Raj Kiran Grandhi <grajkiran@gmail.com> writes:
Haines Brown wrote:
I have a script, ~/scripts/backup, owned by root, that mounts an
external UPS drive, creates a directory based on date, and backs up my
hard disk with the exception of a few directories.
I created a symlink to /etc/cron.weekly to automate the job, but
because the script is located in user's directory, it runs with user's
permission, and much of the backup has "permission denied".
I am unable to reproduce this. Symbolic links in the /etc/cron.hourly
directory run as root irrespective of where the link points to. In my
case, the scripts were not even owned by root and were in a user's
home directory. Place a link to the following script and examine its
output:
### Start of script
#!/bin/bash
echo "UID=$UID; EUID=$EUID"
env
### End of script
I tried this, and it works. That is, I created a test script owned by
user in ~/brownh/scripts and symlinked it to /etc/chron.hourly (I'm running
Debian Etch), and sure enough, chron sent me this message:
/etc/cron.hourly/test:
UID=0; EUID=0
SHELL=/bin/sh
PATH=/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin
PWD=/
LANG=en_US.UTF-8
HOME=/root
SHLVL=2
LOGNAME=root
_=/usr/bin/env
I'm not sure what this suggests. If I do:
$ ~/scripts/test
UID=1000; EUID=1000
SSH_AGENT_PID=8645
TERM=xterm
SHELL=/bin/bash
HUSHLOGIN=FALSE
WINDOWID=35651597
USER=brownh
...
This suggests that when user runs the script. the script has the
powers of user, but when root runs it (symlink from /etc/cron.hourly)
it runs as root commands. That is, if I am root and do:
# ~/scripts/backup
I get a complete backup. If I run as user or if cron.weekly runs it by
means of a symlink, it is a partial backup of only those directories
accessible by user.
So I tried to start the script with this snippet:
pw=<password>
sudo
echo $pw
which does not work. I have several questions:
b) Why does the script snippet above not work?
In the snippet above the echo command is run _after_ the sudo command
completes. You probably wanted to pass the password to the standard
input of the sudo command. You can try using a pipe for that, like:
echo $pw|sudo /path/to/your/backup-script
Understood, but the problem is that I'm trying to get the commands in
the backup script to have the permission of root. had I assumed that a
symlink in /etc/cron.weekly pointing to a backup script would have no
permissions problem.
Here's the backup script in its entirely that fails to work in the
sense that cron reports permission denied for directories requring
root permission to cpio. I don't see that the little echo routine does
anything, but I'm putting this backup script symlink into
/etc/cron.hourly to see what happens.
pw=<password>
echo $pw | sudo
sudo mount /media/mirror
dirName=`date +%F`
sudo mkdir /media/mirror/"$dirName"
sudo find / -print | egrep -v "^/media|^/proc|^/sys" | cpio -pdmuv /media/mirror/"$dirName" 2>&1 | cat -vt
echo $pw | sudo
sudo umount /media/mirror
exit 0