我试图自动化ssh连接。主要目标 - 避免被问及密码短语。这是ssh命令：
#!/bin/bash
chmod 600 ssh_key
chmod +x passhrase_script.sh
DISPLAY=":0" SSH_ASKPASS="passhrase_script.sh"
ssh -i ssh_key -F /dev/null -o UserKnownHostsFile=/dev/null -o StrictHostKeyChecking=no "$@"
适用于Ubuntu（OpenSSH_6.6.1，OpenSSL 1.0.1f 2014年1月6日）并且不适用于CentOS（OpenSSH_5.3p1，OpenSSL 1.0.1e-fips 2013年2月11日）
调试输出：
`OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /dev/null
debug2: ssh_connect: needpriv 0
debug1: Connecting to xxx [172.20.240.99] port 2222.
debug1: Connection established.
debug3: Not a RSA1 key file /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/ssh_key_8.
debug2: key_type_from_name: unknown key type '-----BEGIN'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'Proc-Type:'
debug3: key_read: missing keytype
debug2: key_type_from_name: unknown key type 'DEK-Info:'
debug3: key_read: missing keytype
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug3: key_read: missing whitespace
debug2: key_type_from_name: unknown key type '-----END'
debug3: key_read: missing keytype
debug1: identity file /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/ssh_key_8 type -1
debug1: identity file /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/ssh_key_8-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug2: fd 3 setting O_NONBLOCK
debug1: SSH2_MSG_KEXINIT sent
debug3: Wrote 960 bytes for a total of 981
debug1: SSH2_MSG_KEXINIT received
debug2: kex_parse_kexinit: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa-cert-v01@openssh.com,ssh-dss-cert-v01@openssh.com,ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc,cast128-cbc,aes192-cbc,aes256-cbc,arcfour,rijndael-cbc@lysator.liu.se
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512,hmac-ripemd160,hmac-ripemd160@openssh.com,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit: none,zlib@openssh.com,zlib
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: kex_parse_kexinit: ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2: kex_parse_kexinit: ssh-rsa,ssh-dss
debug2: kex_parse_kexinit: aes128-ctr,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc
debug2: kex_parse_kexinit: aes128-ctr,arcfour128,aes128-cbc,3des-cbc,blowfish-cbc
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha2-512,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: hmac-md5,hmac-sha1,hmac-sha2-256,hmac-sha2-512,hmac-sha1-96,hmac-md5-96
debug2: kex_parse_kexinit: none
debug2: kex_parse_kexinit: none
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit:
debug2: kex_parse_kexinit: first_kex_follows 0
debug2: kex_parse_kexinit: reserved 0
debug2: mac_setup: found hmac-md5
debug1: kex: server->client aes128-ctr hmac-md5 none
debug2: mac_setup: found hmac-md5
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug3: Wrote 24 bytes for a total of 1005
debug2: dh_gen_key: priv key bits set: 138/256
debug2: bits set: 518/1024
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug3: Wrote 144 bytes for a total of 1149
debug3: put_host_port: [172.20.240.99]:2222
debug3: put_host_port: [xxx]:2222
debug3: check_host_in_hostfile: host [xxx]:2222 filename /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host [xx]:2222 filename /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host [xx]:2222 filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host [xx]:2222 filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host [172.20.240.99]:2222 filename /vcs-hosting/tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host [172.20.240.99]:2222 filename /vcs-hosting/tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host [172.20.240.99]:2222 filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host [172.20.240.99]:2222 filename /etc/ssh/ssh_known_hosts
debug1: checking without port identifier
debug3: check_host_in_hostfile: host xxx filename //tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host xxx filename /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host xxx filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host xxx filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host 172.20.240.99 filename /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host 172.20.240.99 filename /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/known_hosts_8
debug3: check_host_in_hostfile: host 172.20.240.99 filename /etc/ssh/ssh_known_hosts
debug3: check_host_in_hostfile: host 172.20.240.99 filename /etc/ssh/ssh_known_hosts
Warning: Permanently added '[xxx]:2222,[172.20.240.99]:2222' (RSA) to the list of known hosts.
debug2: bits set: 526/1024
debug1: ssh_rsa_verify: signature correct
debug2: kex_derive_keys
debug2: set_newkeys: mode 1
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: Wrote 16 bytes for a total of 1165
debug2: set_newkeys: mode 0
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug3: Wrote 48 bytes for a total of 1213
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug2: key: /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/ssh_key_8 ((nil))
debug3: Wrote 64 bytes for a total of 1277
debug1: Authentications that can continue: keyboard-interactive,publickey
debug3: start over, passed a different list keyboard-interactive,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: Trying private key: /tests/tests-war-loader-impl/build/apps/slave/temp/repo/project-44-1473687324554/git-temp/ssh_key_8
debug1: PEM_read_PrivateKey failed
debug1: read PEM private key done: type <unknown>
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
debug3: authmethod_lookup keyboard-interactive
debug3: remaining preferred: password
debug3: authmethod_is_enabled keyboard-interactive
debug1: Next authentication method: keyboard-interactive
debug2: userauth_kbdint
debug2: we sent a keyboard-interactive packet, wait for reply
debug3: Wrote 96 bytes for a total of 1373
debug1: Authentications that can continue: keyboard-interactive,publickey
debug3: userauth_kbdint: disable: no info_req_seen
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
Permission denied (keyboard-interactive,publickey)`
你可以看到它最后说debug2: no passphrase given, try next key。 SSH_ASKPASS已设置且工作正常