我正在使用 bash 自动执行一系列 ssh 命令，并在从命令行调用脚本时让它们工作。下面是脚本中 ssh 调用的示例。
ssh-keyscan -H $CURRENT_IP >> ~/.ssh/known_hosts
sshpass -f pass.txt ssh -o ConnectionAttempts=3 -o ConnectTimeout=10 $login exit
但是，我添加了一个 cronjob 每天运行一次脚本，但遇到了 ssh 命令无法正确执行的问题。我已阅读此问题，这是 ssh 和 crontab 的已知问题，因为 crontab 无法检索密钥或其他内容。我遵循了其他一些问题的建议，最终得到了 ssh 调用。
ssh-keyscan -H $CURRENT_IP >> ~/.ssh/known_hosts
sshpass -f pass.txt ssh -i ~/.ssh/known_hosts -o ConnectionAttempts=3 -o ConnectTimeout=10 $login exit
我认为使用 -i 标志可以解决我的问题，但后来我开始收到以下错误。
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ WARNING: UNPROTECTED PRIVATE KEY FILE! @
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Permissions 0644 for '/root/.ssh/known_hosts' are too open.
It is required that your private key files are NOT accessible by others.
This private key will be ignored.
为了解决这个问题，我尝试了一下，chmod 400 /root/.ssh/known_hosts这消除了错误。然而，这随后产生了一个问题，即 ssh 连接将无限期挂起，尽管有连接超时和尝试限制。
有没有办法在更改密钥文件的权限后停止挂起连接？或者至少，有没有一种在 crontab 中使用 ssh 的方法确实有效？
机器是Ubuntu 16.04。
先谢谢了。
编辑：这是在挂起的 ssh 上使用 -v 标志生成的日志
OpenSSH_7.2p2 Ubuntu-4ubuntu2.4, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "x.x.x.x" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to x.x.x.x [x.x.x.x] port 22.
debug2: fd 3 setting O_NONBLOCK
debug1: fd 3 clearing O_NONBLOCK
debug1: Connection established.
debug3: timeout: 9999 ms remain after connect
debug1: permanently_set_uid: 0/0
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/known_hosts type -1
debug1: key_load_public: No such file or directory
debug1: identity file /root/.ssh/known_hosts-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.4
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.4 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to x.x.x.x:22 as 'user'
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /root/.ssh/known_hosts:1
debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:2
debug3: record_hostkey: found key type ED25519 in file /root/.ssh/known_hosts:3
debug3: load_hostkeys: loaded 3 keys from x.x.x.x
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug3: send packet: type 20
debug1: SSH2_MSG_KEXINIT sent
debug3: receive packet: type 20
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos:
debug2: languages stoc:
debug2: first_kex_follows 0
debug2: reserved 0
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug3: send packet: type 30
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug3: receive packet: type 31
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:6GY6MDJn0TC3fXnid2v8CJIe918ZFkC6yxQ+jugNUwE
debug3: hostkeys_foreach: reading file "/root/.ssh/known_hosts"
debug3: record_hostkey: found key type ECDSA in file /root/.ssh/known_hosts:1
debug3: record_hostkey: found key type RSA in file /root/.ssh/known_hosts:2
debug3: record_hostkey: found key type ED25519 in file /root/.ssh/known_hosts:3
debug3: load_hostkeys: loaded 3 keys from x.x.x.x
debug1: Host 'x.x.x.x' is known and matches the ECDSA host key.
debug1: Found key in /root/.ssh/known_hosts:1
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /root/.ssh/known_hosts ((nil)), explicit
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,password,keyboard-interactive
debug3: start over, passed a different list publickey,password,keyboard-interactive
debug3: preferred gssapi-keyex,gssapi-with-mic,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: /root/.ssh/known_hosts