[the second login need password]

.ssh/config as follows:

host log
        hostname 23.251.96.137
host *
        user walker.xia
        ServerAliveInterval 30
        GSSAPIAuthentication no
        ForwardAgent yes
        TCPKeepAlive no

the debug info for the bad situation:

debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0 /home/walkerxk/.ssh/id_rsa_2
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 535
debug2: input_userauth_pk_ok: fp SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
debug3: sign_and_send_pubkey: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
Enter passphrase for key '/home/walkerxk/.ssh/id_rsa_2':

the debug info for the good situation:

debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0 /home/walkerxk/.ssh/id_rsa_2
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 535
debug2: input_userauth_pk_ok: fp SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
debug3: sign_and_send_pubkey: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
debug3: send packet: type 50
debug3: receive packet: type 52
debug1: Authentication succeeded (publickey).
Authenticated to 23.251.96.137 ([23.251.96.137]:22).
debug1: channel 0: new [client-session]

 

[the second login need password]

i first login to the server without password, after the network broken, i login to the server again in the same panel in tmux. it ask for a password:

10:28:06#walkerxk@ubuntu1/~> ssh log date
Enter passphrase for key '/home/walkerxk/.ssh/id_rsa_2':
Wed Nov  7 02:28:15 UTC 2018
10:28:15#walkerxk@ubuntu1/~>

i open another panel  in tmux and login to the server, i don't ask for a password

10:28:09#walkerxk@ubuntu1/~> ssh log date
Wed Nov  7 02:28:13 UTC 2018
10:28:14#walkerxk@ubuntu1/~>

[keychain did't work in crontab]

script as follows:

#!/bin/bash
eval `keychain --noask --eval id_rsa_2`
ssh -vvv 192.254.80.9 date

i run it manually, it works:

ssh 192.254.80.9 date
Tue Nov  6 03:13:08 UTC 2018

crontab as follows:

15 11 6 11 2 bash -x /home/walkerxk/conf/a.sh >&/home/walkerxk/conf/a.dbg

crontab log as follows:

debug2: key: /home/walkerxk/.ssh/id_rsa_2 (0x55c0eaf6e150)
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
debug3: receive packet: type 51
debug1: Authentications that can continue: publickey
debug3: start over, passed a different list publickey
debug3: preferred publickey,keyboard-interactive,password
debug3: authmethod_lookup publickey
debug3: remaining preferred: keyboard-interactive,password
debug3: authmethod_is_enabled publickey
debug1: Next authentication method: publickey
debug1: Offering public key: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0 /home/walkerxk/.ssh/id_rsa_2
debug3: send_pubkey_test
debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 60
debug1: Server accepts key: pkalg rsa-sha2-512 blen 535
debug2: input_userauth_pk_ok: fp SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
debug3: sign_and_send_pubkey: RSA SHA256:ZfKfGXBW0BmGPoRg8rgpmSOgyHD9UZEpcpzhMdjUim0
debug1: read_passphrase: can't open /dev/tty: No such device or address
debug2: no passphrase given, try next key
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
walker.xia@192.254.80.9: Permission denied (publickey).

i tried add ". ~/.keychain/ubuntu1-sh" before eval command,it did't work too.

[how can i login the third server thought the second server did not not have the private key]

thanks, it works.

[how can i login the third server thought the second server did not not have the private key]

i have three servers:

server A:

have the public key and the private key

server B

have the public key

server C

have the public key.

i want to login from A to B and then login from B to C.

i have config ForwardAgent to yes both on server A and server B.