Linux requirements

This topic lists the requirements for a Linux® server to be captured and deployed by IBM® Cloud Infrastructure Center.

For the supported guest Linux distributions and root disk types on z/VM®, refer to Guest operating system support for z/VM

Note:
- SLES 15 SP2 cann't be installed directly on FBA disk type on z/VM for some known issue. To make an image using FBA as root disk type for SLES 15 SP2, you need to install SLES 15 SP1 on FBA disk first and upgrade to SLES 15 SP2, then capture this server into an image to be deployed by IBM Cloud Infrastructure Center.
The Linux server that is used as the source of the captured image should meet the following criteria:
- When creating images used to deploy virtual machines on ECKD or FBA disk, ECKD or FBA disks should be used as the root disk:
  - The root file system must not be on a logical volume.
  - Ensure that the image that is deployed via the IBM Cloud Infrastructure Center matches the disk type that is configured by the compute_disk_pool of /opt/ibm/icic/config.properties in the management node. Either a FBA or a ECKD image can be deployed on one compute node, but not both at the same time. The minidisk on which the root file system resides should be a minidisk of the same type, as required for a subsequent deployment (for example, an ECKD disk image should be captured for a subsequent deployment to an ECKD disk). And the disk should not be a full-pack minidisk, since cylinder 0 on a full-pack minidisks is reserved.
  - The virtual address of the root minidisk on the Linux server should be 0100. Otherwise the deployed virtual machine(VM) fails to start.
  - The root disk should have a single partition. For SLES 15 SP1 or SP2 server, when configuring the partition size, select the Custom Region option, modify the start block from 768 to 24 to make full use of the root disk.
- When creating images used to boot a virtual machine from volume, FC SAN volume should be used as the root disk:
  - When no LVM (Logical Volume Management) is involved, only one partition that is a standard root partition is supported.
  - LVM is supported with the following limitations:
    - Only two partitions are supported where the first one is a standard (non-LVM) partition mounted to / and the second one is a LVM physical volume.
    - /boot should reside on the / partition, instead of being a separate partition.
    - When deploying virtual machines from such an image to a larger disk, the LVM volume group is resized automatically. You need to manually extend one or many of the logical volumes after the virtual machine is up. How to extend the logical volume, taking RHEL 7 as an example, refer to Growing Logical Volumes.
    The following is an example of the supported disklayout when LVM is involved:
```
[root@redhat79 ~]# df -h
Filesystem                     Size  Used Avail Use% Mounted on
devtmpfs                       3.9G     0  3.9G   0% /dev
tmpfs                          3.9G     0  3.9G   0% /dev/shm
tmpfs                          3.9G  8.4M  3.9G   1% /run
tmpfs                          3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/mapper/mpatha1            3.0G  1.3G  1.7G  44% /
/dev/mapper/rootvg-homelv      125M  6.9M  118M   6% /home
/dev/mapper/rootvg-tmplv       509M   27M  483M   6% /tmp
/dev/mapper/rootvg-optlv       253M   14M  240M   6% /opt
/dev/mapper/rootvg-varlv       441M   65M  377M  15% /var
/dev/mapper/rootvg-vartmplv    125M  6.9M  118M   6% /var/tmp
/dev/mapper/rootvg-varloglv    509M   31M  479M   6% /var/log
/dev/mapper/rootvg-varauditlv   61M  3.5M   58M   6% /var/audit
tmpfs                          788M     0  788M   0% /run/user/0
[root@redhat79 ~]# pvs
PV                  VG     Fmt  Attr PSize  PFree
/dev/mapper/mpatha2 rootvg lvm2 a--  <2.00g    0
[root@redhat79 ~]#
[root@redhat79 ~]# vgs
VG     #PV #LV #SN Attr   VSize  VFree
rootvg   1   7   0 wz--n- <2.00g    0
[root@redhat79 ~]#
[root@redhat79 ~]# lvs
LV         VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
homelv     rootvg -wi-ao---- 128.00m
optlv      rootvg -wi-ao---- 256.00m
tmplv      rootvg -wi-ao---- 512.00m
varauditlv rootvg -wi-ao----  64.00m
varloglv   rootvg -wi-ao---- 512.00m
varlv      rootvg -wi-ao---- 444.00m
vartmplv   rootvg -wi-ao---- 128.00m
```
  Note:
  - If LVM is also used by the IBM Cloud Infrastructure Center management or compute node itself, ensure a different volume group name is used when creating an image.
- IBM Cloud Infrastructure Center supports only deploying an image to a disk larger or equal than the source image’s root disk size. Otherwise it would result in a loss of data. The image’s root disk size can be obtained by:
  - When the root disk is ECKD or FBA:
```
hexdump -C -n 64 <image_path>
```
  - When the root disk is volume:
```
qemu-img info <image_path>
```
  The virtual size in the output represents the size of the root disk. The following is an example for an image made from a server whose root disk size is 3.0G.
```
[root@tstcomp ~]# qemu-img info rhel77_scsi.qcow2
image: rhel77_scsi.qcow2
file format: qcow2
virtual size: 3.0G (3221225472 bytes)
disk size: 1.4G
cluster_size: 65536
Format specific information:
    compat: 1.1
    lazy refcounts: false
    refcount bits: 16
    corrupt: false
```