What does the Broken pipe message mean in an SSH session?
Sometimes my SSH session disconnects with a
Write failed: Broken pipe message. What does it mean? And how can I keep my session open?
I know about
screen, but that’s not the answer I’m looking for. I think this is a
sshd config option.
It usually means that your network (TCP) connection was reset. E.g. your internet provider reconnected you or something like this.
It’s possible that your server closes connections that are idle for too long.
You can update either your client (
ServerAliveInterval) or your server (
ServerAliveInterval Sets a timeout interval in seconds after which if no data has been received from the server, ssh(1) will send a message through the encrypted channel to request a response from the server. The default is 0, indicating that these messages will not be sent to the server. This option applies to protocol version 2 only. ClientAliveInterval Sets a timeout interval in seconds after which if no data has been received from the client, sshd(8) will send a message through the encrypted channel to request a response from the client. The default is 0, indicating that these messages will not be sent to the client. This option applies to protocol version 2 only.
To update your server (and restart your
echo "ClientAliveInterval 60" | sudo tee -a /etc/ssh/sshd_config
echo "ServerAliveInterval 60" >> ~/.ssh/config
Another cause for the “Broken Pipe message” is that another machine is attempting use the same IP as your host.
A simple way to test if someone else is using that IP:
- Turn off your host
- ping the same IP to see if another machine is using that IP
To find out which machines are on your network, you can use this Unix & Linux question title: How to find what other machines are connected to the local network.
An alternative solution would be to use
mosh – the mobile shell. In contrast to ssh it connects via UDP and supports roaming. You can start your session at home, suspend your laptop, take it to work / friends / wherever else you have internet, unsuspend your laptop and continue to work as if nothing has happened. It is especially useful if you are on a lousy internet connection: It shows instant feedback if your keystrokes don’t reach the server and continuously tries to reestablish the connection.
Installation and setup are simple: It is now included in all current Linux (plus a few non-Linux) distributions and it coordinates the session initialization and authentication via a prior ssh connection. So if you are able to connect via
ssh user@server you are very likely to be able to connect with mosh just by calling
mosh user@server, if the mosh packages are installed on both ends.
The main reason for connection failures is that you have to reach the server on a UDP port (default range: 60000-61000) for mosh to work. So if the server is behind a firewall you are mostly out of luck if can’t punch holes in it yourself (security implications).
If you want to have a longer connection period, in the client add:
echo 'ServerAliveInterval 30' | tee -a ~/.ssh/config echo 'ServerAliveCountMax 1200' | tee -a ~/.ssh/config
ServerAliveCountMax by default this is set to 3. Therefore once the
ServerAliveInterval has sent 3 small packs of info to your server it will then automatically log out. Setting it to 1200 means this process will have to occur at least 1200 times. In short you should be connected at least 30*1200 seconds (10 hours).
I had the same problem but it is not as expected. If you find that on the same network another server is trying for the same IP address, you will face the same problem.
To solve this you need to check if there are other servers which use your same IP address. This can be done using the
I am using Debian so here is a sample of the commands that I use to determine if another server was indeed using the same IP address
apt-get install arp-scan arp-scan -I eth0 -l | grep 192.168.1.42 192.168.1.42 d4:eb:9a:f2:11:a1 (Unknown) 192.168.1.42 f4:23:a4:38:b5:76 (Unknown) (DUP: 2)
You will notice two sets of mac address using the same IP address. Avoid conflict by setting one to another IP address.
You can use SSH/SCP argument ‘
-o‘ to accomplish that, no need to set your (if you’re admin) server’s ssh-config.
SSH options related to keeping connection alive are
Basically, it goes like this:
% ssh -o TCPKeepAlive=yes -o ServerAliveCountMax=20 -o ServerAliveInterval=15 email@example.com
, to have the client sending "keep-alive" messages every 15 seconds until the limit of 20 messages — which amounts to
20 x 15 seconds = 5 minutes –, at which point the connection is considered broken/dead. The client process ends.
The man pages will give you more, detailed information:
I spent lots of time messing with ServerAliveInterval and ClientAliveInterval variables with no joy.
Finally, after comparing with a machine that did not have the broken pipe problem, I found the directive at the bottom of
Putting this at the bottom of my problem server’s
/etc/ssh/sshd_config did the trick.
Verified for Ubuntu 20.04.1 LTS, Ubuntu 16.04.7 LTS.
For me this was because I had used
ChrootDirectory which requires that the entire path given be owned by root (which it was not for me). Changing the permissions for the path and restarting sshd fixed the problem.