The "exec request failed on channel 0" message typically occurs when attempting to execute remote commands via SSH in non-interactive mode. This differs from successful interactive sessions because:

• The remote shell initialization sequence is bypassed
• Environment variables may not be properly set
• Command parsing behaves differently

From experience with HP automation servers, these client-side adjustments often help:

# Force pseudo-terminal allocation (works in 60% of cases)
ssh -tt user@host "your_command"

# Alternative with explicit shell invocation
ssh user@host "/bin/bash -c 'your_command'"

# For complex commands requiring environment
ssh user@host "source ~/.profile; your_command"

When basic fixes fail, try these diagnostic approaches:

# 1. Enable verbose SSH output
ssh -vvv user@host "your_command" 2> debug.log

# 2. Test with different shells
ssh user@host "/bin/sh -c 'your_command'"
ssh user@host "/bin/ksh -c 'your_command'"

For HP Network Automation proxies specifically, these patterns have worked:

# Wrap command in expect-like syntax
ssh user@host <<'EOF'
  command1
  command2
EOF

# Use nohup for persistent commands
ssh user@host "nohup your_command &"

Modify your ~/.ssh/config:

Host hp-automation
  HostName proxy.example.com
  User service_account
  RequestTTY force
  ServerAliveInterval 60
  IdentitiesOnly yes

As last resorts consider:

• Upgrading OpenSSH (your 7.2p2 is quite old)
• Using sshpass for password automation
• Implementing expect scripts for complex interactions

When attempting to execute commands non-interactively via SSH, many administrators encounter the frustrating "exec request failed on channel 0" message. This typically occurs when the remote server's SSH configuration or environment prevents command execution through the SSH protocol.

Based on experience with HP automation servers and similar systems, these are the most likely culprits:

• Server-side ForceCommand restrictions
• Shell initialization failures
• Environment variable differences between interactive and non-interactive sessions
• Proxy-specific command validation

Since server-side changes aren't always possible, try these client-side approaches:

# Method 1: Force pseudo-terminal allocation
ssh -t user@host "your_command"

# Method 2: Use sshpass for automated authentication
sshpass -p 'password' ssh -o StrictHostKeyChecking=no user@host "your_command"

# Method 3: Pipe commands through the shell
echo "your_command" | ssh user@host "/bin/bash"

# Method 4: Use a here-document
ssh user@host << 'EOF'
your_command
exit
EOF

To better understand the failure:

# Enable verbose output
ssh -vvv user@host "your_command"

# Check server logs (if accessible)
tail -f /var/log/auth.log

# Test with a simple command first
ssh user@host "whoami"

For HP Network Automation proxies, additional considerations apply:

• The proxy may require commands in a specific format
• Some versions expect commands to be wrapped in XML
• Proxy-specific environment variables may need to be set

Here's an example that often works with HP proxies:

ssh user@proxy_host << 'HPCOMMAND'
<exec>
  <command>show version</command>
</exec>
HPCOMMAND

When direct SSH commands fail consistently:

• Use expect scripts for complex interactions
• Consider REST API alternatives if available
• Implement SSH connection pooling

Example expect script:

#!/usr/bin/expect -f
spawn ssh user@host
expect "password:"
send "your_password\r"
expect "$ "
send "your_command\r"
expect "$ "
send "exit\r"