Category: linux

Split Mirror in RHEL

Posted on by Bian Xi Leave a Comment on Split Mirror in RHEL

Split Mirror in RHEL

To copy one LV to another VG using LV mirror method. This method can not be performed on-line because of vgsplit command.

Note: RHEL doesn't have cplv command.

Steps

vgcreate vg01 /dev/vdb
lvcreate -L 1G -n test1 vg01
vgextend vg01 /dev/vdc
lvconvert --type raid1 --mirrors 1 /dev/vg01/test1 /dev/vdc
lvdisplay -m vg01/test1
lvconvert --splitmirrors 1 --name test2 /dev/vg01/test1
lvdisplay -m vg01/test1
lvdisplay -m vg01/test2
vgchange -a n vg01
vgsplit -t -v /dev/vg01 /dev/vg02 /dev/vdc
vgsplit -v /dev/vg01 /dev/vg02 /dev/vdc
lvs
vgchange -a y vg01
vgchange -a y vg02

References

How to move / copy logical volume (lv) to another volume group (vg)?

Unable to query DNS with DOMAIN from `dnsmasq` server

Posted on by Bian Xi Leave a Comment on Unable to query DNS with DOMAIN from `dnsmasq` server

Unable to query DNS with DOMAIN from dnsmasq server

When doing nslookup, dnsmasq server could not reply the DNS with DOMAIN, but able to reply short dns name only. Following message may appear.

# nslookup www
....
dnsmasq server can't find www.example.com: NXDOMAIN

Solution

The reason is that DNS entries in dnsmasq host file (default is banner_add_hosts) has no domain name

192.168.1.1  www

In dnsmasq.conf file

Following lines are required. The expand-hosts option allows appending the domain name defined in domain line to short hostname in host file

domain=example.com,192.168.1.0/24
expand-hosts

References

Escape Percent-signs(%) in crontab

Posted on by Bian Xi Leave a Comment on Escape Percent-signs(%) in crontab

Escape Percent-signs (%) in crontab

In order to input % character as command parameter in cron task, it needs to be escaped using backslash ().

man (5) crontab:

Percent-signs (%) in the command, unless escaped with backslash (\), 
will be changed into newline characters, and all data after the 
first % will be sent to the command as standard input.

Exclude files when run `rmlint`

Posted on by Bian Xi Leave a Comment on Exclude files when run `rmlint`

Exclude files when run rmlint

To exclude files, using find command, then pass the parameter - to rmlint as folder name

$ find /target/dir -type f ! -name '*.nib' ! -name '*.icon' ! -name '*.plist' | rmlint [options] -

For only search specific type of file, can use following command:

find /mm -iname "*.DFF" -type f | rmlint -T df --config=sh:handler=hardlink -

References

How do I exclude/ignore specific file types/extensions with rmlint?

Convert Oracle Linux 7.9 to Proxmox

Posted on by Bian Xi Leave a Comment on Convert Oracle Linux 7.9 to Proxmox

Convert Oracle Linux 7.9 to Proxmox

This is to describe how to convert Oracle Linux 7.9 to Proxmox.

VM creation

Following hardware options can be considered

  • BIOS: SeaBIOS (Should be able to see Grub menu)
  • Machine: Default (i440fx)
  • SCSI Controller: VirtIO SCSI (It might not be used as sata0 to be considered for disk)
  • Hard Disk (sata0): disk_image_file
  • Network Device (net0): vmxnet3=<mac_address> (This is default for VMware, can use other type too)

Convert the VMware disk to Proxmox disk and attach the disk to new VM

qm importdisk 121 oracle18c.vmdk pool240ssd --format qcow2

Attach the disk as sata0.

Boot

Select item Oracle Linux Server (0-rescue-ed95572bd80641d79f83cd91e03c0283 with Linux) 7.9 from Grub menu to boot into rescue mode.

Note: Tried other option, all got error and unable to boot

Kernel

Find Kernel Package

Login as valid user, then find out the kernel to be used

rpm -q -a | grep kernel | sort

Got following list

kernel-3.10.0-1160.25.1.el7.x86_64
kernel-3.10.0-1160.36.2.el7.x86_64
kernel-3.10.0-1160.el7.x86_64
kernel-tools-3.10.0-1160.36.2.el7.x86_64
kernel-tools-libs-3.10.0-1160.36.2.el7.x86_64
kernel-uek-5.4.17-2102.203.6.el7uek.x86_64
kernel-uek-5.4.17-2102.204.4.2.el7uek.x86_64
kernel-uek-5.4.17-2102.204.4.4.el7uek.x86_64

Choose the latest one, which is also Unbreakable Enterprise Kernel

Recreate Grub kernel files

Find scripts in Kernel package

rpm -q kernel-uek-5.4.17-2102.204.4.4.el7uek.x86_64 --scripts

Following posttrans scriptlet shown

...
posttrans scriptlet (using /bin/sh):
/usr/sbin/new-kernel-pkg --package kernel --mkinitrd --dracut --depmod --update 5.4.17-2102.204.4.4.el7uek.x86_64 || exit $?
/usr/sbin/new-kernel-pkg --package kernel --rpmposttrans 5.4.17-2102.204.4.4.el7uek.x86_64 || exit $?
...

Run above commands to rebuild Grub files, then reboot the system to the menu with kernel recreated.

Note: The error Unable to open file: /etc/keys/x509_ima.der (-2) can be ignored

Network

You can reconfigure network interface the same as VMware, this is to avoid reconfiguration of network settings

Interface Type

Check VMWare vmx file to find disk type, then set the same in Proxmox

ethernet0.virtualDev = "vmxnet3"

Mac Address

You can change Mac Address using the value in VMWare configuration

ethernet0.generatedAddress = "00:11c:22:33:44:55"

Interface Name

Find out the interface in /etc/sysconfig/network-scripts as below.

/etc/sysconfig/network-scripts/ifcfg-ens192

The interface name is ifcfg-ens192

Create the file /etc/udev/rules.d/70-custom-ifnames.rules with the following contents:

SUBSYSTEM=="net",ACTION=="add",ATTR{address}=="00:11:22:33:44:55",ATTR{type}=="1",NAME="ens192"

Then reboot the server, then check the Interface and IP address using ip a command.

References

Consistent network interface device naming