AIS > Q and A to and from AI

2 Get IP #

get my ip v4 via cli
ip a|grep inet -m1|cut foooo

u got shoerter idea

Yep — much shorter and cleaner 👍 Here are good CLI one-liners, from most correct to shortest.

3 Best (IPv4, non-loopback, actually usable) #

1ip -4 addr show scope global | awk '{print $2}' | cut -d/ -f1

3 Very short (still sane) #

1ip -4 a | grep -oP '(?<=inet\s)\d+(\.\d+){3}' | head -n1

3 If you want the IP used for outbound traffic (often what you want) #

This is usually the best answer in practice:

1ip route get 1.1.1.1 | awk '{print $7}'

(doesn’t actually send traffic)

3 Ultra-short (but hacky) #

1hostname -I | awk '{print $1}'

⚠️ May return multiple IPs, ordering not guaranteed.

TL;DR #

If you just want the LAN IP to give your phone:

1ip route get 1.1.1.1 | awk '{print $7}'

If you want, I can give a POSIX-only version or one that excludes Docker / VPN interfaces.

.

2 SSH : ssh-add / ssh-agent #

Agent signature failed for id_ed25519: agent refused operation

That error is from SSH and means your SSH client tried to use a key via ssh-agent, but the agent refused to sign the request.

Agent signature failed for id_ed25519: agent refused operation

This is usually caused by one of the following. I’ll list them from most common → least, with fixes.

3 1. SSH agent is running, but the key is not loaded #

Check what keys the agent has:

1ssh-add -l

If you see:

• The agent has no identities. → this is the issue

Fix:

1ssh-add ~/.ssh/id_ed25519

Then retry your SSH command.

3 2. Key requires confirmation (macOS / security prompt blocked) #

On macOS, keys added with Keychain or Touch ID can silently fail if confirmation was denied or timed out.

Fix (macOS):

1ssh-add -K ~/.ssh/id_ed25519

If prompted, approve Touch ID / password.

You can also restart the agent:

1killall ssh-agent
2eval "$(ssh-agent -s)"
3ssh-add ~/.ssh/id_ed25519

3 3. SSH agent forwarding issue (very common on servers) #

If you’re SSH’ing from one machine into another and then trying to SSH again:

• Agent forwarding may be broken or not allowed

Check if forwarding is enabled:

1echo $SSH_AUTH_SOCK

If empty → agent not forwarded.

Fix (from your local machine):

1ssh -A user@host

Or in ~/.ssh/config:

1Host *
2  ForwardAgent yes

⚠️ Only do this for trusted hosts.

3 4. Key permissions are wrong #

SSH is strict about permissions.

1chmod 700 ~/.ssh
2chmod 600 ~/.ssh/id_ed25519
3chmod 644 ~/.ssh/id_ed25519.pub

Then reload the key:

1ssh-add -D
2ssh-add ~/.ssh/id_ed25519

3 5. Corrupted or incompatible key #

Test the key directly (bypassing agent):

1ssh -i ~/.ssh/id_ed25519 user@host

If this fails, the key itself may be invalid or not authorized on the server.

3 6. Using a restricted environment (Docker, WSL, CI, sudo) #

Some environments cannot access your SSH agent.

Examples:

• sudo without -E
• Docker without SSH_AUTH_SOCK mounted
• CI runners

Quick test:

1ssh-add -l

If it errors → agent inaccessible.

3 Quick “fix everything” reset #

1eval "$(ssh-agent -s)"
2ssh-add ~/.ssh/id_ed25519
3ssh user@host