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[Xen-users] create C7 domU from C6 dom0 using kickstart (trick)

  • To: Xen-users <xen-users@xxxxxxxxxxxxx>
  • From: Mark Pryor <tlviewer@xxxxxxxxx>
  • Date: Fri, 13 Feb 2015 05:35:53 +0000 (UTC)
  • Delivery-date: Fri, 13 Feb 2015 05:37:09 +0000
  • List-id: Xen user discussion <xen-users.lists.xen.org>

If you want your C7 domU on the ext4 filesys, you will run into trouble using the pygrub bootloader or trying to
e2fsck your domU partition from C6 dom0.

The reason is 2 fold: in the above tinyURL  you can see the patch where
RHEL7 drank the kool-aid and added a mke2fs flag used by no other Linux distro. They are singular in this setting.
The other reason is C6 doesn't have this flag available. So C6 ext4 is limited to 16TB partition size.

To workaround this, you need to coax the C7 installer to drop this `64bit` flag. You can do it in a ks pre-install script.
At the top of your ks script add:
------------- c7-ks.cfg -----------
alias mkfs.ext4='mkfs.ext4 -O ^64bit'
sed -i -e 's/,64bit$//' /etc/mke2fs.conf
------------ snip -------

Here's the xl cfg I used to do the pv install
cat tackc7.cfg
------------- tackc7.cfg ------------
disk=['file:/data4/cent7/CentOS-7.0-x86_64-Minimal.iso,xvdc:cdrom,r', 'phy:/dev/maxvm/tackc7,xvda,w' ]
#disk=[ 'phy:/dev/maxvm/tackc7,xvda,w' ]

#vfb=[ "type=vnc,vncunused=1,keymap=en-us" ]

extra=" rd_NO_LUKS rd.lvm=0 rd_NO_MD rd_NO_DM nodmraid net.ifnames=0 biosdevname=0 ipv6.disable=1 ks= text console=hvc0"

#extra = " root=/dev/xvda1 console=hvc0 "

on_reboot   = 'restart'

---------------- snip cfg -----------
Now your C6 e2fsprogs tools will work on the C7 device!
]$sudo kpartx -a -v  /dev/maxvm/tackc7       
add map maxvm-tackc7p1 (253:58): 0 8386560 linear /dev/maxvm/tackc7 2048

// now the 64bit flag is gone from `features`
]$ sudo dumpe2fs -h /dev/mapper/maxvm-tackc7p1
dumpe2fs 1.41.12 (17-May-2010)                                      
Filesystem volume name:   <none>                                    
Last mounted on:          /                                         
Filesystem UUID:          9d55016f-7604-4271-92bd-09c7ecbc1ae7      
Filesystem magic number:  0xEF53                                    
Filesystem revision #:    1 (dynamic)                               
Filesystem features:      has_journal ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize                                                                                  
Filesystem flags:         signed_directory_hash                                                                         
Default mount options:    user_xattr acl                                                                                
Filesystem state:         clean                                                                                         
Errors behavior:          Continue                                                                                      
Filesystem OS type:       Linux                                                                                         
Inode count:              262144                                                                                        
Block count:              1048320                                                                                       
Reserved block count:     52416                                                                                         
Free blocks:              801713                                                                                        
Free inodes:              237716                                                                                        
First block:              0                                                                                             
Block size:               4096                                                                                          
Fragment size:            4096                                                                                          
Reserved GDT blocks:      255                                                                                           
Blocks per group:         32768                                                                                         
Fragments per group:      32768                                                                                         
Inodes per group:         8192                                                                                          
Inode blocks per group:   512                                                                                           
Flex block group size:    16                                                                                            
Filesystem created:       Thu Feb 12 20:50:17 2015                                                                      
Last mount time:          Thu Feb 12 21:03:17 2015                                                                      
Last write time:          Thu Feb 12 21:03:16 2015                                                                      
Mount count:              2                                                                                             
Maximum mount count:      -1                                                                                            
Last checked:             Thu Feb 12 20:50:17 2015                                                                      
Check interval:           0 (<none>)                                                                                    
Lifetime writes:          1443 MB                                                                                       
Reserved blocks uid:      0 (user root)                                                                                 
Reserved blocks gid:      0 (group root)                                                                                
First inode:              11                                                                                            
Inode size:               256                                                                                           
Required extra isize:     28                                                                                            
Desired extra isize:      28                                                                                            
Journal inode:            8                                                                                             
Default directory hash:   half_md4                                                                                      
Directory Hash Seed:      313f65e5-f4ad-4096-8219-65a00631729d                                                          
Journal backup:           inode blocks                                                                                  
Journal features:         journal_incompat_revoke                                                                       
Journal size:             64M                                                                                           
Journal length:           16384                                                                                         
Journal sequence:         0x000007e6                                                                                    
Journal start:            0                                                                                             

]$ sudo e2fsck /dev/mapper/maxvm-tackc7p1
e2fsck 1.41.12 (17-May-2010)                                   
/dev/mapper/maxvm-tackc7p1: clean, 24428/262144 files, 246607/1048320 blocks

]$ sudo kpartx -d -v  /dev/maxvm/tackc7
del devmap : maxvm-tackc7p1

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