How to fix request failed on channel 0

Question

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- gt client aes128-ctr hmac-md5 none debug1  kex  client- gt server aes128-ctr hmac-md5 none debug1  SSH2 MSG KEX DH GEX REQUEST 1024 lt 1024 lt 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

User · Answer

rebooting the instance from AWS console worked for me  There was a service that was leaking file connections that lsof helped find

User · Answer

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

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As you already found the -T flag that create a PTY  I will just respond to the second part   shell request failed on channel 0  You should pass a command  ssh username my-server de -p 22 help  After reading back the manual here  https   www jenkins io doc book managing cli   I find it not really clear that it would not work without a command  But as stated by  U V   the ssh interface is not a console interface  rather a connection utility  So you need to pass a command    If someone from the  quot jenkins quot  team pass accross this post  it would be great that if we pass no command  the help would show up  -

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in my case  the SFTP server will reject your SSH connection

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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

User · Answer

try with option -NT ssh -NT

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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

User · Answer

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

User · Answer

I also faced the same issue  Just restarting my servers solved the issue

User · Answer

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

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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

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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

User · Answer

Try this   vi  etc security limits d 20-nproc conf            soft    nproc     4096     change to 65535  root       soft    nproc     unlimited

User · Answer

Just rebooting a AWS instance works for me to clear the error  shell request failed on channel 0

User · Answer

Just add these lines to your  etc mtab and  etc fstab  and reboot the system   none     dev pts    devpts    defaults    0    0

User · Answer

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

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This is what which helped me from the various answers provided    Try logging in as root  that will get you in most of the times Try logging in as a different user  it successful  it means that the problem is with a specific account  amp  it implies that there are some process es  already started by the problematic account which are consuming resources preventing login most likely no of processes  Increase the limit in  etc security limits d 20-nproc conf as mentioned by xmduhan above Try to ssh again  it should work

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Should a person find themselves reading this QA while they are trying to ssh into a NetGear ReadyNAS device  be sure that the  rsync only  checkbox is unchecked in the dialog box for the ssh service in the admin interface

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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

User · Answer

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

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This was happening when I was trying to use sudo on  ssh -t git github com after adding my local user s public key to github  Just a head s up to the google happy people like me

[ssh] How to fix request failed on channel 0

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