After a recent macOS upgrade, some ssh access was strangely blocked. I turned on verbose logs to check the problem.
It is becoming pretty slow in SSH to a CentOS server.
Trying to print a verbose log:
$ ssh -vvvv my-host .... debug3: send packet: type 21 debug2: set_newkeys: mode 1 debug1: rekey out after 134217728 blocks debug1: SSH2_MSG_NEWKEYS sent debug1: expecting SSH2_MSG_NEWKEYS debug3: receive packet: type 21 debug1: SSH2_MSG_NEWKEYS received debug2: set_newkeys: mode 0 debug1: rekey in after 134217728 blocks debug1: Will attempt key: /Users/user/.ssh/id_rsa RSA SHA256:XXXXX/gNY explicit debug2: pubkey_prepare: done 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 ..... <<<-- long long long silence here debug3: receive packet: type 51 <<<-- and then continue to access the server debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password debug3: preferred publickey,keyboard-interactive,password
Bash script writing is a import approach to configure the linux system. Suppose we wish to add a user if not exists, the command may seems as follow:
TARGET_USER=alice if (! id -u $TARGET_USER > /dev/null 2>&1 ); then echo "creating user $TARGET_USER" # adduser $TARGET_USER fi
However, it is kind of too long. In this case short-circuiting is a alternative solution. (more…)
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