![10
Introducing “Snapper” – CLI example
Snapper headers:
– Type : [ Pre | Post | Single ]
– # : Nr of snapshot
– Pre # : if type is “Post” the matching Pre nr.
– Date : timestamp
– Cleanup : cleanup algorithm for this snapshot
– Description : A fitting description of the snapshot (free
text)
– Userdata : key=value pairs to record all sorts of useful
information about the snapshot in an easily
parsable format](https://image.slidesharecdn.com/linuxconeurope2014fullsystemrollbackbtrfssnapper0-141022115724-conversion-gate01/85/Linux-con-europe_2014_full_system_rollback_btrfs_snapper_0-10-320.jpg)
Linux con europe_2014_full_system_rollback_btrfs_snapper_0
- 1. Full System Rollback using Btrfs and Snapper Matthias G. Eckermann Senior Product Manager mge@suse.com LinuxCon Europe 2014 2014-10-05 12:00 UTC
- 2. Why?
- 3. 3 RAS System Rollback High Availability Live Kernel Patching Increase Uptime
- 4. 4 RAS High Availability Live Kernel Patching Increase Uptime System Rollback
- 5. 5 System Rollback Reduce Operational Downtime Goal Go back to well-known system state Peace of mind for • System administrative tasks • Package and patch installation • System upgrades
- 8. 8 Demonstration #1 Using Snapshots with YaST2 snapper # Description Tools 1 Track and visualize YaST activities with snapper Start YaST2 Create a new user (yast users) Start YaST snapper View the changes 2 Undo some of the changes Start YaST snapper Select the snapshot pair created by the “yast users” module 3 Install a new package by either using YaST2 and visualize the result using YaST2 snapper YaST2
- 9. 9 Snapper Functionality • Manage snapshots ‒ Automatically create snapshots ‒ Display differences between snapshots ‒ Roll-back • Integration into system / systems management stack ‒ ZYpp, YUM, (apt?) ‒ LinuxPAM • User Interfaces ‒ CLI ‒ DBUS ‒ Graphical (YaST) ‒ GUI integration (in development / GSoC)
- 10. 10 Introducing “Snapper” – CLI example Snapper headers: – Type : [ Pre | Post | Single ] – # : Nr of snapshot – Pre # : if type is “Post” the matching Pre nr. – Date : timestamp – Cleanup : cleanup algorithm for this snapshot – Description : A fitting description of the snapshot (free text) – Userdata : key=value pairs to record all sorts of useful information about the snapshot in an easily parsable format
- 11. 11 Demonstration#3 Snapper Command Line # Description Tools 1 List the currently available snapshots “snapper list ...” 2 Show differensce in the snapshot pair created by “yast users” “snapper status ...” 3 Show the difference only in /etc/shadow in the snapshot pair created by “yast users” “snapper diff ...” 4 Undo a change remove unnecessary files in the user's home dir; then execute “snapper undochange ...” 5 Create your own snapshot and modify its description “snapper create … -d <description>” “snapper modify … <num>” 6 Add key-value pair to existing snapshot “snapper modify … --userdata … <num>” 7 Create your own snapshot pair “snapper create –print-number --type pre ...” “snapper create --type post --pre-number <n1>...” 8 Change description and user data “snapper modify … <num>” 9 Rollback the full system “snapper rollback … <num> | current”
- 12. 12 Special Use case: Snapper and ITIL # @Begin of implementation Change: snapper create --type pre --description "ChgMgt Work order: Upgrade syslog configuration to forward log entries to central log server" --userdata "WorkOrder=201201253030000012-1, State=InProgress,Agent=jdoe@example.com" # @End of implementation Change: snapper create --type post --pre-number 240 --description "Done: ChgMgt Work order: Upgrade syslog configuration to forward log entries to central log server" --userdata "WorkOrder=201201253030000012-1, State=Closed, Agent=jdoe@example.com"
- 13. Rollback
- 14. 14 File based Rollback How it works • The system uses the same instance of a subvolume: “working instance” • single files are copied from the snapshot to the “working instance” – using CoW Benefits • Subvolumes are treated as read-only • Subvolumes can be used for Backup • Supports Pick and Choose Disadvantages • rollback not “atomic” → Implemented in Snapper as “undochange”
- 15. 15 Rollback per Subvolume How it works • Instead of the original subvolume, the snapshot is mounted with the options “subvol=<name>” ‒ Remember: snapshots are subvolumes • “btrfs subvolume set-default ...” for permanent assignments Benefits • “atomic” operation • Very fast Disadvantages • Additional complexity ‒ Require explicit mounting of subvolumes • No “rollback” per single file → “Full System Rollback” → Implemented in Snapper as “rollback”
- 16. 16 Snapshot/Rollback – Overview Past & Present Present & Future • “snapper undochange” • Selective Rollback for ‒ Package updates ‒ Administrative changes • No rollback of ‒ Kernel / initrd ‒ Bootloader ‒ System data, e.g. /var/log • “snapper rollback” • Full Rollback for ‒ Package updates ‒ Administrative changes ‒ Kernel / initrd (initramfs) • No rollback of ‒ Bootloader ‒ Customer data: “/home”, if on own partition (default) ‒ System data, e.g. /var/log High Demand
- 17. 17 Snapshotting “/” – Challenges • Kernel and initrd / initramfs = “/boot” ‒ Grub2 booting from a snapshot = subvolume ‒ Mark snapshots with /boot relevance as such • System integrity and Compliance ‒ Don't allow to roll back certain log-files etc. ‒ Solution: subvolumes instead of directories for /tmp /opt /srv /var/spool /var/log /var/run /var/tmp ...
- 18. 18 Btrfs integration with ... • Installer ‒ Btrfs as root fs ‒ Recommendation for subvolume layout ‒ Check size of root partition ‒ Automated snapper configuration • Partitioner ‒ Create Btrfs ‒ Create subvolumes • Bootloader ‒ Find existing subvolumes (snapshots) ‒ Read existing subvolumes and boot from
- 20. 20 Full System Rollback – Use Cases • “I have changed something, the system is still working, but now some functionality is missing / performance is bad / ...” → reset the system, reboot, enjoy! → “Reboot later mode” • “Something changed, and the system is not booting anymore” (worst case scenario) → need immediate reboot → “Reboot now mode”
- 21. 21 Snapshot / Rollback Reboot Later Mode • Administrator is in a current read-write filesystem, but wants to rollback • “snapper list” to view and select a snapshot • Call “snapper rollback <number>” this will ● Create a new read-only snapshot of the currently running system ● Create a new read-write snapshot of the snapshot <number>, lineary after the just recently created read-only snapshot ● “setdefault” to the new read-write snapshot and reboot
- 22. 22 Snapshot / Rollback Reboot Now Mode • Boot into an existing read-only snapshot • The system should work, as all variable data are on writable subvolumes anyways. • To continue to work in this snapshot, the admin should call “snapper rollback” – this will ● Create a new read-only snapshot of the old read-write one, linearly after the last existing one ● Create a new read-write snapshot of the snapshot you are currently in in read-only mode, lineary after the just recently created read-only snapshot ● “setdefault” to the new read-write snapshot and reboot
- 23. User view on Snapshot History
- 24. 24 Snapshot / Rollback User view on Snapshot History (1) ro ro ro ro curr. rw
- 25. 25 Snapshot / Rollback User view on Snapshot History (2) ro ro ro ro curr. rw ro 1 ro-Clone
- 26. 26 Snapshot / Rollback User view on Snapshot History (3) btrfs subvol set-default 2 3 old rw ro ro ro ro new ro rw 1 ro-Clone rw-Clone = Rollback
- 27. 27 Snapshot / Rollback User view on Snapshot History (4) New Snapshots ro ro ro 3 new ro 4 rw old rw ro 5 4 Diffs are possible ro 6
- 28. 28 Snapshot / Rollback User view on Snapshot History (5) Condensed view What happens, if we rollback again? ro 3 ro 4 ro 5 ro 6 rw Caveat: this does not reflect 1:1 what happens technically.
- 29. 29 Demonstration#4 Full System Rollback # Description Tools 1 List the currently available snapshots “snapper list” 2 Install a new kernel “zypper in ...” 3 List the currently available snapshots “snapper list” 4 Show the current kernel version and reboot “uname -a ; reboot” 5 List the currently available snapshots “snapper list” 6 Rollback to the former version and reboot “snapper rollback <num> ; reboot” 7 List the currently available snapshots “snapper list” 8 Show the current kernel version “uname -a”
- 30. Summary
- 31. 31 “Snapper” availability ... http://software.opensuse.org/download/package?project=filesystems:snapper&package=snapper
- 32. 32 System Rollback Reduce Operational Downtime Goal Go back to well-known system state Peace of mind for • System administrative tasks • Package and patch installation • System upgrades
- 33. Thank you. 33 Go ahead, try btrfs and snapper today! Your questions!?
- 34. Appendix
- 35. Demo “scripts”
- 36. 36 Demonstration#2 btrfs subvols and snapshots # Description Tools 1 List the currently available subvolumes “btrfs subvol ...” 2 List the currently available subvolumes – display details about the “parents” of the subvolumes “btrfs subvol … -p ...” 3 Create your own subvolume “/mydata” “btrfs subvol ...”
- 37. 37 Demonstration#5 Migrating from ext3 to btrfs # Description Tools 1 Create a logical volume or partition or loop device. Name it “toconvert” or the like. 2 Create an ext3 filesystem on this “toconvert” and mount it to “/toconvert” “mkfs.ext3 -b 4096 ...” “mkdir”, “mount” 3 Create some directories and files on “/toconvert”. Optional: create md5 checksums “mkdir”, “vi” Optional: “md5sum” 4 Perform the conversion and mount the filesystem again “umount /toconvert” “btrfs-convert ... “mount ...” 5 Control, if your data are all there and check the optional md5sums “find”, “md5sum”, ... 6 Understand, how btrfs saves the old ext3 filesystem metadata. “/toconvert/ext2_saved/image” “mount -o loop ...”
- 38. 38 Demonstration#6 Using snapper for /home/$USER Requirements • /home/$USER is a btrfs subvolume • “snapper” with DBUS interface (SLES 11 SP3, openSUSE 12.3, ...) • Create a snapper configuration for the user allowing him/her to do snapshots Additional Option • Automated snapshotting on login/logout • Requires small changes to the configuration of Linux PAM (Pluggable Configuration Modules)
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