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 server 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
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.
unmount and mount /dev/pts worked for me
umount /dev/pts
mount devpts /dev/pts -t devpts
Reference: http://www.iitk.ac.in/LDP/LDP/lfs/5.0/html/chapter06/proc.html
Just add these lines to your /etc/mtab and /etc/fstab, and reboot the system.
none /dev/pts devpts defaults 0 0
I had the exact same error trying to connect via ssh to my server. As I can see you're using a server provided by Hetzner connecting to it on port 22:
debug1: Connecting to xxx.your-server.de [188.40.3.15] port 22.
The offical wiki/documention from Hetzner says:
Protocol for encrypted remote diagnostics for servers/computers(consoles). The SSH port to be used is 222.
So you have to connect via port 222:
ssh -p 222 username@my-server.de
I solved a similar problem with one of our users who was used only for ssh port forwarding so he don't need to have access to PTY and it was prohibited in .ssh/authorized_keys file:
no-pty ssh-rsa AAA...nUB9 someuser
So when you tried to log in to this user, only message
PTY allocation request failed on channel 0
was returned. So check your user's authorized_keys file.
rebooting the instance from AWS console worked for me. There was a service that was leaking file connections that lsof helped find.
It's an old question, but if someone gets here like me...
This might be result of a wrong date in the server. If you are working with an embedded system this might be the cause... So check your date:
$ date
just found out, what was the problem in my case (provider strato): I had the same problem with output "shell request failed on channel 0" in the end.
I have to use the master password with the web-domain name as login. (In German www.wunschname.de, where wunschname is your web-address.)
A ssh login with sftp-user names and the corresponding passwords is without success. (Although scp and sftp works with these sftp users!)
shell request failed on channel 0
mean you don't have shell or remote commands access, fix your user permission on server to have shell access or if you just want tunneling use -N and -T options
Try this:
vi /etc/security/limits.d/20-nproc.conf
* soft nproc 4096 # change to 65535
root soft nproc unlimited
remounting /dev/pts works for me. you can do this remotely via ssh if you run ssh like this against the affected machine. ssh doesn't request a tty when running commands like this and therefore this will allow you to remount /dev/pts remotely
ssh user@host -- 'mount -o remount,rw /dev/pts'
I occasionally see this when spinning up a VM. Our automation system starts applying updates, so depending on timing can hit an update to critical packages.
Upshot - this might happen if ssh or other related packages are being updated on the destination machine.
I encountered this error while using my git bash. I was able to solve this by re-installing git for windows. More details in this answer.
I also faced the same issue. Just restarting my servers solved the issue.
来源：https://stackoverflow.com/questions/27021641/how-to-fix-request-failed-on-channel-0