Operating Systems

Updating the user_volume_include statement. z/VM uses the user_volume_include statement to attach disk devices to the system at Initial Program Load (IPL) based on the volume identifier (partition name in Linux terms). The volume identifier is a volume serial number that’s up to six characters. As the Linux on System z environment grows, adding disk incrementally can be tedious. By using this statement with a wildcard, new disks will be automatically attached and available for the Linux guests at IPL.

Editing the features statement. Here are recommended FEATURES statement changes (see Figure 2):

• Disconnect_timeout off keeps the Linux guest running and won’t shut down the guest if you disconnect the console. Without this set, the guest will be automatically shut down on a disconnect. A continuously active guest will never be forced off the system.
• VDISK is recommended for a Linux swap device. You should provide Linux a tiered SWAP subsystem where the first device is a small (less than 512MB) VDISK in memory. If that isn’t enough, back it up with a dedicated disk volume or minidisk of appropriate size.
• Syslim and userlim are set to infinite to allow flexibility of VDISK size for each guest. Some Linux guests might only need 512MB of SWAP; others might need more.

Common Linux Default Profile

A common default profile in the USER DIRECT file will greatly simplify administration and is less error-prone than individually modifying the basic parameters for each Linux guest (see Figure 3). The MACH ESA statement will limit the number of virtual CPUs you can define for a particular virtual machine. To install Linux, you will need the READER, PUNCH, SPOOL, and other devices.

Shared Linux Files

You should have all the kernels, initrd, and parm files on one guest that can be shared in read-only mode with the other guests you need to create. That way, you only have to use File Transfer Protocol (FTP) once to send the files to the shared guest instead of every time you need to create a new guest. Once that guest is created, the files are shared with the other Linux guests via link statements in the guest’s PROFILE EXEC. LNXADMIN is a good name to choose for this shared guest; LNXADM is a good name for the volume identifier in the MDISK statement.
 
Linux Profile Exec

After the LNXADMIN guest is set up and the 191 minidisk is formatted, create a profile exec as shown in Figure 4. The CP LINK statement is assigning its 191 as 391. The other Linux guests that are created will have the kernel, parm, and initrd available to them as 391 and accessed as B after this profile exec is copied to the new Linux guest’s 191 disk.

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