
centos7c login: manu
Password:
Last login: Mon Nov 16 15:33:46 on lxc/tty2


You can also read https://pve.proxmox.com/wiki/Convert_OpenVZ_to_LXC