I learned this the hard way. In Linux, killall kills process by name whereas in Unix System V, killall does what is it is called- kill all processes. killall5 is the SystemV killall command in Linux. If you run killall5 in Linux, it will kill all processes except kernel threads(those surrounded by square bracket in ps aux output) and your login shell.
man killall5: Continue reading
This post applies to RHEL 6 and RHEL 7. I changed the nproc limit for a user to 16383 in /etc/security/limits.conf.
cat >> /etc/security/limits.conf
username soft nproc 16383
When I checked it with ulimits -n, it isn’t working.
su - username
This is because, to prevent a fork bomb, the default limits for all users except root is set to 1024 in RHEL 6. The setting is in /etc/security/limits.d/90-nproc.conf which overrides /etc/security/limits.conf. Continue reading
On creating a new partition in RHEL 6, you might see these messages:
WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
You will also not be able to create filesystem on the new partition. Continue reading
I am unable to extract an xz tarball in RHEL 5.
# tar Jxvf my_archive.tar.xz
tar: invalid option -- J
Try `tar --help' or `tar --usage' for more information.
# tar --version
tar (GNU tar) 1.15.1
Use unxz to uncompress the file and extract it with tar xvf
tar xvf my_archive.tar
NTP is not synchronized and you get “/etc/ntp/ntp.drift.TEMP: Permission denied” in /var/log/messages. This is because ntpd which run as ntp user does not have write permission to /etc/ntp. Change driftfile location to /var/lib/ntp/drift which is preferred or any directory where ntp has read,write permission.
NTP is not synchronised