Let say that my installation of 1708 went well and then the update to 1810 went well also.
I'm stuck on several issues:
When I 'cat /etc/fstab" I see "UUID=099d7278-4cb9-434a-b933-c684434d6365 /boot ext defaults 1 2"
But when I enter 'df -h' I see " /dev/md126 2.0G 270M 1.6G 15% /boot"
When I comment out the UUID line and add the /dev/md126 I get an error - sometimes (requires a boot to rescue go back to the UUID).
When I installed CentOS 6 it allowed me to control the name of the MD devices for both /boot and the LVM raid devices. Why not with CentOS 7?
Why is it when I install CentOS 7 over an existing CentOS 6 file systems (I want to keep the allocations the same) CentOS 7 really doesn't like it??? I found myself deleting and reallocating the same partitions. Especially the /boot raid-1 allocations - it always comes up as 'unknown' .
I guess I'm old school because I like the flow of CentOS 6 as-far-as disks are concerned (i..e. allocate raid device from first disk; allocate raid device from second disk; create raid partition by adding the 2 raid devices; label it as /dev/md0 with a mount point of /boot; etc). CentOS 7 just seems odd they way it's done.
Can someone help me understand what I'm doing?
TIA
Gene
Need Help Understanding
Need Help Understanding
Happily Retired
Gene Poole
Woodstock, Georgia
Gene Poole
Woodstock, Georgia
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- Posts: 2019
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Re: Need Help Understanding
I don't see any issues with UUID .
Most probably , in initramfs there are some naming issues with MD devices (most probably your MD Is named different) and later when the switch root comes - everything goes to it's place.
Out can try to create an /etc/mdadm.conf and run dracut to rebuild your initramfs.
Once done, check the content of the initramfs to verify the config is inside. Then, give it a try
Most probably , in initramfs there are some naming issues with MD devices (most probably your MD Is named different) and later when the switch root comes - everything goes to it's place.
Out can try to create an /etc/mdadm.conf and run dracut to rebuild your initramfs.
Once done, check the content of the initramfs to verify the config is inside. Then, give it a try
Re: Need Help Understanding
I'm guessing that the 'unknown' issue is due to the difference in the metadata for /boot raid-1 device. That just tells me that there are some 'backwards compatibility' issues.
After install and I enter 'cat /proc/mdstat' the names of the MD devices are /dev/md124, /dev/md125, etc which under CentOS 6 aren't allowed (I can only name them /dev/md0 through /dev/md15 - which seems logical to me - BTW, IBM started the naming of things from 0). So, Why can't I name the MD devices as in CentOS 6? Why take a (under CentOS 6) default name? Should I forget everything (in this area) I learned in the past? Was the kernel jump from 2.6 to 3.10 so big that they eliminated so much?
I googled looking for a CentOS 7 Installation Guide with no luck so I started checking out the RHEL 7 installation guide but they didn;t spend much time on Software RAID. Has any one seen a good guide or tutorial on this? Where I'm lost is on the screem where you define the mount points and stuff, is 2 fields ('label' and 'name') I 'm looking for a explanation on how to use them. OK, I guessed and started using the 'name' field for the LV name (i.e. /home would be lv_home because I use LVM). But, shouldn't that mean I could use the 'label' field to put, for example, /dev/md0 for the /boot raid-1, etc? If this is important, should I just define everything singular and after the install is complete using sfdisk and mdadm to create the RAID devices manually?
Just don't understand.
Gene
After install and I enter 'cat /proc/mdstat' the names of the MD devices are /dev/md124, /dev/md125, etc which under CentOS 6 aren't allowed (I can only name them /dev/md0 through /dev/md15 - which seems logical to me - BTW, IBM started the naming of things from 0). So, Why can't I name the MD devices as in CentOS 6? Why take a (under CentOS 6) default name? Should I forget everything (in this area) I learned in the past? Was the kernel jump from 2.6 to 3.10 so big that they eliminated so much?
I googled looking for a CentOS 7 Installation Guide with no luck so I started checking out the RHEL 7 installation guide but they didn;t spend much time on Software RAID. Has any one seen a good guide or tutorial on this? Where I'm lost is on the screem where you define the mount points and stuff, is 2 fields ('label' and 'name') I 'm looking for a explanation on how to use them. OK, I guessed and started using the 'name' field for the LV name (i.e. /home would be lv_home because I use LVM). But, shouldn't that mean I could use the 'label' field to put, for example, /dev/md0 for the /boot raid-1, etc? If this is important, should I just define everything singular and after the install is complete using sfdisk and mdadm to create the RAID devices manually?
Just don't understand.
Gene
Happily Retired
Gene Poole
Woodstock, Georgia
Gene Poole
Woodstock, Georgia
Re: Need Help Understanding
What's the matter with using UUIDs? They are unique and are the preferred method to mount things.
The future appears to be RHEL or Debian. I think I'm going Debian.
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Info for USB installs on http://wiki.centos.org/HowTos/InstallFromUSBkey
CentOS 5 and 6 are deadest, do not use them.
Use the FAQ Luke
Re: Need Help Understanding
I've no problem using the UUID as that's the way CentOS 7 is running now - but just for the /boot raid-1 device. I just like things consistent. If something goes wrong with the hard drive(s) that the /boot raid device is on, by looking at /dev/md0 with cat /proc/mdstat I know exactly what disk drive is causing me issues. It become more difficult when you have several raid-1 devices.
On CentOS 6 the /boot raid-1 device would always be /dev/md0.
It just seems things have been made different when it wasn't necessary.
Gene
On CentOS 6 the /boot raid-1 device would always be /dev/md0.
It just seems things have been made different when it wasn't necessary.
Gene
Happily Retired
Gene Poole
Woodstock, Georgia
Gene Poole
Woodstock, Georgia
Re: Need Help Understanding
OK, So far I think I've solved all of my hard drive issues!
What I did was to reinstall CentOS 6 because I can define everything just like I want it to be.
The hard drive environment is:
2 - 120 GB WD SATA Drives
4 - 4 TB WD SATA Drives
On the 120 GB drives I've defined the following RAID-1 devices:
/dev/md0 - /dev/sda1 | /dev/sdb1 - /boot - 2 GB
/dev/md1 - /dev/sda2 | /dev/sdb2 - /dev/vg_osswap/ 32 GB - lv_sysswap 16 GB - swap
/dev/md2 - /dev/sda3 | /dev/sdb3 - /dev/vg_opsys/ 78 GB - lv_root 8 GB - /name I entered lv_sysswap
- lv_archive 2 GB - /archive
- lv_home 4 GB - /home
- lv_opt 2 GB - /opt
- lv_tmp 5 GB - /tmp
- lv_usr - 12 GB - /usr
- lv_usr_local 2 GB - /usr/local
- lv_var 8 GB - /var
On the 4 - 4 TB dribes I've defined the following RAID-10 device:
/dev/md3 - /dev/sd(c-f)1 - /dev/vg_sysdata 7.28 TB - Many lv_ devices.
The definitions for /dev/md0; /dev/md1; /dev/md2 are built from a custom kickstart DVD that was built from RHEL 4 and constantly modified since then so it works with CentOS 6. However, I do not have custion install DVD for CentOS 7 so I have to do the install manually.
When I did the CentOS 7 1708 install and I got to the 'Custom Partition' page I did the following:
The allocation for /boot shows up as 'unknown' so I entered the mount point as /boot; I selected reformat as ext4; it did show up as raid 1; in the label I entered /dev/md0; in the name I entered boot.
The allocation for swap shows up as CentOS 6.10 so there was no mount point; reformated as swap; in the label I entered /dev/md1; in the name I entered lv_sysswap.
For all of the other defined OS file systems I added the mount points; reformatted as ext4; they showed up as raid-1 but in the label I entered /dev/md2 for all of them; in the name I entered the lv name as shown above.
What was strange was that when I did the raid-10 file systems there was information in the label and name fields already.
So going forward I will continue to use the 1708 DVD after I verify that all of the allocations are basically the same across board.
I think I understand as much as I need to at this point.
Gene
What I did was to reinstall CentOS 6 because I can define everything just like I want it to be.
The hard drive environment is:
2 - 120 GB WD SATA Drives
4 - 4 TB WD SATA Drives
On the 120 GB drives I've defined the following RAID-1 devices:
/dev/md0 - /dev/sda1 | /dev/sdb1 - /boot - 2 GB
/dev/md1 - /dev/sda2 | /dev/sdb2 - /dev/vg_osswap/ 32 GB - lv_sysswap 16 GB - swap
/dev/md2 - /dev/sda3 | /dev/sdb3 - /dev/vg_opsys/ 78 GB - lv_root 8 GB - /name I entered lv_sysswap
- lv_archive 2 GB - /archive
- lv_home 4 GB - /home
- lv_opt 2 GB - /opt
- lv_tmp 5 GB - /tmp
- lv_usr - 12 GB - /usr
- lv_usr_local 2 GB - /usr/local
- lv_var 8 GB - /var
On the 4 - 4 TB dribes I've defined the following RAID-10 device:
/dev/md3 - /dev/sd(c-f)1 - /dev/vg_sysdata 7.28 TB - Many lv_ devices.
The definitions for /dev/md0; /dev/md1; /dev/md2 are built from a custom kickstart DVD that was built from RHEL 4 and constantly modified since then so it works with CentOS 6. However, I do not have custion install DVD for CentOS 7 so I have to do the install manually.
When I did the CentOS 7 1708 install and I got to the 'Custom Partition' page I did the following:
The allocation for /boot shows up as 'unknown' so I entered the mount point as /boot; I selected reformat as ext4; it did show up as raid 1; in the label I entered /dev/md0; in the name I entered boot.
The allocation for swap shows up as CentOS 6.10 so there was no mount point; reformated as swap; in the label I entered /dev/md1; in the name I entered lv_sysswap.
For all of the other defined OS file systems I added the mount points; reformatted as ext4; they showed up as raid-1 but in the label I entered /dev/md2 for all of them; in the name I entered the lv name as shown above.
What was strange was that when I did the raid-10 file systems there was information in the label and name fields already.
So going forward I will continue to use the 1708 DVD after I verify that all of the allocations are basically the same across board.
I think I understand as much as I need to at this point.
Gene
Happily Retired
Gene Poole
Woodstock, Georgia
Gene Poole
Woodstock, Georgia
Re: Need Help Understanding
How do I mark this post as solved?
Happily Retired
Gene Poole
Woodstock, Georgia
Gene Poole
Woodstock, Georgia