slow/delay in ssh login at Solaris/Linux

well, you might have notice when you access some UNIX machine, you will see a bit delay in login process, it can hang for a while at different levels such as,

1. Before asking username/login prompt
2. After asking username/login prompt
3. After taking password.

interestingly on all three cases the culprit is your DNS/name-resolution service.

Solutions:

1. mostly probably your DNS is not accessible or unable to resolve remote host's hostname.

2. if DNS is working then your host file is the issue! it should be correctly written.

3. check your client/workstation hostname is resolvable at server.

3rd is really tricky as if /etc/ssh/sshd_config is configured to ask for reverse dns (rDNS) request server will try to resolve client/workstation's hostname at server, and if your DNS is not configured to resolve client-side machine hostname, you will get delay on login.

The easiest solution to all login delay would be editing /etc/ssh/sshd_config and disbaling "useDNS" parameter by setting it "useDNS no".

cheers

Solaris boot sequence chart

I found this boot chart for opensolaris at EREMIN blog, for sure has a worth to read.


cheers

Fix! FATAL: system is not bootable, boot command is disabled

When i was trying to login through Serial Port on our RAC test machines to boot them in single user mode, i got following error i.e.

Err:

FATAL: system is not bootable, boot command is disabled

Cause:

I broke in console prompt before memory initialization completed !

Solution:

{1} ok printenv auto-boot?
auto-boot? = true
{1} ok setenv auto-boot? false
auto-boot? = false
{1} ok reset-all

cheers

Fix, /opt/iplanet/ldap/slapd-hostname/start-slapd: not found

Eric reported me slow login on Solaris 10 machines, i started my investigation from name resolution & i found that the machine was unable to resolve hostname(s) from DNS. initially i was expecting some kind of misconfiguration of resolv.conf but lately i found that DNS server of that environment was down!

So i simply shoot

#svcadm -v restart network/iplanetldap

but found that service did'nt started :(

anyhow with further investigation i found following,

Symptoms:

when you will run svcadm -v restart network/iplanetldap you will get following error in log file i.e.

Error:

# cat /var/svc/log/network-iplanetldap:default.log

[ Oct 18 23:02:34 Executing start method ("/opt/iplanet/ldap/slapd-hostname/start-slapd") ]
/sbin/sh: /opt/iplanet/ldap/slapd-hostname/start-slapd: not found

Hint:

HOSTNAME in error was wrong! so i found the cause, that somehow ldap daemon startup script is not getting correct hostname of the machine.

Fix:

Run following command to check store configuration for ldap daemon.

Step 01: #svccfg export network/iplanetldap > /tmp/ldap-old-config.xml

this will create a file “/tmp/ldap-old-config.xml” you should vi/edit this file & correct hostname inside.

Output of the file is:

bash-3.00# vi /tmp/ldap-old-config.xml

edit following lines:

name='start' type='method' exec='/opt/iplanet/ldap/slapd-hostname/start-slapd' timeout_seconds='60'
name='stop' type='method' exec='/opt/iplanet/ldap/slapd-hostname/stop-slapd' timeout_seconds='60'


Step 02: svccfg import /tmp/ldap-old.xml

Step 03: svcadm -v restart network/iplanetldap

Step 04: svcadm -v clear network/iplanetldap

Step 05: svcs -l network/iplanetldap

cheers

System Administration Best Practices for System Admin Team

After joining System Administrator team, i found that we lack a lot of best practices & then started my research on what could be the best practice guidelines for system administrators... unfortunately i was unable to get any serious & well written sysadmin best practice guide. So finally i decided to write my own :)

this document is not final word from sysadmin world, there may be some best practice points missing, i would appreciate, if you can come up with your suggestions for improvement of this document.

Download:

cheers

Confidence!

sometimes when i am surfing through blogs, i get inspired by people who share their small yet heavily weighted thoughts...same happen when i read Vin Diesel facebook blog post!

"Confidence is the most important thing you can teach someone... if you can teach them confidence, you don't have to teach them anything else."

i agree with his father!

cheers

gunzip, uncompress file.gz to another/different directory

Ariel asked me to help him in unzipping his file.gz which is on a directory/disk that has no space to unzip, he wanted unzip to another directory/disk which had enough space to house unzipped files.

initially i was checking gunzip manual but didn't found any option to do this kind of task, though at freenode someone told me to use zcat instead of gunzip! e.g.

$zcat filename.gz > /path/to/unzipped/file

so sometimes instead of reading command's manual we need to check command's capabilities ;)

cheers