Download of the Day: OpenSSH Server 5.0 ( security fix release )

Posted on in Categories Data recovery, Howto, Linux, Networking, OpenBSD, Security, UNIX last updated April 8, 2008

OpenSSH Logo
One of the most popular remote server management service has just released security fix version. This version avoid possible hijacking of X11-forwarded connections by refusing to listen on a port unless all address families bind successfully. You can download OpenSHH Server from official project web site or wait for your distro to release updated version.

Running Commands on a Remote Linux / UNIX Host

Posted on in Categories CentOS, Debian Linux, FreeBSD, Gentoo Linux, Howto, HP-UX, Linux, Monitoring, Networking, OpenBSD, OS X, RedHat/Fedora Linux, Security, Shell scripting, Solaris, Tips, Ubuntu Linux, UNIX last updated July 25, 2005

You would like to execute a command on a remote Linux/FreeBSD/Solaris/UNIX host and have the result displayed locally. Once result obtained it can be used by local script or program. A few examples:
=> File system and disk information

=> Get user information

=> Find out all running process

=> Find out if particular service is running or not etc

You can use rsh or ssh for this purpose. However, for security reason you should always use the ssh and NOT rsh. Please note that remote system must run the OpenSSH server.

Syntax for running command on a remote host:
ssh [USER-NAME]@[REMOTE-HOST] [command or script]

Where,

  • ssh: ssh (SSH client) is a program for logging into a remote machine and for executing commands on a remote machine.
  • USER-NAME: Remote host user name.
  • REMOTE-HOST: Remote host ip-address or host name, such as fbsd.cyberciti.biz.
  • command or script: Command or shell script is executed on the remote host instead of a login shell.

Examples

(A) Get disk information from a server called www1.cyberciti.biz:
$ ssh [email protected] df -h

(B) List what ports are open on remote host
$ ssh [email protected] netstat -vatn

(C) Reboot remote host:
$ ssh [email protected] reboot

(D) Restart mysql server (please note enclosed multiple command line arguments using a single or double quotes)
$ ssh [email protected] '/etc/init.d/mysql restart'

(E) Get memory information and store result/output to local file /tmp/memory.status:
$ ssh [email protected] 'free -m' > /tmp/memory.status

(G) You can also run multiple command or use the pipes, following command displays memory in format of “available memory = used + free memory” :
$ ssh [email protected] free -m | grep "Mem:" | awk '{ print "Total memory (used+free): " $3 " + " $4 " = " $2 }'

See how to configure ssh for password less login using public key based authentication.

=> Related: shell script to get uptime, disk usage, cpu usage, RAM usage,system load,etc. from multiple Linux servers and output the information on a single server in a html format.