crontab cronjob failed with date single apostrophe date +%d-%b-%Y-%H-%M on linux

August 4th, 2014

I tried to creat one linux cronjob today, and want to note down date & time when the job was running, and here's the content:

echo '10 10 * * 1 root cd /var/log/ovm-manager/;tar zcvf oc4j.log.`date +%m-%d-%y`.tar.gz oc4j.log;echo "">/var/log/ovm-manager/oc4j.log' > /etc/cron.d/oc4j

However, this entry failed to run, and when check log in /var/log/cron:

Aug 4 06:24:01 testhost crond[1825]: (root) RELOAD (cron/root)
Aug 4 06:24:01 testhost crond[1825]: (root.bak) ORPHAN (no passwd entry)
Aug 4 06:25:01 testhost crond[28376]: (root) CMD (cd /var/log/ovm-manager/;tar zcvf oc4j.log.`date +)

So, the command was intercepted and that's the reason for the failure.

Eventually, I figured out that cron treats the % character specially (it is turned into a newline in the command). You must precede all % characters with a \ in a crontab file, which tells cron to just put a % in the command. And here's the updated version:

echo '10 10 * * 1 root cd /var/log/ovm-manager/;tar zcvf oc4j.log.`date +\%m-\%d-\%y`.tar.gz oc4j.log;echo "">/var/log/ovm-manager/oc4j.log' > /etc/cron.d/oc4j

This time, the job got ran successfully:

Aug 4 06:31:01 testhost crond[1825]: (root) RELOAD (cron/root)
Aug 4 06:31:01 testhost crond[1825]: (root.bak) ORPHAN (no passwd entry)
Aug 4 06:31:01 testhost crond[28503]: (root) CMD (cd /var/log/ovm-manager/;tar zcvf oc4j.log.`date +%m-%d-%y`.tar.gz oc4j.log;echo "">/var/log/ovm-manager/oc4j.log)


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resolved – Kernel panic – not syncing: Attempted to kill init

July 29th, 2014

Today when I tried to poweron one VM hosted on XEN server, the following error messages prompted:

Write protecting the kernel read-only data: 6784k
Kernel panic - not syncing: Attempted to kill init! [failed one]
Pid: 1, comm: init Not tainted 2.6.32-300.29.1.el5uek #1
Call Trace:
[<ffffffff810579a2>] panic+0xa5/0x162
[<ffffffff8109b997>] ? atomic_add_unless+0x2e/0x47
[<ffffffff8109bdf9>] ? __put_css_set+0x29/0x179
[<ffffffff8145744c>] ? _write_lock_irq+0x10/0x20
[<ffffffff81062a65>] ? exit_ptrace+0xa7/0x118
[<ffffffff8105b076>] do_exit+0x7e/0x699
[<ffffffff8105b731>] sys_exit_group+0x0/0x1b
[<ffffffff8105b748>] sys_exit_group+0x17/0x1b
[<ffffffff81011db2>] system_call_fastpath+0x16/0x1b

This is quite weird as it's ok yesterday:

Write protecting the kernel read-only data: 6784k
blkfront: xvda: barriers enabled (tag) [normal one]
xvda: detected capacity change from 0 to 15126289920
xvda: xvda1 xvda2 xvda3
blkfront: xvdb: barriers enabled (tag)
xvdb: detected capacity change from 0 to 16777216000
xvdb: xvdb1
Setting capacity to 32768000
xvdb: detected capacity change from 0 to 16777216000
kjournald starting. Commit interval 5 seconds
EXT3-fs: mounted filesystem with ordered data mode.
SELinux: Disabled at runtime.
type=1404 audit(1406281405.511:2): selinux=0 auid=4294967295 ses=4294967295

After some checking, I found that this OVS server was hosting more than 40 VMs, and the VCPUs was tight. So I turned off some unused VMs and then issue resolved.

yum install specified version of packages

July 15th, 2014

Assume that you want to install one specified version of package, say glibc-2.5-118.el5_10.2.x86_64:

[root@centos-doxer ~]# yum list|grep glibc
glibc.i686 2.5-107.el5_9.4 installed
glibc.x86_64 2.5-107.el5_9.4 installed
glibc-common.x86_64 2.5-107.el5_9.4 installed
glibc-devel.i386 2.5-107.el5_9.4 installed
glibc-devel.x86_64 2.5-107.el5_9.4 installed
glibc-headers.x86_64 2.5-107.el5_9.4 installed
compat-glibc.i386 1:2.3.4-2.26 el5_latest
compat-glibc.x86_64 1:2.3.4-2.26 el5_latest
compat-glibc-headers.x86_64 1:2.3.4-2.26 el5_latest
glibc.i686 2.5-118.el5_10.2 el5_latest
glibc.x86_64 2.5-118.el5_10.2 el5_latest
glibc-common.x86_64 2.5-118.el5_10.2 el5_latest
glibc-devel.i386 2.5-118.el5_10.2 el5_latest
glibc-devel.x86_64 2.5-118.el5_10.2 el5_latest
glibc-headers.x86_64 2.5-118.el5_10.2 el5_latest
glibc-utils.x86_64 2.5-118.el5_10.2 el5_latest

Then you should execute glibc-2.5-118.el5_10.2.x86_64. The format of this command is yum install <packagename>-<version>.<platform, such as x86_64>.

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linux process accounting set up

July 8th, 2014

Ensure package psacct is installed and make it boot with system:

rpm -qa|grep -i psacct
chkconfig psacct on
service psacct start

Here're some useful commands

[root@qg-dc2-tas_sdi ~]# ac -p #Display time totals for each user
emcadm 0.00
test1 2.57
aime 37.04
oracle 32819.22
root 12886.86
testuser 1.47
total 45747.15

[root@qg-dc2-tas_sdi ~]# lastcomm testuser #Display command executed by user testuser
top testuser pts/5 0.02 secs Fri Jul 4 03:59
df testuser pts/5 0.00 secs Fri Jul 4 03:59

[root@qg-dc2-tas_sdi ~]# lastcomm top #Search the accounting logs by command name
top testuser pts/5 0.03 secs Fri Jul 4 04:02

[root@qg-dc2-tas_sdi ~]# lastcomm pts/5 #Search the accounting logs by terminal name pts/5
top testuser pts/5 0.03 secs Fri Jul 4 04:02
sleep X testuser pts/5 0.00 secs Fri Jul 4 04:02

[root@qg-dc2-tas_sdi ~]# sa |head #Use sa command to print summarizes information(e.g. the number of times the command was called and the system resources used) about previously executed commands.
332 73.36re 0.03cp 8022k
33 8.76re 0.02cp 7121k ***other*
14 0.02re 0.01cp 26025k perl
7 0.00re 0.00cp 16328k ps
49 0.00re 0.00cp 2620k find
42 0.00re 0.00cp 13982k grep
32 0.00re 0.00cp 952k tmpwatch
11 0.01re 0.00cp 13456k sh
11 0.00re 0.00cp 2179k makewhatis*
8 0.01re 0.00cp 2683k sort

[root@qg-dc2-tas_sdi ~]# sa -u |grep testuser #Display output per-user
testuser 0.00 cpu 14726k mem sleep
testuser 0.03 cpu 4248k mem top
testuser 0.00 cpu 22544k mem sshd *
testuser 0.00 cpu 4170k mem id
testuser 0.00 cpu 2586k mem hostname

[root@qg-dc2-tas_sdi ~]# sa -m | grep testuser #Display the number of processes and number of CPU minutes on a per-user basis
testuser 22 8.18re 0.00cp 7654k

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Enable NIS client on linux host

July 2nd, 2014

After you set up NIS server, you need set up NIS client. Here's the steps for enabling NIS client on linux box.

Ensure required packages are installed

rpm -qa|egrep 'yp-tools|ypbind|portmap'

Edit /etc/sysconfig/network

Edit /etc/yp.conf
domain server
domain server

Set NIS domain-name


Set /etc/nsswitch.conf

passwd: files nis
shadow: files nis
group: files nis
hosts: files dns nis
bootparams: nisplus [NOTFOUND=return] files
ethers: files
netmasks: files
networks: files
protocols: files
rpc: files
services: files
netgroup: nisplus
publickey: nisplus
automount: files nisplus
aliases: files nisplus
sudoers: files nis

Make sure the portmap service is running:

service portmap start

chkconfig portmap on

Start ypbind service:

service ypbind start
chkconfig ypbind on

Test it out:

rpcinfo -u localhost ypbind

ypcat passwd|egrep 'username'

If you want to set up sudo privileges for NIS users, then you can refer to this article resolved – /etc/sudoers: syntax error near line 10


If there's firewall between Linux NIS clients and NIS servers, then you should not startup ypbind(chkconfig ypbind off; service ypbind stop), if you startup ypbind, then the box will try to connect to NIS servers without stopping. Your linux box will get stuck and will take a long time for you to log on even as root. This is rule of thumb.

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resolved – /etc/sudoers: syntax error near line 10

July 2nd, 2014

When using /usr/sbin/visudo, after modification, errors occurred:

>>> /etc/sudoers: syntax error near line 10 <<<

Here's line 10:

User_Alias Users_SDITAS = username1, username2

Then I changed it as following:

User_Alias USERS_SDITAS = username1, username2

And now everything is ok. So this means that the alias name must all be uppercase.

1. Here's the explanation about User_Alias Users_SDITAS = username1, username2

The first part is the user,
The second is the terminal from where the user can use sudo command,
The third part is which users he may act as,
The last one, is which commands he may run when using sudo.
For example, root ALL=(ALL) ALL, means the root user can execute from ALL terminals, acting as ALL (any) users, and run ALL (any) command. And USERS_SDITAS ALL=(oracle) NOPASSWD:SETENV: CMD_MIGRATIONDC1DC3 means users in group USERS_SDITAS can execute from ALL terminals, acting as oracle user, and run commands in group CMD_MIGRATIONDC1DC3. (sudo -E -u oracle <command>, -E will pass invoking users env variables to target user if SETENV tag is added to sudo commands in /etc/sudoers. You'll get error message "sudo: sorry, you are not allowed to preserve the environment" if you did not add SETENV tag in /etc/sudoers. You can run sudo -l or sudo -ll to get a list of privilege commands for you or for others if you run sudo -l -U <username> )

2. One sample of /etc/sudoers configuration in linux(use visudo to edit, as visudo can check for errors after modification. You may need set "echo 'export PATH=/usr/bin:$PATH' >> /etc/profile" in some circumstances so that sudo will be /usr/bin/sudo):

Defaults logfile=/var/log/sudo.log

Defaults always_set_home #switched to target user's home directory when running sudo. Note that HOME is already set when the the env_reset option is enabled, so always_set_home is only effective for configurations where either env_reset is disabled(Defaults !env_reset) or HOME is present in the env_keep list(Defaults env_keep += HOME). This flag is off by default.
Host_Alias HOSTS_MIGRATIONDC1DC3 = slcn06vmf0012, slcn06vmf0013
Cmnd_Alias CMD_MIGRATIONDC1DC3 = /u01/local/wls/user_projects/domains/base_domain/bin/tasctl, /u01/shared/wls/Oracle_SDI1/sdictl/
User_Alias USERS_SDITAS =username1, username2
USERS_SDITAS ALL=(ALL) NOPASSWD: /bin/su - oracle #users in USERS_SDITAS group can now sudo su - oracle without asking for a password
oracle ALL=(ALL) NOPASSWD:SETENV: CMD_MIGRATIONDC1DC3 #oracle user can run all commands in commands group CMD_MIGRATIONDC1DC3.

3. To check  whether some NIS users are using/bin/false shell(means they can not log on the host by ssh), use the following commands:

ypcat passwd|awk -F: '{if($1 ~ /^username1$|^username2$/) print}'|grep false

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