Posts Tagged ‘cron’

Schedule wireless availability using ddwrt

January 7, 2017 4 comments

Sometimes I have problems ending my internet use in time to get enough quality sleep.

So I decided to set up a schedule that automatically disables our wireless home network during certain night hours for “nights before work/school day” and slightly longer hours for “night before weekend day”. Luckily this is quite easily done with the ddwrt firmware that I run on my router.

I couldn’t use the “Radio Time Restrictions” feature under Wireless – Advanced Settings, because it only supports one uniform schedule for all days of the week. Instead I used ddwrt’s cron support and the wl command.

I configured the following entries under Administration – Management – Cron. This turns on the wireless every morning at 6am, shuts it down at 10:30pm on Sunday to Thursday and shuts it down at 11:45pm on Friday and Saturday:

00 06 * * *   root wl radio on
30 22 * * 0-4 root wl radio off
45 23 * * 5-6 root wl radio off
Categories: coding Tags: , , ,

Nightly file server backups to external harddrive

December 8, 2013 Leave a comment

I use a small headless Debian system as file server for all family photos, videos, documents, etc. Its hostname is “bubba”. I have recently set it up to run backups to an external harddrive, using cron and rsync.

The external disk is a 500G laptop SATA disk in an USB/eSATA enclosure. It requires no separate power supply. So far I have only got it to work over USB. Somehow the eSATA does not work for me on Debian 6 (aka “squeeze”), even though the file server has an eSATA port.


sudo mkdir /mnt/backup
sudo apt-get install ntfs-3g

NTFS mount/unmount with sudo

I use NTFS as the filesystem on the backup disk because we wanted it to be compatible with MS Windows. The Debian Linux on the file server uses ntfs-3g for mounting the disk read-write. Unfortunately that only works well with root rights, so I configured sudo to permit myself password-less mounting and unmounting of the device.

/etc/sudoers entry
oliver ALL = NOPASSWD: /bin/mount /mnt/backup, \
                       /bin/umount /mnt/backup

Nightly rsync

The nightly backup process itself is a simple non-destructive local rsync command, wrapped by mount and unmount commands, to make sure that we can unplug the external disk anytime we want (just not around midnight).

My crontab:

oliver@bubba:~$ crontab -l
0 0 * * * /home/oliver/shared/scripts/

The script
#! /bin/sh

if mountpoint /mnt/backup; then
  sudo umount /mnt/backup

sudo mount /mnt/backup

if [ $? -eq 0 ]; then

  rsync -avvih --progress \
    --exclude /downloads \
    --exclude /movies \
  /home/storage/ /home/oliver/backup \
  > /tmp/cron_output.log 2>&1


sudo umount /mnt/backup

Symlinks and fstab

Symlink in my home for convenience:

oliver@bubba:~$ ls -l /home/oliver/backup
lrwxrwxrwx 1 oliver users 11 Aug 7 21:38 /home/oliver/backup -> /mnt/backup/

Entry in /etc/fstab:

oliver@bubba:~$ grep "/mnt/backup" /etc/fstab
/usr/local/share/backup /mnt/backup ntfs-3g defaults 0 0

Device symlink /usr/local/share/backup:

oliver@bubba:~$ ls -l /usr/local/share/backup
lrwxrwxrwx 1 root staff 84 Jun 23 01:51 /usr/local/share/backup -> /dev/disk/by-id/usb-WDC_WD50_00BPVT-00HXZT3_FDC0FD500000000FD0FF61A6103926-0:0-part1

Try it manually

/home/oliver/shared/scripts/ &
less /tmp/cron_output.log

Room for improvement

The symlink to the device file is the ugliest part of the whole solution. Currently I have to plug the disk directly into a USB slot on the file server because if I connect it via a USB hub, it will appear under a different name in /dev/disk/by-id and my symlink won’t work. I would like to use a udev rule instead that automatically creates an identical symlink no matter how the the disk is plugged in.

I would also like to implement a 2-way backup so that files we put on the external disk, for example photos from a trip to relatives, will be mirrored to the file server. It should be just another rsync command going in the opposite reaction.

Maybe I would also like the backup process to start right away when the disk is plugged in, in addition to the nightly cron job. This would probably require another udev rule.

Categories: bash, debian Tags: , , , ,