Estrategias de reversión

# Install Timeshift
sudo apt install timeshift -y
 
# Create a snapshot
sudo timeshift --create --comments "Pre-upgrade backup" --tags D
 
# List snapshots
sudo timeshift --list

# List available snapshots
sudo timeshift --list
 
# Restore a specific snapshot
sudo timeshift --restore --snapshot "2026-03-24_10-00-00"
 
# You will be prompted to confirm; choose what to restore
# Reboot after restoration is complete
sudo reboot

# In the live environment
sudo apt update
sudo apt install timeshift -y
 
# Timeshift will automatically detect snapshots on disk
sudo timeshift --list
 
# Restore a snapshot
sudo timeshift --restore --snapshot "2026-03-24_10-00-00"
sudo reboot

# View existing logical volumes
sudo lvs
sudo vgs  # Confirm the volume group has enough free space
 
# Create a snapshot for the root partition (requires free space in the volume group)
sudo lvcreate -L 10G -s -n root-snap /dev/ubuntu-vg/ubuntu-lv
 
# If there is a separate /var partition
sudo lvcreate -L 5G -s -n var-snap /dev/ubuntu-vg/var-lv
 
# Verify the snapshot
sudo lvs

# Method 1: Merge the snapshot (requires unmounting or operating from Live USB)
 
# If you can still access the system
# Mark the snapshot for merge (takes effect on next activation)
sudo lvconvert --merge /dev/ubuntu-vg/root-snap
 
# The merge will execute automatically after reboot
sudo reboot
 
# Method 2: Operate from Live USB
# Boot from Live USB
sudo apt install lvm2 -y
sudo vgchange -ay  # Activate volume groups
 
# Execute the merge
sudo lvconvert --merge /dev/ubuntu-vg/root-snap
sudo reboot

# View current LVM usage
sudo vgs
 
# If VFree is 0, you can shrink an existing logical volume (dangerous, proceed with caution)
# Shrink the filesystem first, then shrink the logical volume
# Recommended to do this from a Live USB
 
# Check the filesystem
sudo e2fsck -f /dev/ubuntu-vg/ubuntu-lv
 
# Shrink the filesystem to 15G
sudo resize2fs /dev/ubuntu-vg/ubuntu-lv 15G
 
# Shrink the logical volume to 16G (leave some headroom)
sudo lvreduce -L 16G /dev/ubuntu-vg/ubuntu-lv
 
# Now there is space to create a snapshot
sudo lvcreate -L 10G -s -n root-snap /dev/ubuntu-vg/ubuntu-lv

# View Btrfs subvolumes
sudo btrfs subvolume list /
 
# Create a read-only snapshot
sudo btrfs subvolume snapshot -r / /snapshots/pre-upgrade-$(date +%Y%m%d)
 
# List snapshots
sudo btrfs subvolume list / | grep snapshot

# Boot from Live USB
# Mount the Btrfs partition
sudo mount /dev/sda2 /mnt
 
# View subvolumes
sudo btrfs subvolume list /mnt
 
# Rename the current root subvolume
sudo mv /mnt/@ /mnt/@broken
 
# Create a new root subvolume from the snapshot
sudo btrfs subvolume snapshot /mnt/snapshots/pre-upgrade-20260324 /mnt/@
 
# Reboot
sudo reboot

# Recommended to create from Live USB to ensure partitions are unmounted
# Full disk image
sudo dd if=/dev/sda of=/mnt/external/full-disk.img bs=4M status=progress
 
# Compressed image
sudo dd if=/dev/sda bs=4M status=progress | gzip > /mnt/external/full-disk.img.gz
 
# Back up a specific partition only
sudo dd if=/dev/sda2 of=/mnt/external/root-partition.img bs=4M status=progress

# Boot from Live USB
# Restore the full disk
sudo dd if=/mnt/external/full-disk.img of=/dev/sda bs=4M status=progress
 
# Restore a compressed image
gunzip -c /mnt/external/full-disk.img.gz | sudo dd of=/dev/sda bs=4M status=progress
 
# Restore a single partition
sudo dd if=/mnt/external/root-partition.img of=/dev/sda2 bs=4M status=progress
 
# Update GRUB after restoration
sudo mount /dev/sda2 /mnt
sudo mount /dev/sda1 /mnt/boot/efi
sudo mount --bind /dev /mnt/dev
sudo mount --bind /proc /mnt/proc
sudo mount --bind /sys /mnt/sys
sudo chroot /mnt
grub-install /dev/sda
update-grub
exit
sudo reboot

# Alibaba Cloud - create a snapshot using CLI
aliyun ecs CreateSnapshot --DiskId d-xxx --SnapshotName pre-upgrade
 
# Tencent Cloud
tccli cbs CreateSnapshot --cli-input-json '{"DiskId":"disk-xxx","SnapshotName":"pre-upgrade"}'
 
# AWS
aws ec2 create-snapshot --volume-id vol-xxx --description "pre-upgrade"
 
# To restore: use "Roll Back Disk" or "Create Disk from Snapshot" in each platform's console

# Configure unconfigured packages
sudo dpkg --configure -a
 
# Fix dependencies
sudo apt --fix-broken install
 
# Reinstall a problematic package
sudo apt install --reinstall package-name
 
# Force reinstall
sudo dpkg -i --force-overwrite /var/cache/apt/archives/package-name*.deb

# Select "Advanced options for Ubuntu" from the GRUB menu
# Choose an older kernel version to boot
 
# If the GRUB menu doesn't appear (countdown too short)
# Hold Shift during boot (BIOS) or press Esc (UEFI)
 
# After entering the system, fix kernel issues
sudo apt install --reinstall linux-image-$(uname -r)
sudo update-grub

# Select Recovery Mode from GRUB
# Available options:
# - dpkg    fix broken packages
# - fsck    check filesystem
# - network enable networking
# - root    enter root shell
 
# In the root shell
mount -o remount,rw /
apt --fix-broken install
dpkg --configure -a
reboot

Issue found after upgrade
  |-- Is the issue fixable?
  |   |-- Yes -> Fix the specific issue (package repair, config adjustment)
  |   +-- No -> Continue assessment
  |
  |-- Is there a system snapshot?
  |   |-- Yes -> Restore snapshot (Timeshift/LVM/Btrfs)
  |   +-- No -> Continue assessment
  |
  |-- Is there a disk image?
  |   |-- Yes -> dd restore
  |   +-- No -> Continue assessment
  |
  +-- Last resort
      +-- Reinstall system + restore data and configs from backup