hosts

For hosts with multiple IP addresses and different official host names configured at the system level, this file associates the host names and IP addresses in LSF.

By default, LSF assumes each host in the cluster:

Has a unique official host name
Can resolve its IP address from its name
Can resolve its official name from its IP address

Hosts with only one IP address, or hosts with multiple IP addresses that already resolve to a unique official host name should not be configured in this file: they are resolved using the default method for your system (for example, local configuration files like /etc/hosts or through DNS.)

The LSF hosts file is used in environments where:

Machines in cluster have multiple network interfaces and cannot be set up in the system with a unique official host name
DNS is slow or not configured properly
Machines have special topology requirements; for example, in HPC systems where it is desirable to map multiple actual hosts to a single head end host

The LSF hosts file is not installed by default. It is usually located in the directory specified by LSF_CONFDIR. The format of LSF_CONFDIR/hosts is similar to the format of the /etc/hosts file on UNIX machines.

hosts file structure

One line for each IP address, consisting of the IP address, followed by the official host name, optionally followed by host aliases, all separated by spaces or tabs. Each line has the form:

ip_address official_name [alias [alias ...]]

IP addresses can have either a dotted quad notation (IPv4) or IP Next Generation (IPv6) format. You can use IPv6 addresses if you define the parameter LSF_ENABLE_SUPPORT_IPV6 in lsf.conf; you do not have to map IPv4 addresses to an IPv6 format.

Use consecutive lines for IP addresses belonging to the same host. You can assign different aliases to different addresses.

Use a pound sign (#) to indicate a comment (the rest of the line is not read by LSF). Do not use #if as this is reserved syntax for time-based configuration.

IP address

Written using an IPv4 or IPv6 format. LSF supports both formats; you do not have to map IPv4 addresses to an IPv6 format (if you define the parameter LSF_ENABLE_SUPPORT_IPV6 in lsf.conf).

IPv4 format: nnn.nnn.nnn.nnn
IPv6 format: nnnn:nnnn:nnnn:nnnn:nnnn:nnnn:nnnn:nnnn

Official host name

The official host name. Single character names are not allowed.

Specify -GATEWAY or -GW as part of the host name if the host serves as a GATEWAY.

Specify -TAC as the last part of the host name if the host is a TAC and is a DoD host.

Specify the host name in the format defined in Internet RFC 952, which states:

A name (Net, Host, Gateway, or Domain name) is a text string up to 24 characters drawn from the alphabet (A-Z), digits (0-9), minus sign (-), and period (.). Periods are only allowed when they serve to delimit components of domain style names. (See RFC 921, Domain Name System Implementation Schedule, for background). No blank or space characters are permitted as part of a name. No distinction is made between upper and lower case. The first character must be an alpha character. The last character must not be a minus sign or a period.

RFC 952 has been modified by RFC 1123 to relax the restriction on the first character being a digit.

For maximum interoperability with the Internet, you should use host names no longer than 24 characters for the host portion (exclusive of the domain component).

Aliases

Optional. Aliases to the host name.

The default host file syntax

ip_address official_name [alias [alias ...]]

is powerful and flexible, but it is difficult to configure in systems where a single host name has many aliases, and in multihomed host environments.

In these cases, the hosts file can become very large and unmanageable, and configuration is prone to error.

The syntax of the LSF hosts file supports host name ranges as aliases for an IP address. This simplifies the host name alias specification.

To use host name ranges as aliases, the host names must consist of a fixed node group name prefix and node indices, specified in a form like:

host_name[index_x-index_y, index_m, index_a-index_b]

For example:

atlasD0[0-3,4,5-6, ...]

is equivalent to:

atlasD0[0-6, ...]

The node list does not need to be a continuous range (some nodes can be configured out). Node indices can be numbers or letters (both upper case and lower case).

For example, some systems map internal compute nodes to single LSF host names. A host file might contains 64 lines, each specifying an LSF host name and 32 node names that correspond to each LSF host:

...
177.16.1.1 atlasD0 atlas0 atlas1 atlas2 atlas3 atlas4 ... atlas31
177.16.1.2 atlasD1 atlas32 atlas33 atlas34 atlas35 atlas36 ... atlas63
...

In the new format, you still map the nodes to the LSF hosts, so the number of lines remains the same, but the format is simplified because you only have to specify ranges for the nodes, not each node individually as an alias:

...
177.16.1.1 atlasD0 atlas[0-31]
177.16.1.2 atlasD1 atlas[32-63]
...

You can use either an IPv4 or an IPv6 format for the IP address (if you define the parameter LSF_ENABLE_SUPPORT_IPV6 in lsf.conf).

IPv4 Example

192.168.1.1 hostA hostB
192.168.2.2 hostA hostC host-C

In this example, hostA has 2 IP addresses and 3 aliases. The alias hostB specifies the first address, and the aliases hostC and host-C specify the second address. LSF uses the official host name, hostA, to identify that both IP addresses belong to the same host.

IPv6 Example

3ffe:b80:3:1a91::2 hostA hostB 3ffe:b80:3:1a91::3 hostA hostC host-C