VirtualTam's bookmarks

1. What is the difference between /tmp and /var/tmp? 2022-02-02

   tags: linux, storage, tmp, unix

   [ permalink ]

   • https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard
   • /tmp - Directory for temporary files. Often not preserved between system reboots and may be severely size-restricted.
   • /var/tmp - Temporary files to be preserved between reboots.
2. Centos/RHEL 7 - Fix LVM boot issues after migration from ESXi to VirtualBox 2018-04-20

   tags: boot, bootloader/grub, filesystem, filesystem/lvm, fstab, linux, linux/centos, linux/kernel, linux/red-hat

   [ permalink ]

   Here are the steps I used to migrate a CentOS 7 VM from (presumably?) an ESXi server, to a local VirtualBox environment.

   The LVM volumes were not detected at boot, and after the boot timeout, the OS fell back to the Dracut emergency shell.

   • get a CentOS minimal installation CD
   • check the VM's resources and peripherals:
     • ensure there are no floppy drives (!)
     • setup CPU and RAM resources
     • check virtual drives
     • add an SCSI optical drive if needed
   • optional: convert the virtual drive images from VMDK to VDI
   • mount the CentOS installation disc
   • boot on the installation disc:
     • select "Troubleshooting", then "Rescue"
     • let the rescue utility detect filesystems and mountpoints
   • $ chroot to the detected environment
   • backup files:
     • /etc/fstab
     • /boot/grub/grub.cfg
   • under /boot, backup the initrd and initramfs for the current configuration (these will be overwritten)
   • compare the current /etc/fstab with the output of $ lsblk and $ blkid
   • if needed, manually edit /etc/fstab to use the appropriate block device UUIDs, identifiers and mountpoints
   • regenerate GRUB configuration:
     • $ grub2-mkconfig -o /boot/grub2/grub.cfg
   • if needed, reinstall GRUB:
     • $ grub-install /dev/sda
   • rebuild initrd:
     • $ mkinitrd --force /boot/<initrd_image> <kernel_version>
   • rebuild initramfs:
     • $ dracut --force <kernel_version>
   • exit the chroot
   • unmount the installation disc
   • reboot
   • optional but highly recommended: cross your fingers
   • ...
   • profit!
3. Windows - Locate & fix the MBR 2018-01-05

   tags: boot, microsoft/windows, partition, storage

   [ permalink ]

   • https://superuser.com/questions/510485/how-to-tell-which-physical-disks-have-bootable-mbr
   • https://neosmart.net/wiki/fix-mbr/
   • https://neosmart.net/wiki/reboot-and-select-proper-boot-device/
   • https://askubuntu.com/questions/859685/how-to-delete-the-bootable-flag-of-a-partition
   • https://superuser.com/questions/596919/how-to-set-boot-disk-flag-with-diskpart
4. Boxstarter - Repeatable, reboot resilient windows environment installations made easy using Chocolatey packages 2017-10-13

   tags: automation, microsoft/windows, package

   [ permalink ]
5. Ansible: Reboot a server and wait for it to come back 2017-01-16

   tags: asynchronous, configuration-management/ansible, host, linux, reboot

   [ permalink ]

   • https://docs.ansible.com/ansible/wait_for_module.html
   • https://stackoverflow.com/questions/30187705/it-is-possible-to-async-a-local-action-in-ansible
   • https://superuser.com/questions/1106349/cant-make-ansible-to-wait-for-a-server-to-reboot-and-continue-playbook-to-work