Kirk Bocek wrote: >Just discovered that on CentOS 4.1 when you issue the command: > > lvcreate -s -n temp -L2G /dev/vgname/lvname > >to create a snapshot, you get the error message: > > snapshot: Required device-mapper target(s) not detected in your kernel > >I've checked and recheck my spelling and tried using the device created >under /dev/mapper. I've tried it on both x86_64 and on i386. Works as >expected under CentOS 3.5. > >Any ideas what is going on? > >_______________________________________________ >CentOS mailing list >CentOS at centos.org >http://lists.centos.org/mailman/listinfo/centos > > I had exactly the same errors when I was using release candidates of 4.0. 4.0 final fixed the problem. I just tried it on 4.1 x86_64; [root at services log]# lvcreate -s -n temp -L2G /dev/VolGroup00/tmplv Logical volume "temp" created but when I tried to remove it, there was a problem; lvremove: page allocation failure. order:0, mode:0xd0 Call Trace:<ffffffff801651b3>{__alloc_pages+709} <ffffffffa006464f>{:dm_mod:kcopyd_client_create+586} <ffffffffa00bc49d>{:dm_snapshot:snapshot_ctr+761} <ffffffffa005fce4>{:dm_mod:dm_table_add_target+328} <ffffffffa0061e7f>{:dm_mod:table_load+225} <ffffffffa0061d9e>{:dm_mod:table_load+0} <ffffffffa00627f2>{:dm_mod:ctl_ioctl+585} <ffffffff8019c22a>{sys_ioctl+1006} <ffffffff801108c6>{system_call+126} Mem-info: DMA per-cpu: cpu 0 hot: low 2, high 6, batch 1 cpu 0 cold: low 0, high 2, batch 1 Normal per-cpu: cpu 0 hot: low 32, high 96, batch 16 cpu 0 cold: low 0, high 32, batch 16 HighMem per-cpu: empty Free pages: 11712kB (0kB HighMem) Active:48508 inactive:24962 dirty:80 writeback:0 unstable:0 free:2928 slab:30118 mapped:33239 pagetables:916 DMA free:11712kB min:20kB low:40kB high:60kB active:0kB inactive:0kB present:16384kB pages_scanned:199 all_unreclaimable? yes protections[]: 0 0 0 Normal free:0kB min:688kB low:1376kB high:2064kB active:194032kB inactive:99848kB present:507648kB pages_scanned:0 all_unreclaimable? no protections[]: 0 0 0 HighMem free:0kB min:128kB low:256kB high:384kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no protections[]: 0 0 0 DMA: 4*4kB 2*8kB 6*16kB 2*32kB 4*64kB 2*128kB 1*256kB 1*512kB 0*1024kB 1*2048kB 2*4096kB = 11712kB Normal: 0*4kB 0*8kB 0*16kB 0*32kB 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 0kB HighMem: empty Swap cache: add 67, delete 47, find 7/10, race 0+0 Free swap: 2096996kB 131008 pages of RAM 20213 reserved pages 36877 pages shared 20 pages swap cached device-mapper: Could not create kcopyd client device-mapper: error adding target to table and 4.1 i386; [root at inetmail ~]# lvcreate -s -n temp -L10m /dev/VolGroup00/usrlv Rounding up size to full physical extent 32.00 MB Logical volume "temp" created [root at inetmail ~]# lvremove /dev/VolGroup00/temp Do you really want to remove active logical volume "temp"? [y/n]: y Logical volume "temp" successfully removed [root at inetmail ~]# Hope this helps.