Hot-add Memory to Linux Guest in VMware
Symptoms
Memory you have hot added in Linux guest virtual machines is not registered using the free or top commands.
Cause
This issue occurs when Linux requires manual intervention to expose the newly added memory in the guest. The process is called setting the memory to online.
Resolution
To resolve this issue, set the memory online in RHEL/CentOS, and Ubuntu/Debian.
Verify if the operating system actually sees the newly added memory:
grep -i MemTotal /proc/meminfo
Look for memory that appears offline (to tools like free and top):
grep line /sys/devices/system/memory/*/state
Use the following shell script to set all memory files to online:
for RAM in $(grep line /sys/devices/system/memory/*/state)
do
echo "Found ram: ${RAM} ..."
if [[ "${RAM}" == *":offline" ]]; then
echo "Bringing online"
echo $RAM | sed "s/:offline$//"|sed "s/^/echo online > /"|source /dev/stdin
else
echo "Already online"
fi
done
You can run the script twice and you should see similar output:
Found ram: /sys/devices/system/memory/memory0/state:online ... Already online Found ram: /sys/devices/system/memory/memory10/state:online ... Already online Found ram: /sys/devices/system/memory/memory11/state:online ... Already online Found ram: /sys/devices/system/memory/memory12/state:online ... Already online Found ram: /sys/devices/system/memory/memory13/state:online ... Already online Found ram: /sys/devices/system/memory/memory14/state:online ... Already online Found ram: /sys/devices/system/memory/memory15/state:online ... Already online Found ram: /sys/devices/system/memory/memory1/state:online ... Already online Found ram: /sys/devices/system/memory/memory2/state:online ... Already online Found ram: /sys/devices/system/memory/memory3/state:online ... Already online Found ram: /sys/devices/system/memory/memory4/state:online ... Already online Found ram: /sys/devices/system/memory/memory5/state:online ... Already online Found ram: /sys/devices/system/memory/memory6/state:online ... Already online Found ram: /sys/devices/system/memory/memory7/state:online ... Already online Found ram: /sys/devices/system/memory/memory8/state:online ... Already online Found ram: /sys/devices/system/memory/memory9/state:online ... Already online
Or you can manually update each file when memory appears offline:
echo online >/sys/devices/system/memory/memory[number]/state
Verify you can see the extra memory by running this command:
free -m
Turn On all Available Guest vCPU and Memory
The script below will turn on all available vCPU and memory on your VM:
#!/bin/bash
# Based on script by William Lam - http://engineering.ucsb.edu/~duonglt/vmware/
# Bring CPUs online
for CPU in $(ls /sys/devices/system/cpu/ |grep -E '(cpu[0-9])')
do
CPU_DIR="/sys/devices/system/cpu/${CPU}"
echo "Found cpu: \"${CPU_DIR}\" ..."
CPU_STATE_FILE="${CPU_DIR}/online"
if [ -f "${CPU_STATE_FILE}" ]; then
STATE=$(cat "${CPU_STATE_FILE}" | grep 1)
if [ "${STATE}" == "1" ]; then
echo -e "\t${CPU} already online"
else
echo -e "\t${CPU} is new cpu, onlining cpu ..."
echo 1 > "${CPU_STATE_FILE}"
fi
else
echo -e "\t${CPU} already configured prior to hot-add"
fi
done
# Bring all new Memory online
for RAM in $(grep line /sys/devices/system/memory/*/state)
do
echo "Found ram: ${RAM} ..."
if [[ "${RAM}" == *":offline" ]]; then
echo "Bringing online"
echo $RAM | sed "s/:offline$//"|sed "s/^/echo online > /"|source /dev/stdin
else
echo "Already online"
fi
done
Source & credit: http://www.supermaru.com/2016/10/hot-add-cpu-memory-ubuntu-guest-vmware/
