bugs

NFS mount permission denied

Error:

[root@traderdirect ~]# mount 10.93.138.18:/nfs-shares /mounts/tdstorage/
mount: 10.93.138.18:/nfs-shares failed, reason given by server: Permission denied

Solution: /bin/mount -t nfsd nfsd /proc/fs/nfsd See: this bug report

df and du do not match

When a disk is full but nothing shows up as taking up a lot of space (according to du) then it's possible files were deleted before they were closed.

To determine if this is the case, run this command: lsof 2>/dev/null | grep deleted then restart the offending process.

NFS filesystems won't mount

[root@dds-gaprodweb04 ~]# mount -a
mount: wrong fs type, bad option, bad superblock on dsnetapp01-dds:/vol/vol10_dsna1_nas/tol_systems,
      missing codepage or helper program, or other error
      (for several filesystems (e.g. nfs, cifs) you might
      need a /sbin/mount.<type> helper program)
      In some cases useful info is found in syslog - try
      dmesg | tail  or so

Running by hand gives this:

[root@dds-gaprodweb04 ~]# mount -t nfs dsnetapp05-dds:/vol/vol8_dds_gaprodweb_shared_dsna5_nas/www_shared /www/files/ga_shared
mount.nfs: rpc.statd is not running but is required for remote locking.
mount.nfs: Either use '-o nolock' to keep locks local, or start statd.
mount.nfs: an incorrect mount option was specified
[root@dds-gaprodweb04 ~]# yum search rpc

Solution: make sure rpc.statd is running.

Unable to bring up eth0 after cloning

This is annoying. After cloning a centos 6 vm with an active eth0, the interface in the new VM will only work as eth1. To fix it, edit /etc/udev/rules.d/70-persistent-net.rules, and delete the eth1 line.

General

Add New Disk

#scan for disks:
echo "- - -" > /sys/class/scsi_host/host0/scan
fdisk it to create a partition, then mkfs

Resize existing disk

If mounted, unmount
fdisk it, delete the primary partition
fdisk, add new partition
resize2fs /dev/sdc1

Add Swap

TO add a 4 gig swap:

dd if=/dev/zero of=/swapfile bs=1M count=4096
mkswap /swapfile
swapon /swapfile

Then add the following to /etc/fstab:

/swapfile swap swap defaults 0 0

Install Oracle Instant Client

download rpm here
- install it
add /usr/lib/oracle/11.2/client64/lib/ to /etc/ld.so.conf.d/oracle-x86-64.conf
- run ldconfig

Kernel Parameters for Oralce

Put in /etc/sysctl.conf
sysctl -a will list current parameters
sysctl -p /etc/syscth.conf will reload new parameters

kernel.sem = 250 32000 100 128

net.ipv4.ip_local_port_range = 9000 65500
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576
fs.aio-max-nr = 1048576

fs.file-max = 6815744

See more here

Changing hard & soft file limits

Edit /etc/security/limits.conf

Ethernet Interface Details

[root@host ~]# ethtool eth0
Settings for eth0:
        Supported ports: [ TP ]
        Supported link modes:   10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Full 
        Supports auto-negotiation: Yes
        Advertised link modes:  10baseT/Half 10baseT/Full 
                                100baseT/Half 100baseT/Full 
                                1000baseT/Full 
        Advertised auto-negotiation: Yes
        Speed: 1000Mb/s
        Duplex: Full
        Port: Twisted Pair
        PHYAD: 1
        Transceiver: internal
        Auto-negotiation: on
        Supports Wake-on: g
        Wake-on: d
        Link detected: yes

Add EPEL Repo

wget http://download.fedora.redhat.com/pub/epel/5/i386/epel-release-5-4.noarch.rpm
rpm -Uvh epel-release-5-4.noarch.rpm
Edit /etc/yum.repos.d/epel.repo, add priority=3 to the end of the [epel] section

Check High Mem Usage

ps auxf | sort -nr -k 4 | head -10

Set up X11 Forwarding

yum install xorg-x11-apps xorg-x11-xauth xorg-x11-utils
Verify X11Forwarding yes in /etc/ssh/sshd_config
ssh -X hostname

Add NFS export

/etc/exports

/db    dsdevdb02-tol-oracle.traderonline.com(rw)

/etc/sysconfig/iptables

#NFS
-A RH-Firewall-1-INPUT -p udp -m udp --dport 2049 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 2049 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 111 -j ACCEPT

Start services

exportfs -a
service nfs start

Issues

Check selinux
Check that the shared dir is not already an nfs mount from another server
See the Permission Denied bug above
If you get the error nfs mount: mount: /mnt: Not owner, then add o vers=3 to the mount command. Happens with solaris 10 mounting something from centos.

Enable NFS Client

yum install nfs-utils
yum install rpcbind
/etc/init.d/rpcbind start
/etc/init.d/nfslock start
turn those on with chkconfig

SNMP

Disable logging

Add OPTIONS="-Lf /dev/null -p /var/run/snmpd.pid" to /etc/snmp/snmpd.options on centos5, /etc/sysconfig/snmpd on centos 6.

Centos

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