How to fix request failed on channel 0
pty, ssh, terminal
Solution
PTY allocation request failed on channel 0
There is a limit of 256 pseudo terminals on a system. Maybe you have an application that is leaking pseudo terminals. Use
lsof /dev/pts/*
to see what processes have open pseudo-terminals
shell request failed on channel 0
I was getting this error (without PTY allocation error). It turns out that one of my applications (QtCreator 3.0.?) was leaking Zombie processes. Other users were able to log in so I might have been hitting my per user process quota (if there is such a thing). I've updated to QtCreator 3.3. So far so good.
Problem
When I want to connect to my server like this ``` ssh -a username@my-server.de -p 22 ``` it gives me two error messages: ``` PTY allocation request failed on channel 0 shell request failed on channel 0 ``` When I use the parameter `-T` the first error message goes away. But how to fix the second one? I can't connect. To other servers I can connect without any problems. I'm on MAC OS 10.9. The parameter `-v` shows me this debug output: ``` OpenSSH_6.2p2, OSSLShim 0.9.8r 8 Dec 2011 debug1: Reading configuration data /etc/ssh_config debug1: /etc/ssh_config line 20: Applying options for * debug1: Connecting to xxx.your-server.de [188.40.3.15] port 22. debug1: Connection established. debug1: identity file /Users/xxx/.ssh/id_rsa type -1 debug1: identity file /Users/xxx/.ssh/id_rsa-cert type -1 debug1: identity file /Users/xxx/.ssh/id_dsa type -1 debug1: identity file /Users/xxx/.ssh/id_dsa-cert type -1 debug1: Enabling compatibility mode for protocol 2.0 debug1: Local version string SSH-2.0-OpenSSH_6.2 debug1: Remote protocol version 2.0, remote software version mod_sftp/0.9.8 debug1: no match: mod_sftp/0.9.8 debug1: SSH2_MSG_KEXINIT sent debug1: SSH2_MSG_KEXINIT received debug1: kex: server->client aes128-ctr hmac-md5 none debug1: kex: client->server aes128-ctr hmac-md5 none debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP debug1: SSH2_MSG_KEX_DH_GEX_INIT sent debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY debug1: Server host key: RSA 55:f5:ca:ca:01:45:0f:7b:71:0a:1f:ba:9e:25:17:fb debug1: Host 'xxx.your-server.de' is known and matches the RSA host key. debug1: Found key in /Users/xxx/.ssh/known_hosts:1 debug1: ssh_rsa_verify: signature correct debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug1: SSH2_MSG_NEWKEYS received debug1: Roaming not allowed by server debug1: SSH2_MSG_SERVICE_REQUEST sent debug1: SSH2_MSG_SERVICE_ACCEPT received debug1: Authentications that can continue: publickey,password debug1: Next authentication method: publickey debug1: Trying private key: /Users/xxx/.ssh/id_rsa debug1: Trying private key: /Users/xxx/.ssh/id_dsa debug1: Next authentication method: password ``` After I enter the password, I get this: ``` debug1: Authentication succeeded (password). Authenticated to xxx.your-server.de ([xxx.xxx.3.15]:22). debug1: channel 0: new [client-session] debug1: Entering interactive session. debug1: Sending environment. debug1: Sending env LANG = de_DE.UTF-8 shell request failed on channel 0 ```