Recently a friend of mine, brought a new Laptop. He installed Red Hat Enterrpise Linux workstation 4.0. However, after installation he realized that he lost all his Mozilla thunderbird emails and Firefox bookmarks, chat client logs and other files.
I told him just copy all old files from /home/$you to a new system /home/$you directory. He was trying some age-old tutorial from net, which explains how to copy files using tar and restore it back to new system. During this procedure, he was messing up with file system permissions.
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This is Part III in a series on Execute Commands on Multiple Linux or UNIX Servers Simultaneously. The full series is Part I, Part II, and Part III.
In third and final part of this series I will cover expect tool. Expect is a program that talks to other interactive programs according to a script. Expect is useful for running any program which requires interaction between the program and the user. For example
Expect comes with special pre installed script called multixterm expect. If you are using Debian Linux then use apt-get as follows :
# apt-get install expect
# apt-get install expectk
If you are using Red hat Linux then use up2date command as follows:
# up2date -i expect
Fedora core (RHEL 5) / CentOS Linux user can use yum:
# yum install expect expectk
You can use ports to install expect under FreeBSD or use following command:
# pkg_add -v -r expect
Please note you can download expect from offical web site.
General syntax of multixterm:
multixterm -xc "command arg1 arg2" server1 server2...
Multixterm creates multiple xterms that can be driven together or separately so that you can execute or run on multiple hosts/servers simultaneously. The following command line starts up two xterms using ssh to the hosts 192.168.1.16 and 192.168.1.11:
$ multixterm -xc "ssh root@%n" 192.168.1.11 192.168.1.16
- -xc : The optional -xc argument indicates a command to be run in each named xterm (see -xn). With no -xc argument, the command is the current shell. This means you type command once and it get executed on both ssh hosts/servers.
- ssh root@%n : ssh is a command to connect remote server with root user. This name will also be substituted for any %n in the command argument.
Debian Linux stores multixterm at /usr/share/doc/expect directory. You need to type commands in multixterm window itself (stdin window). Click on stdin window and type uptime or w command:
For example when I typed the uptime and w command it looked like as follows:
Most of the time you login into remote server via ssh. If you start a shell script or command and you exit (abort remote connection), the process / command will get killed. Sometime job or command takes a long time. If you are not sure when the job will finish, then it is better to leave job running in background. But, if you log out of the system, the job will be stopped and terminated by your shell. What do you do to keep job running in the background when process gets SIGHUP?
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