Linux Systems Security. Backup and Change Management NETS Fall 2016

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Joshua Chase
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1 Linux Systems Security Backup and Change Management NETS Fall 2016

2 Backup Security breaches can cast doubt on entire installations or render them corrupt Files or entire systems may have to be recovered from backup Many tools are available to help with this task in Linux Two of the more commonly used ones are rsync and duplicity

3 Legacy Tools cp is the original way to make a copy of a file, many limitations cpio, tar are archival tools created to copy files to backup media (tape by default) - satisfactory for years but they make it cumbersome to manage backup media Various software packages provide frontends to these tools in order to make backup/restore easier to manage and more robust

4 Rsync Rsync has a command line interface which resembles a smart cp, and provides a base for many backup software packages with GUIs Can preserve special files such as links and devices Can copy to or from local or remote destinations Provides standby device capability by synchronizing data stores

5 Rsync Can compress data in transit to save bandwidth It only sends changed data when source file is not compressed or encrypted, otherwise entire file is transmitted Can use ssh to encrypt remote backup transfers without requiring encryption of backup storage Lighter on bandwidth, heavier on cpu and memory Requires rsync be available at both ends of the connection if used over the network

6 Rsync Examples Simple local archive of user data rsync -ahv --delete ~/* /backup/username rsync -ahv --delete --exclude=~/mybackup ~/* ~/mybackup Local archive with history date=$(date "+%F-%H-%M") rsync -ahv --link-dest=/backup/current --delete --exclude={/proc/*,/tmp/ *,/run/*,/dev/*,/sys/*,/mnt/*,/lost+found,/media/*,/backup} /* /backup/ $date && ln -nsf /backup/$date /backup/current Remote archive with history date=$(date "+%F-%H-%M") rsync -ahv --link-dest=/backup/current --delete --exclude={/proc/*,/tmp/ *,/run/*,/dev/*,/sys/*,/mnt/*,/lost+found,/media/*,/backup} --rsh="ssh - l ssh-login-user" /* rsync-user@host:/backup/$date && ssh user@host ln -nsf /backup/$date /backup/current

7 Rsync Exercises Create a VM for a backup server with a minimum OS and add a drive with enough space to hold your ubuntu vm backup (probably about 6GB will do), put a filesystem on it and mount it on /backup Enable ssh root access to backup server vm either with password, or using keys from your ubuntu machine (modify sshd_config to allow root with password is easiest for the purpose of the lab exercise but not a good idea for production use) Run a remote rsync backup from your ubuntu machine to the backup server vm similar to the example from the slide Wait a while and rerun the backup to see how much additional data got transferred Examine the /backup filesystem on your backup server vm to see what it looks like (use df, ls -l)

8 Rsync Restore Restoration of user data can be done using rsync command to copy data from backup location Can be copied to user staging or live data location If you know you are only dealing with regular files, you can even just use cp since the backup filesystem is a synchronized duplicate of the original filesystem System recovery requires additional tasks to be performed to deal with the boot block Rsync the backup to a new drive Install the boot block using GRUB on the new drive Install the new drive and boot from it

9 Rsync Full System Restore On the backup server, build an ext4 filesystem on a new disk (e.g. fdisk /dev/sdb and create your partitions, then mkfs -t ext4 /dev/sdb1) and mount the new filesystem (e.g. mkdir /r ; mount /dev/sdb1 /r) rsync -a /wherever-your-backup-is /r Use blkid to get the uuid of the new disk and modify /r/etc/fstab to use the new uuid for the root filesystem Boot from the distribution media and select rescue mode Select the option to rescue a broken system and tell it to rebuild the grub boot loader, then reboot If you get dropped to a shell (probably will), do: mkdir /r mount /dev/sda1 /r mount --bind /proc /r/proc ; mount --bind /dev /r/dev ; mount --bind /sys /r/sys chroot /r grub-mkconfig > /boot/grub/grub.cfg Exit the chroot shell, unmount everything you mounted, and reboot

10 Duplicity Like rsync but does not require duplicity on the receiving backup host, stores metadata with backup Can use many different types of backend storage, including Amazon S3, although they require additional backend packages and configuration effort Encrypts tarballs as a storage mechanism, stores deltas in separate tarballs, may have more steps involved in recovery Written in python, heavier on bandwidth, lighter on cpu and memory, reimplements ssh in python duplicity /what/to/backup sftp://user@host/backup/directory

11 Other Backup Solutions Many GUI frontends to the rsync, duplicity, and tar cli tools Backintime, DejaDup, CronoPete, Timeshift, Duplicati Bacula, Amanda Mondo Rescue for disaster recovery

12 Change Management

13 Change Management Implementing and maintaining security is a continuous process, these activities cause changes to your systems It has been said that problems created when implementing changes cause approximately 3/4 of all outages ITIL (Information Technology Information Library) includes change management as part of its service management best practices, ISO also covers change management It involves setting up advisory boards and creating formal processes for implementing changes

14 ITIL Information Technology Information Library Created by the UK government in the 1980s A set of documents describing best practices for service management in the digital world Originally 30+ reference books, now 5 Most recently updated in 2011 Not the only way to manage change but has ties to ISO which makes it a good candidate for larger organizations concerned about standards for management

15 ITIL Vol. 3, Service Transition Volume 3 of ITIL includes change management Goals include minimal service disruption, back-out activity reduction, and economical resource usage to accomplish change 3 types of change might include rollout, normal change, and urgent/emergency change - organization dependent

16 Change Process Change requests can be used to document change purpose, justification, impacts, activities, risks, not all parts may be present at the start of the process Change advisory board evaluates requests and provides management approval/denial, including funding approval - may also be where activities and risks get defined Change activities include tasks to execute, but also describe testing and validation tasks

17 Testing and Validation Ideally changes are validated and tested before deployment in production Testing may be done in-house, or delegated Security patches are often considered tested when released by vendors Testing includes verifying the change achieved the stated goals without unexpected impacts - virtual machines are good ways to do testing and validation

Course 55187B Linux System Administration

Course 55187B Linux System Administration Course Outline Module 1: System Startup and Shutdown This module explains how to manage startup and shutdown processes in Linux. Understanding the Boot Sequence The Grand Unified Boot Loader GRUB Configuration