1. List all services enabled/disabled on boot (ex chkconfig –list)
systemctl list-unit-files
2. Enable HTTPD + Mysql service on system boot:
systemctl enable httpd systemctl enable mariadb
3. Reverting to iptables from firewalld
systemctl stop firewalld systemctl mask firewalld yum install iptables-services systemctl enable iptables systemctl start iptables # to save iptables rules use service iptables save
By default, most Linux Installers create separate /home partition, occupying most of the drive space.
When server is used mostly for system services, you may transfer free space from /home partition to /root.
Before adjustment we have 98% filled root partition and 141GB free space on /home, which we would like to use:
[root@oracle ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_oracle-lv_root
50G 1G 50G 98% /
tmpfs 630M 0 630M 0% /dev/shm
/dev/cciss/c0d0p1 477M 106M 346M 24% /boot
/dev/mapper/vg_oracle-lv_home
149G 60M 141G 1% /home
1. First step is to unmount /home partition
umount /home
System may refuse to unmount /home if you have users logged on to the box or services running from /home. After logging off / stopping services command should succeed.
2. Shrink old /home partition to 20GB, (system will force you to check filesystem for errors by running e2fsck)
e2fsck -f /dev/mapper/vg_oracle-lv_home resize2fs /dev/mapper/vg_oracle-lv_home 20G
3. Reduce the LVM to 20G
lvreduce -L 20G /dev/mapper/vg_oracle-lv_home
4. Extend /root LVM to new size, utilizing 100% of free space on disk
lvextend -l +100%FREE /dev/mapper/vg_oracle-lv_root
5. Grow /root (ext3/4) partition to new LVM size
resize2fs /dev/mapper/vg_oracle-lv_root
6. Mount /home
mount /home
Result
[root@oracle ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_oracle-lv_root
178G 50G 128G 28% /
tmpfs 630M 0 630M 0% /dev/shm
/dev/cciss/c0d0p1 477M 106M 346M 24% /boot
/dev/mapper/vg_oracle-lv_home
20G 45M 19G 1% /home
After these simple steps we have 72% of free disk space of root partition.
TL;DR
Resizing /home partition (/dev/mapper/vg_oracle-lv_home) to 20GB and transfering remaining space to /root (/dev/mapper/vg_oracle-lv_root):
umount /home e2fsck -f /dev/mapper/vg_oracle-lv_home resize2fs /dev/mapper/vg_oracle-lv_home 20G lvreduce -L 20G /dev/mapper/vg_oracle-lv_home lvextend -l +100%FREE /dev/mapper/vg_oracle-lv_root resize2fs /dev/mapper/vg_oracle-lv_root mount /home
After migrating Current website to Debian 6, PHP calls exec and system stopped working.
The reason for it is debian package dash which modifies behaviour of system default shell:
# ls -l /bin/sh lrwxrwxrwx 1 root root 4 Dec 9 20:25 /bin/sh -> dash
To revert this this behaviour to standard, execute
# dpkg-reconfigure dash
Select “No” and default shell will be changed to standard bash.
You can check it with following command:
# ls -l /bin/sh lrwxrwxrwx 1 root root 4 Dec 9 20:26 /bin/sh -> bash
In recent CentOS version 6.3 is an unresolved bug, which causes the network card to freeze the server.
Following message appears in /var/log/messages
kernel: e1000e 0000:02:00.0: eth0: Error reading PHY register
To work around the problem you will need to turn off Active-State Power Management (ASPM)
(Feature that saves power in the Peripheral Component Interconnect Express (PCI Express or PCIe) subsystem by setting a lower power state for PCIe links when the devices to which they connect are not in use)
For GRUB bootloader edit the following file: /boot/grub/grub.conf and append pcie_aspm=off to the end of kernel boot line.
For example:
kernel /vmlinuz-2.6.32-279.el6.x86_64 ro root=UUID=81e9e0a2-0a51-4d75-955d-909aaf848192 rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 crashkernel=auto rd_NO_DM rd_MD_UUID=c6855f45:016a63bb:2d79bfb2:07371ed8 rd_NO_LVM rd_MD_UUID=5d5a434e:6c20cfcd:51340c3f:29c29151 pcie_aspm=off
To verify the change, reboot the server and run the following command:
dmesg | grep PCIe PCIe ASPM is disabled
If your output is different, the change in grub.conf did not take an effect.
To add default route via VPN server add following lines into your server’s configuration file (usually /etc/openvpn/server.conf).
push "redirect-gateway def1" push "dhcp-option DNS 8.8.8.8"
DNS option may be required, if you are having troubles with name resolution after connecting to VPN.
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