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126 lines
4.5 KiB
Markdown
126 lines
4.5 KiB
Markdown
Display a reminder when it's been more than N days since a backup
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=================================================================
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Backups are important, regular ones doubly so. Unfortunately it's very easy to forget to make regular backups. Since Qubes stores the date and time when a VM was backed up, we will use this information to remind the user (probably you) when it has been more than N days since a backup.
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Architecture
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------------
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We create a shell script that:
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- compiles the list of VMs which we care about ensuring regular backups for,
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- determines the oldest backup timestamp for those VMs,
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- checks how far that timestamp is in the past, and
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- if that timestamp is older than a threshold, pops up a notification in dom0.
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We use an "exclude file" to exclude some VMs which we don't backup, and therefore for which we should not check timestamps for.
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Since we're probably running on a laptop, we run the script daily using `anacron` instead of `cron`, since `anacron` will deal with situtions when the machine is frequently in "suspend" mode. (Which laptops are)
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We set up an anacrontab for our user (as opposed to using a system-wide one) and run `anacron` hourly using the user's `crontab`. This gives some minor security benefits (by not running things as root) and reduces the chance of accidentally causing problems in the system through misconfiguration.
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Implementation
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--------------
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#### Excludes file ####
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A plain text file containing the names of VMs which are not backed up. In this example, we save it in dom0, `/home/${USER}/backup/exclude_vms.txt`:
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```
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fedora-30
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whonix-gw-15
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whonix-ws-15
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```
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(you'll need to change as needed depending on your backup policy)
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#### Backup script ####
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Put this in dom0, probably in `/home/${USER}/backup/remind.sh`:
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```
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#!/bin/bash
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# Remind if this many days since backup
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DAYS_THRESHOLD=3
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# Setup variables
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BACKUP_DIR="/home/${USER}/backup"
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EXCLUDE_FILE=${BACKUP_DIR}/exclude_vms.txt
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# Build backup VM list
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ALL_VMS=(`/usr/bin/qvm-ls --raw-list`)
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EXCLUDE_VMS=(`/usr/bin/cat $EXCLUDE_FILE`)
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EXCLUDE_VMS+=("dom0")
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BACKUP_VMS=()
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for i in "${ALL_VMS[@]}"; do
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skip=
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for j in "${EXCLUDE_VMS[@]}"; do
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[[ $i == $j ]] && { skip=1; break; }
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done
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[[ -n $skip ]] || BACKUP_VMS+=("$i")
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done
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# Get oldest known backup TS
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TS=`/usr/bin/date +%s`
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echo "TS now: $TS"
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for vm in "${BACKUP_VMS[@]}"; do
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vm_ts=`/usr/bin/qvm-prefs --get $vm backup_timestamp`
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if [ "$vm_ts" -lt "$TS" ]; then
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echo "New oldest TS: $vm_ts"
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TS=$vm_ts
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fi
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done
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# Get delta between current time and oldest backup
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NOW=`/usr/bin/date +%s`
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DELTA=`/usr/bin/expr $NOW - $TS`
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DELTA_DAYS=`/usr/bin/expr $DELTA / 86400`
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echo "delta in seconds: $DELTA / days: $DELTA_DAYS"
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if [ "$DELTA_DAYS" -gt "$DAYS_THRESHOLD" ]; then
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/usr/bin/notify-send --expire-time 86400000 "It has been $DELTA_DAYS days since last backup"
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fi
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echo `/usr/bin/date` >> $BACKUP_DIR/reminders.log
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remind.sh (END)
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```
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Then mark it as executable with `chmod +x /home/${USER}/backup/remind.sh`.
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You can try running it right away to see how long it's been since your last backup.
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#### Anacrontab ####
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Anacron should be installed by default in dom0, but you can check it by running (in dom0): `dnf info cronie-anacron` and verifying the first line of the info is "Installed Packages".
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First some basic configuration:
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1. Make sure we have a .config directory: `mkdir -p ~/.config`
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1. Create an anacrontab file for your user: `touch ~/.config/anacrontab`
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1. Make sure we have a ~/.var/spool/anacron directory: `mkdir -p ~/.var/spool/anacron/`
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Now open up the file `${HOME}/.config/anacrontab` in your text editor of choice and add to it the following, replacing USERNAME_GOES_HERE with the dom0 user account name (to find it, `echo ${USER}`:
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```
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# /etc/anacrontab: configuration file for anacron
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# See anacron(8) and anacrontab(5) for details.
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SHELL=/bin/sh
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PATH=/sbin:/bin:/usr/sbin:/usr/bin
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MAILTO=USERNAME_GOES_HERE
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# the maximal random delay added to the base delay of the jobs
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RANDOM_DELAY=45
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# the jobs will be started during the following hours only
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START_HOURS_RANGE=3-22
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#period in days delay in minutes job-identifier command
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@daily 0 backup-reminder /home/USERNAME_GOES_HERE/backup/remind.sh
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```
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#### Crontab ####
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Finally, add the following to your crontab file, accessed by running `crontab -e`: (`crontab -e` is the only way you should access your crontab)
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```
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@hourly /usr/sbin/anacron -t ${HOME}/.config/anacrontab -S ${HOME}/.var/spool/anacron
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```
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