SEQ(1)

NAME
rseq - run a command on a cluster in sequence

SYNOPSIS
rseq [-aeiqtv] [-g rungroup1,...,rungroupN] [-l username] [-o porttimeout] [-p portnum] [-w node1,...,nodeN] [-x node1,...,nodeN] [command ...]

DESCRIPTION
The rseq utility can be used to run a command, or group of commands on a cluster of machines. The command or commands are run on a single node in the cluster, which is incremented in sequence on each invocation of rseq The following options are available:

-a  The -a option modifies the behavior of rseq when dealing with stdin. Normally all commands from stdin are run on the same machine. Specifying the -a option causes each command to be run on the next node in the seqence.

-e  Unless the -e option is specified, stderr from remote commands will not be reported to the user.

-i  The -i option will list information about the current cluster, and command groupings. It will also show you which command you are about to run, and your username if specified with the -l option.

-q  The -q option does not issue any commands, but displays information about the cluster.

-v  Prints the version of ClusterIt to the stdout, and exits.

-g  If the -g option is specified, followed by a comma separated list of group names, the command will only be run on that group of nodes. A node may be a part of more than one group if desired, however running without the -g option will run the command on the same node as many times as it appears in the file specified by the CLUSTER environment variable. This option is silently ignored if used with the -w option.

-l  If the -l option is specified, followed by a username, the commands will be run under that userid on the remote machines. Consideration must be taken for proper authentication, for this to work.

-o  The -o option is used to set the timeout in seconds to be used when testing remote connections. The default is five seconds.

-p  The -p option can be used to set the port number that testing should occur on when testing remote connections. The default behavior is to guess based on the remote command name.

-t  The -t option causes rseq to attempt a connection test to each node prior to attempting to run the remote command. If the test fails for any reason, the remote command will not be attempted. This can be useful when clusterfiles have suffered bitrot and some nodes no longer exist, or might be down for maintenance. The default timeout is 5 seconds. The timeout can be changed with the -o option. rseq will attempt to guess the port number of the remote service based on your RCMD_CMD setting. It knows about ssh and rsh. If rseq fails to guess your port correctly, you may use the -p argument to set the remote port number. If the RCMD_TEST environment variable exists, the testing will automatically take place.

-w  If the -w option is specified, followed by a comma delimited list of machine names, the command will be run on each node in the list. Without this option, rseq runs on the nodes listed in the file pointed to by the CLUSTER environment variable.

-x  The -x option can be used to exclude specific nodes from the cluster. The format is the same as the -w option, a comma delimited list of machine names. This option is silently ignored if used with the -w option.

ENVIRONMENT
rseq utilizes the following environment variables.

CLUSTER
    Contains a filename, which is a newline separated list of nodes in the cluster.

RCMD_CMD
    Command to use to connect to remote machines. The command chosen must be able to connect with no password to the remote host. Defaults to ssh.

RCMD_CMD_ARGS
    Arguments to pass to the remote shell command. Defaults to none.

RCMD_USER
    The username to connect to remote machines as by default.

SEQ_FILE
    Specifies a specific sequence file. This is a temporary file, which saves the number of the last node run on. It defaults to ‘/tmp/[pid].seq’. Where [pid] is the pid of the parent process of seq. It may be useful to wire the SEQ_FILE to a particular file, in order to keep proper sequence when invoking rseq from subshells or scripts.

RCMD_PORT
    The port number used to test remote connections. See the -p flag.

RCMD_TEST
    When set, rseq will automatically test all hosts before launching the remote command. See the -t option for more information.

RCMD_TEST_TIMEOUT
    The timeout in seconds to use when testing for remote connections.

DIAGNOSTICS
Exit status is 0 on success, 1 if an error occurs.

SEE ALSO
dsh(1), rsh(1), kerberos(3), hosts.equiv(5), rhosts(5)

HISTORY
The rseq command appeared in clusterit 1.1.

AUTHOR
Seq was written by Tim Rightnour.

BUGS
The rseq command works fine when used with the -w and -x flags. However the user may find that if the arguments are changed, or the flags are omitted on a subsequent run, the next node picked may not be predictable. The sequence is calculated on each invocation of rseq and the sequence numbers recorded in the temporary file may not match up to a new sequence placed on the command line.