Mosh
Mosh is an alternative SSH terminal. It has support for roaming, local echo and uses UDP for transport. It also aims to improve responsiveness on intermittent, and high latency connections.
See the mosh Package and mosh Options
Instalation
Client
Install the mosh package.
Server
Enable the programs.mosh module. You can simply add the following into your /etc/nixos/configuration.nix:
# Enable mosh, the ssh alternative when client has bad connection
# Opens UDP ports 60000 ... 61000
programs.mosh.enable = true;
Usage
With mosh installed on both the client and server, connect by running:
$ mosh user@server
Note that mosh uses SSH for authentication and initialization, so it will respect aliases and other options in .ssh/config. You can also specify SSH options using the --ssh argument. For example, to use port 1122 instead of 22, you can either use Port 1122 in SSH config, or use mosh with the --ssh argument:
$ mosh --ssh='ssh -p 1122' user@server
More information is available at mosh.org or using man mosh
Troubleshooting
Missing /run/user/1000
Using a mosh session, $XDG_RUNTIME_DIR (/run/user/1000) doesn't exist and causes issues such as:
- nix-shell failing with
Error in tempdir() using /run/user/1000/nix-shell.XXXXX
This is caused by the way mosh handles logging-in to the system, the login is actually handled by a short ssh session, which ends immediately. logind, as it is used, closes the user's session and cleans up behind, since there is no lingering configured by default.
To enable lingering use:
$ loginctl enable-linger $USER
Then reconnect with mosh. Note that lingering is enabled by default in NixOS >= 16.09.
As a workaround, it is also possible to set an alias in the user's shell on the server wrapping mosh-server to keep the session around.
[1]
alias mosh-server = "systemd-run --user --scope mosh-server"
See also https://github.com/NixOS/nixpkgs/issues/3702#issue-40762878
The locale requested by LANG=*** isn't available here.
This error occurs when trying to connect to a linux server (non-NixOS distribution) on which mosh-server has been installed via nix. The easy solution is to set LOCALE_ARCHIVE to your OS locale-archive in your .profile or .zshenv:
export LOCALE_ARCHIVE=/usr/lib/locale/locale-archive