Add static route to linux

add a remote host

remote host 192.168.1.20
local gateway 10.1.1.20
route add -host 192.168.1.20 gw 10.1.1.20

add a remote network

route add -net 192.168.98.42 netmask 255.255.255.255 gw 192.168.99.1

check the route 

route -n

Delete a route

route del -net 10.41.41.0 netmask 255.255.255.0 gw 10.41.42.8

route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0

adds a route to the network 192.56.76.x via "eth0". The Class C netmask modifier is not really necessary here because 192.* is a Class C IP address. The word "dev" can be omitted here.

To make the routing information persistent, add the “route add” line as seen above into the /etc/rc.local file.
Sample /etc/rc.local file.
or /etc/rc.d/rc.local

touch /var/lock/subsys/local
route add -net 10.41.41.0 netmask 255.255.255.0 gw 10.41.42.8


 

Error : Root File System Is Read-Only | linux based file system become read only

As a workaround, remount the Linux file system using this command to return it to the proper state:

 

mount -o remount /

Remount it. If /etc/fstab is correct, you can simply type:

mount -n -o remount /

If /etc/fstab is wrong, you must give the device name and possibly the
type, too: e.g.

mount -n -o remount -t ext2 /dev/hda2 /

VMware has identified a problem where file systems may become read-only after encountering busy I/O retry or SAN or iSCSI path failover errors.

 

The same behavior is expected even on a native Linux environment, where the time required for the file system to become read-only depends on the number of paths available to a particular target, the multi-path software installed on the operating system, and whether the failing I/O was to an EXT3 Journal. However, the problem is aggravated in an ESX host environment because ESX host manages multiple paths to the storage target and provides a single path to the guest operating system, which effectively reduces the number of retries done by the guest operating system.

 

These guest operating systems are affected:

• RHEL5 (RedHat)
• RHEL4 U6
• RHEL4 U4
• RHEL4 U3
• SLES10
• SLES9 SP3
• Ubuntu 7.04 
  
  Note: This issue may affect other Linux distributions based on early 2.6 kernels as well, such as Ubuntu 7.04.