Service Desk Knowledgebase: Linux

This is the Linux content page of the CL Wiki Service Desk Knowledgebase. Its purpose is to provide information to the Service Desk team on how to handle problems and requests about this CL service. If you are involved with the provision of this CL service please feel free to add to the knowledge about that it.

If CL staff need to tell the Service Desk team about problems with this service please email
sys-admin-aside@cl.cam.ac.uk.

Return to the Service Desk Knowledgebase SERVICE PORTFOLIO

Key Service Description & URLs

• Generic Unix/Linux system information
• Computer Laboratory News (Twitter use @UC_CL_SysAdm)

CL Customer Documentation

• ???

Further CL Sys-Admin Resources

• http://www.wiki.cl.cam.ac.uk/rowiki/SysInfo/HelpDesk/Linux - Linux
• http://www.wiki.cl.cam.ac.uk/rowiki/SysInfo/HelpDesk/LinuxSoftware - Adding software packages

Underpinning Services

• ??? - Any supporting or underpinning services

Customer-base for this Service

• Linux boxes are available to all staff and post-graduates, and well as some on the Part III Under-graduates.

Costs

• Hardware is charged for if you are a Research Assistant or a University Teaching Officer, but free to Post-graduates.
• Support is free.

SLA

• ??? - Timeframes or service level agreement for fulfilling the service

Service Desk Call Handling Procedure

• RT tickets can be escalated to the unix-admin by changing the Queue to unix-admin with the Owner set to Nobody & Status set to new. Tell the requestor:
  I am passing this request over to our Unix Admin team who, I'm sure, will be in contact shortly.

Contacts

Primary

• ???@cl.cam.ac.uk (Goes to ???)
• ???@lists.cam.ac.uk (Goes to ???)
• Tel: ???

Other

• Piete Brooks
• David Damerell

Availability

• Monday: 09:00-17:00
• Tuesday: 09:00-17:00
• Wednesday: 09:00-17:00
• Thursday: 09:00-17:00
• Friday: 09:00-17:00
• Saturday: Closed
• Sunday: Closed

Hints, Tips & Known Issues

Clock slew problem

Graham Titmus (3 Feb 2015)

First check if this is a physical machine or a VM. If a physical machine login to it. If a Xen VM then login to the dom0 which hosts the VM, to find that do

cl-onserver --xe cl-vm-status all hid | grep <<machine_name>>

When logged in to the appropriate machine first check if not is working correctly

/usr/sbin/ntpdc -p

which should not look like this

 remote local st poll reach delay offset disp
 =======================================================================
 *LOCAL(0) 127.0.0.1 10 64 377 0.00000 0.000000 0.03046

but have multiple lines each to a remote ntp server.

If it doe slook like above then restart the ntpd service

 cl-asuser service ntpd restart

and check the output again.

Linux user can't login using graphical interface

Graham Titmus (13 Jan 2015)

Symptoms: Linux user can't login using graphical interface, they enter username and password and get a blank screen then back to login

A common cause of this is a failure to access the home directory stored on the File Server (AKA Elmer or Filer), X (the window manager) needs to write a file there when it starts the user session. To diagnose if this is the problem do the following:-

1. Remote login to the machine using ssh -K hostname@cl.cam.ac.uk from a CL machine - check if your home directory is present (ls -al ~). If is is look to see if the users home directory is present (ls -al ~crsid).
2. If the home directory is missing then try to restart the auto mounter (cl-asuser service autofs restart).
3. Look at the mounted filesystems (grep ldap /proc/mounts - will show which systems have been auto mounted using data form the LDAP).

An alternative is to ask the user to check if it is the machine failing to log them in or a problem with X by getting them to try on the text console (Select with Ctrl-Alt-F2). If they can login there but have no home then it is probably a problem with the filesystem. If they cannot login at all then it is an authentication problem. They should then try from another machine that is known to work to check their login works.

Adding privileged users

Machines are normally setup with the 'assigned user' having both 'cl-asuser' and 'sudo' access. They can use the latter to grant privs to other users, the former (if ACLs are enabled) using

sudo setfacl -m u:$user:rw /etc/user-config/bundles

where $user should be replaced by the crsid of the person who is to be granted privilege.

The latter by adding them to the relevant group (e.g. sudo or root) in /etc/group. cl-asuser privs should be available immediately, sudo will only take effect in new sessions. If there are sudo problems use groups to check which groups the user is in, and "sudo -l" to check the status. Check /etc/sudoers and /etc/sudoers.d/* to check which groups give ALL access.

If the assigned user has not been setup (because a machine has been moved to a new user or was not done when the machine was installed do

cl-asuser cl-hostid-fix --user <<crsid>> -a

Categorising Keywords

• Linux Ubuntu PC Person Computer