I set the following values (-1 will be resolved to unlimited, I suppose) in /etc/security/limits.conf (CentOS 6.2)

root nofile soft -1

root nofile hard -1

and I can't log in with root user now. Similar to the issue described here. Setting the value back would resolve the issue.

Can anyone help to explain this ?


Thanks guys. I memorize my settings incorrectly. Those values should be

root soft nofile -1
root hard nofile -1

3 Answers 3


As @Michael Hampton told you, your syntax is wrong, but anyway i don't think is good idea to set the file limit to unlimited

You can read this post for more information https://stackoverflow.com/questions/1212925/on-linux-set-maximum-open-files-to-unlimited-possible

I downloaded the kernel version linux- and i saw this from kernel/sys.c:

 SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
    struct rlimit new_rlim, *old_rlim;
    int retval;

    if (resource >= RLIM_NLIMITS)
            return -EINVAL;
    if (copy_from_user(&new_rlim, rlim, sizeof(*rlim)))
            return -EFAULT;
    if (new_rlim.rlim_cur > new_rlim.rlim_max)
            return -EINVAL;
    old_rlim = current->signal->rlim + resource;
    if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
            return -EPERM;
    if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
            return -EPERM;

from man proc

The kernel constant NR_OPEN imposes an upper limit on the value that may be placed in 

from ./fs/file.c:

./fs/file.c:30:int sysctl_nr_open __read_mostly = 1024*1024;
echo $((1024*1024))

why you need more files than nr_open?

i did a test using your limits.conf settings:


 egrep -v "^#|^$" /etc/pam.d/su
 auth       sufficient pam_rootok.so
 session       required   pam_env.so readenv=1
 session       required   pam_env.so readenv=1 envfile=/etc/default/locale
 session    optional   pam_mail.so nopen
 session    required   pam_limits.so 
 @include common-auth
 @include common-account
 @include common-session

Now i'll to switch to user root using su command:

root@ubuntu:~# strace -e setrlimit su - root
setrlimit(RLIMIT_NOFILE, {rlim_cur=RLIM64_INFINITY, rlim_max=RLIM64_INFINITY}) = -1 EPERM (Operationnot permitted)

You've reversed the second and third fields.

It should read instead:

root soft nofile -1
root hard nofile -1

The number you set in for nofile (number of open files) cannot be greater than the value found in /proc/sys/fs/nr_open. Check that file and use that value.

[root]# cat /proc/sys/fs/nr_open 1048576 [root]# cat /etc/security/limits.d/biguser.conf biguser - nofile 1048576

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.