In Ubuntu can root overwrite any file?

Question

I am on Ubuntu 10.04.02. I thought that when using sudo that would execute commands as root. But here as root I cannot write to my own file. Is this correct?

david@ubuntu:/var/www/system/paydaydebt/log$ ls -l
total 16
-rw-r--r-- 1 root root   32 2011-08-27 01:00 cron_daily.log
-rw-r--r-- 1 root root 5082 2011-08-27 20:45 cron_email.log
-rw-r--r-- 1 root root  429 2011-08-27 20:00 cron_hourly.log
david@ubuntu:/var/www/system/paydaydebt/log$ sudo date >> cron_email.log
-bash: cron_email.log: Permission denied

david@ubuntu:/var/www/system/paydaydebt/log$ sudo chmod 664 cron_email.log
david@ubuntu:/var/www/system/paydaydebt/log$ ls -l
total 16
-rw-r--r-- 1 root root   32 2011-08-27 01:00 cron_daily.log
-rw-rw-r-- 1 root root 5082 2011-08-27 20:45 cron_email.log
-rw-r--r-- 1 root root  429 2011-08-27 20:00 cron_hourly.log
david@ubuntu:/var/www/system/paydaydebt/log$ sudo date >> cron_email.log
-bash: cron_email.log: Permission denied

david@ubuntu:/var/www/system/paydaydebt/log$ sudo chmod 666 cron_email.log
david@ubuntu:/var/www/system/paydaydebt/log$ ls -l
total 16
-rw-r--r-- 1 root root   32 2011-08-27 01:00 cron_daily.log
-rw-rw-rw- 1 root root 5082 2011-08-27 20:45 cron_email.log
-rw-r--r-- 1 root root  429 2011-08-27 20:00 cron_hourly.log
david@ubuntu:/var/www/system/paydaydebt/log$ sudo date >> cron_email.log

david@ubuntu:/var/www/system/paydaydebt/log$ sudo chmod 644 cron_email.log
david@ubuntu:/var/www/system/paydaydebt/log$ ls -l
total 16
-rw-r--r-- 1 root root   32 2011-08-27 01:00 cron_daily.log
-rw-r--r-- 1 root root 5111 2011-08-27 20:47 cron_email.log
-rw-r--r-- 1 root root  429 2011-08-27 20:00 cron_hourly.log
david@ubuntu:/var/www/system/paydaydebt/log$ sudo date >> cron_email.log
-bash: cron_email.log: Permission denied
david@ubuntu:/var/www/system/paydaydebt/log$

enter image description here

I think this is a question for superuser.com. – Ricardo Polo Jaramillo Aug 28 '11 at 01:06 — Ricardo Polo Jaramillo, Aug 28 '11 at 01:06

score 13 · Accepted Answer · answered Aug 28 '11 at 01:02

13

sudo only applies to the command run; your append >> occurs as the current user.

answered Aug 28 '11 at 01:02

Shane Madden

115,228

4

so, as a workaround you could do something like: sudo sh -c 'date >> cron_email.log' – Chad Feller Aug 28 '11 at 01:07
1

That is probably the best option. At that point, though, it would be simpler just to sudo su - :) – Rilindo Aug 28 '11 at 01:11
1

"sudo su" is useless use of su. just do "sudo -s" – allo Sep 02 '11 at 22:34

score 1 · Answer 2 · answered Aug 30 '11 at 20:33

Best solution: run "sudo program|sudo tee -a output_file >/dev/null"

tee writes to file and stdout, >/dev/null redirects the output to /dev/null (just discards it) and the -a option tells tee to append to the file (as >> does) instead of overwriting the file (as > does).

run a simple command with sudo first, so the password gets cached, because otherwise you get two password-prompts on the same line and need to answer both before being able to continue.

In Ubuntu can root overwrite any file?

2 Answers2