1. How to get users list in a linux machine.
As local user
# cat /etc/passwd
- Seperated by username, password, UID, GID, home directory, shell
# cat /etc/group
- Use this to see group information.
- This handles everything nsswitch.conf does (NIS, LDAP, xyzzy, whatever).
getent passwd cut -d: -f1 sort -u
- To get just a list of usernames
2. To check what is the IP address of the DHCP server where assigned IP leased from:
For CentOS 5, the command:
# grep dhcp-server-identifier /var/lib/dhclient/dhclient-eth0.leases
or for CentOS 4, the command:
# grep dhcp-server-identifier /var/lib/dhcp/dhclient-eth0.leases
To list all PCI device:
To determine the change log of installed software:
rpm -qi –changelog
yum install yum-changelog
repoquery –changelog foo
3. Robert Moskowitz Tips on Private Network IP Addresses:
If you use addresses from the 192.168 range, avoid the nets:
192.168.0.0, 192.168.1.0, 192.168.2.0, and 192.168.100.0 These are commonly used by various ‘appliances’. Choose something ‘wierd’ like 192.168.49.0 (or some other prime number less than 255). Though I tend to use 192.168.64.0, 192.168.96.0, or 192.168.128.0
Also avoid the 172.16 and 10. ranges. These are commonly used in Company internal private networks, and if you want to ‘VPN’ to them, it an cause unwanted results (like it won’t work).
This is general advice to anyone using private addresses for small usages.
4. To Get Memory Usage and Information:
free - for summary information
cat /proc/meminfo - for detailed information
5. To get hardware info:
6. To test for disk I/O performance:
Download ‘disktest’ utility from Linux Test Project(LTP) and do the ff:
disktest -B 4k -h 1 -I BD -K 4 -p l -P T -T 300 -r /dev/sdX
disktest -B 4k -h 1 -I BD -K 4 -p l -P T -T 300 -w /dev/sdX
disktest -B 4k -h 1 -I BD -K 4 -p r -P T -T 300 -r /dev/sdX
disktest -B 4k -h 1 -I BD -K 4 -p r -P T -T 300 -w /dev/sdX
Description of the options used:
-B 4k = 4k block ios
-h 1 = 1 second heartbeat
-I BD = block device, direct io
-K 4 = 4 threads, or 4 outstanding/overlapping ios, typical pattern
(use -K 1 for the raw performance of single drive, aka dd type output)
-P T = output metrics type “Throughput”
-T 300 = duration of test 300 seconds
-r = read
-w = write
These tests will run across the whole disk/partition and the write
tests WILL BE DESTRUCTIVE so be warned!
7. To determine PCI information and replacing LAN card info:
Put or replace alias entries for LAN card and restart network.
8. To get driver info: