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I'm using CentOS and Red Hat Enterprise Linux on a few machines without the GUI. How can I check if recently installed updates require a reboot? In Ubuntu, I'm used to checking if /var/run/reboot-required is present.

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5 Answers 5

up vote 6 down vote accepted

You could compare the ouput of uname -a with the list of installed kernel packages

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Is a different kernel the only reason a linux server would need a reboot? – Chris_K Mar 16 '10 at 15:57
Normally, when staying within the 'normal' package upgrade processes (up2date, yum etc.), there shouldn't be really many other reasons to reboot the system besides the kernel upgrade – Dominik Mar 19 '10 at 14:35
I suspect that certain other packages may require a reboot eben iof the kernel does not change (when I installed kexec-tools-2.0.0-258 on centos6.0 there was no memory reserved for the dump) – nhed Aug 29 '13 at 19:25
BeyondTrust's pbis-open package requests the user to reboot after installation via stdout. – bshacklett Feb 13 at 19:41

About comparing installed kernels with running one:

LAST_KERNEL=$(rpm -q --last kernel | perl -pe 's/^kernel-(\S+).*/$1/' | head -1)
CURRENT_KERNEL=$(uname -r)


Hope that helps!

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At first I thought this wasn't working as it continued to tell me to reboot after I had, but then found out that if you are using a DigitalOcean instance, you need to manually change the kernel from their control panel first before rebooting. – Programster Aug 17 '14 at 12:12

One thing that can be helpful to look at in terms of "is a reboot required" is whether or not there are any files that have been removed/replaced by the update but for which the old files are still loaded/used by active processes.

Basically, when YUM updates a file that is in use by a process, the file itself may have been marked for deletion, but the process keeps using the old file since it has an open file-descriptor to the old file's inode.

A command to get a count of the number of old files still in use:

#lsof | grep "(path inode=.*)" | wc -l

That command will give you a count of the files.

Use this instead to see which files are actually in use:

#lsof | grep "(path inode=.*)"

That command will produce output similar to the following on a YUM-updated box:

sshd      3782   root  mem       REG   8,17          153427 /lib64/ (path inode=153253)
mysqld    3883  mysql  mem       REG   8,17          153259 /lib64/ (path inode=153402)
mingetty  4107   root  mem       REG   8,17          153243 /lib64/ (path inode=153222)
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Check whether running kernel is the latest one.

If it's not, check whether system was restarted since kernel install.

If it was not, reboot.

CURRENT_KERNEL="$(rpm -q kernel-$(uname -r))"
test -z "$CURRENT_KERNEL" && exit 0     # Current kernel is a custom kernel

LATEST_KERNEL="$(rpm -q kernel | tail -1)"
test -z "$LATEST_KERNEL" && exit 0      # No kernel package installed

LATEST_KERNEL_INSTALLTIME=$(rpm -q kernel --qf "%{INSTALLTIME}\n" | tail -1)
test -z "$LATEST_KERNEL_INSTALLTIME" && exit 1      # Error reading INSTALLTIME

test "$CURRENT_KERNEL" = "$LATEST_KERNEL" && exit 0 # Latest kernel running, no reboot needed

BOOTTIME="$(sed -n '/^btime /s///p' /proc/stat)"
test -z "$BOOTTIME" && exit 1           # Error reading BOOTTIME

test "$LATEST_KERNEL_INSTALLTIME" -lt "$BOOTTIME" && exit 1 # Latest kernel not running, but system was restarted already
                                        # User switched back to an old kernel?

echo reboot
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This doesn't work if you have a PAE enabled kernel version. The uname -r comamnd returns the PAE suffix after the .elX part but not the rpm names. – Yanick Girouard Sep 13 '13 at 15:41

install.log install.log.syslog yum.log you check this place what all got new rpm got install

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