Linux bash backup script - 12, 9, 6, 3, 1 months - linux

Question

I am writing a bash backup script, and it's working excellent so far. The problem is that it clutters up my harddrive in no time.
The backup runs weekly on sundays.
I would like to:
Save the most recent 4 backups
Save the backup which is 3 months old
Save the backup which is 6 months old
Save the backup which is 12
months old
Now how do i achieve this?
I think i can work out how to "check if file exists", but i'm having trouble getting my head around how to delete the correct backups.
The backup 3 months old, will be 3 months and 1 week old by next week - and thus be deleted..
Is there any geniously simple way to work around this that i may have overlooked..?
Thanks in advance,

Answer 1

If you give your Backup files a nice naming scheme like: 10.29.15-BACKUP.zip you could always do it real easily. Easiest where you can just have 2 separate folders one for Daily Backups and one for Archives.
So in your bash script:
#BACKUP PROCESS HAPPENS HERE, PLACES BACKUP NAMED 10.29.15-BACKUP.zip in /home/User/DailyBackups FOLDER, WHICH WE WILL CALL $CurrentBackup
#Get Date from 3 months ago
ChkDate=`date --date="-3 months" +%m.%d.%y`
#See if this file exists
ls $ChkDate-BACKUP.zip /home/User/BackupArchive/
#If it does exist then copy current backup to BackupArchive Folder and Remove any backups older than 367 days from the BackupArchive Folder
if [[ $? == 0 ]]; then
cp /home/User/DailyBackups/$CurrentBackup /home/User/BackupArchive/$CurrentBackup
find /home/User/BackupArchive/*-BACKUP.zip -mtime +367 -exec rm {} \
fi
#Remove all but the most recent 4 Backups
for i in `ls -t /home/User/DailyBackups/*-BACKUP.zip | tail -n +5`; do
rm "$i"
done
I used 367 to account for a 366 day leap year and just in case your one year backup was a bit off, like 366 days and 1 minute.

Answer 2

I had a similar task to delete files up to n date what i had to do was:
1. generate an interval date from todays date (like 3 months ago)
[this post has a good writeup about getting specific dates
http://stackoverflow.com/questions/11144408/convert-string-to-date-in-bash]
2. loop over all the files in the location and get their time\date stamp with
date -r <filename> +%Y
date -r <filename> +%m
date -r <filename> +%d
3. Compare file date to interval date from todays date and keep if it matches or delete if not.
Hope this helps you to get the concept going

Answer 3

Suppose you named the backup according to the date:
% date +%Y-%m-%d
2015-10-29
Then you can compute the date one year ago like this:
% date +%Y-%m-%d -d "-1 year"
2014-10-29
and the date 5 weeks ago like this:
% date +%Y-%m-%d -d "-5 weeks"
2015-09-24
So you can setup cronjobs with run every 3 months and every Sunday,
and delete backups that occurred one year ago and 5 weeks ago like this:
# Every 3 months, run the backup script
1 2 * */3 * /path/to/backup/script.sh > /path/to/backupdir/$(date +%Y-%m-%d-Q)
# Every 3 months, delete the backup made on that date the previous year
1 2 * */3 * /bin/rm /path/to/backupdir/$(date +%Y-%m-%d-Q -d "-1 year")
# Every Sunday, if backup does not exist, run backup script
1 3 * * 7 if [ ! -f /path/to/backupdir/$(date +%Y-%m-%d-Q) ]; then /path/to/backup/script.sh > /path/to/backupdir/$(date +%Y-%m-%d) fi
# Every Sunday, delete backup 5 weeks old
1 3 * * 7 /bin/rm /path/to/backupdir/$(date +%Y-%m-%d -d "-5 weeks")
Note that
We want to be careful not to run the backup script twice on the same day, for
example, when a quarterly backup happens on a Sunday. If the quarterly backup
cronjob is set to run (at 2:00AM), before the weekly backups (at 3:00AM), then
we can prevent the weekly backup from running by testing if the backup filename
already exists. This is the purpose of using
[ ! -f /path/to/backupdir/$(date +%Y-%m-%d-Q) ]
When we delete backups which are 5 weeks old, we do not want to delete quarterly backups.
We can prevent that from happening by naming the quarterly backups a little differently than the weekly backups, such as with a Q:
% date +%Y-%m-%d-Q
2015-10-29-Q
so that the command to remove weekly backups,
/bin/rm /path/to/backupdir/$(date +%Y-%m-%d -d "-5 weeks")
will not remove quarterly backups.