日拱一卒

SSH Tips

 
  • 2018年 10月19日
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不重启 ssh 服务并加载新的配置

After updated /etc/ssh/sshd_config, using below command to reload the sshd_config without restart sshd daemon service.

systemctl reload sshd

# 或
sudo kill -SIGHUP $(pgrep -f "sshd -D")

SSH 免密登录设置

chmod 755 ~/.ssh
chmod 600 ~/.ssh/authorized_keys

SSH 通过私钥生成公钥

ssh-keygen -y -f id_rsa > id_rsa.pub

生成 sshd 所需 host keys

启动 sshd 服务时如果没有 host keys，会报如下错误

sshd: no hostkeys available -- exiting.

执行以下命令生成所需的 host keys

ssh-keygen -A

SSH known host update

TARGET_HOST=[hostname or IP]

# Remove the old key(s) from known_hosts
ssh-keygen -R $TARGET_HOST

# Add the new key(s) to known_hosts (and also hash the hostname/address)
ssh-keyscan -H $TARGET_HOST >> ~/.ssh/known_hosts

Autossh

语法

autossh [-V] [-M port[:echo_port]] [-f] [SSH_OPTIONS]

远程登录

autossh -M 12345 -i .ssh/id_rsa remote-server

端口转发

autossh -M 12345 -o ServerAliveInterval=60 -o ServerAliveCountMax=10 -NT -L 0.0.0.0:8080:remote-server:8080 jump-server

查看 autossh 日志

# 使用环境变量将日志输出到指定文件路径，然后启动 autossh 后查看日志
export AUTOSSH_LOGFILE="$HOME/autossh.log"

autossh -M 10090 -D 10080 jump-server

SSH supported escape sequences

 ~.   - terminate connection (and any multiplexed sessions)
 ~B   - send a BREAK to the remote system
 ~C   - open a command line
 ~R   - request rekey
 ~V/v - decrease/increase verbosity (LogLevel)
 ~^Z  - suspend ssh
 ~#   - list forwarded connections
 ~&   - background ssh (when waiting for connections to terminate)
 ~?   - this message
 ~~   - send the escape character by typing it twice
(Note that escapes are only recognized immediately after newline.)

使用 PSSH 并行访问多台远程主机

-h HOST_FILE, --hosts=HOST_FILE
                      hosts file (each line "[user@]host[:port]")
-l USER, --user=USER  username (OPTIONAL)
-p PAR, --par=PAR     max number of parallel threads (OPTIONAL)
-A, --askpass         Ask for a password (OPTIONAL)
-x ARGS, --extra-args=ARGS
                      Extra command-line arguments, with processing for
                      spaces, quotes, and backslashes
-i, --inline          inline aggregated output and error for each server

pssh -x -q -i -h server-list -l root -A echo 'hello world.'

使用 SSH + TAR 实现远程备份或远程复制

将远程数据压缩后复制到本地

# 压缩remote-server上的/opt/app目录到标准输出，排除/opt/app目录下的logs目录和*.log文件
ssh user@remote-server 'tar czf - --exclude="logs" --exclude="*.log" /opt/app' > app.tar.gz

# 只打包应用所在目录
ssh user@remote-server 'tar czf - -C /opt --exclude="logs" --exclude="*.log" app' > app.tar.gz

将远程压缩文件解压到本地

ssh user@remote-server 'cd /opt; cat app.tar.gz' | tar xzvf - -C /opt

将本地数据压缩后备份到远程服务器

tar cvzf - -C /opt app | ssh user@remote-server 'cat > /opt/app.tar.gz'

scp 命令在进行远程复制时不会压缩数据，须使用 -C 选项开启压缩模式.

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